1 /*
2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util;
27 import java.io.Serializable;
28 import java.io.ObjectOutputStream;
29 import java.io.IOException;
30 import java.io.InvalidObjectException;
31 import java.lang.reflect.Array;
32 import java.util.function.BiConsumer;
33 import java.util.function.BiFunction;
34 import java.util.function.Consumer;
35 import java.util.function.Function;
36 import java.util.function.Predicate;
37 import java.util.function.UnaryOperator;
38
39 /**
40 * This class consists exclusively of static methods that operate on or return
41 * collections. It contains polymorphic algorithms that operate on
42 * collections, "wrappers", which return a new collection backed by a
43 * specified collection, and a few other odds and ends.
44 *
45 * <p>The methods of this class all throw a <tt>NullPointerException</tt>
46 * if the collections or class objects provided to them are null.
47 *
48 * <p>The documentation for the polymorphic algorithms contained in this class
49 * generally includes a brief description of the <i>implementation</i>. Such
50 * descriptions should be regarded as <i>implementation notes</i>, rather than
51 * parts of the <i>specification</i>. Implementors should feel free to
52 * substitute other algorithms, so long as the specification itself is adhered
53 * to. (For example, the algorithm used by <tt>sort</tt> does not have to be
54 * a mergesort, but it does have to be <i>stable</i>.)
55 *
56 * <p>The "destructive" algorithms contained in this class, that is, the
57 * algorithms that modify the collection on which they operate, are specified
58 * to throw <tt>UnsupportedOperationException</tt> if the collection does not
59 * support the appropriate mutation primitive(s), such as the <tt>set</tt>
60 * method. These algorithms may, but are not required to, throw this
61 * exception if an invocation would have no effect on the collection. For
62 * example, invoking the <tt>sort</tt> method on an unmodifiable list that is
63 * already sorted may or may not throw <tt>UnsupportedOperationException</tt>.
64 *
65 * <p>This class is a member of the
66 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
67 * Java Collections Framework</a>.
68 *
69 * @author Josh Bloch
70 * @author Neal Gafter
71 * @see Collection
72 * @see Set
73 * @see List
74 * @see Map
75 * @since 1.2
76 */
77
78 public class Collections {
79 // Suppresses default constructor, ensuring non-instantiability.
80 private Collections() {
81 }
82
83 // Algorithms
84
85 /*
86 * Tuning parameters for algorithms - Many of the List algorithms have
87 * two implementations, one of which is appropriate for RandomAccess
88 * lists, the other for "sequential." Often, the random access variant
89 * yields better performance on small sequential access lists. The
90 * tuning parameters below determine the cutoff point for what constitutes
91 * a "small" sequential access list for each algorithm. The values below
92 * were empirically determined to work well for LinkedList. Hopefully
93 * they should be reasonable for other sequential access List
94 * implementations. Those doing performance work on this code would
95 * do well to validate the values of these parameters from time to time.
96 * (The first word of each tuning parameter name is the algorithm to which
97 * it applies.)
98 */
99 private static final int BINARYSEARCH_THRESHOLD = 5000;
100 private static final int REVERSE_THRESHOLD = 18;
101 private static final int SHUFFLE_THRESHOLD = 5;
102 private static final int FILL_THRESHOLD = 25;
103 private static final int ROTATE_THRESHOLD = 100;
104 private static final int COPY_THRESHOLD = 10;
105 private static final int REPLACEALL_THRESHOLD = 11;
106 private static final int INDEXOFSUBLIST_THRESHOLD = 35;
107
108 /**
109 * Sorts the specified list into ascending order, according to the
110 * {@linkplain Comparable natural ordering} of its elements.
111 * All elements in the list must implement the {@link Comparable}
112 * interface. Furthermore, all elements in the list must be
113 * <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)}
114 * must not throw a {@code ClassCastException} for any elements
115 * {@code e1} and {@code e2} in the list).
116 *
117 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will
118 * not be reordered as a result of the sort.
119 *
120 * <p>The specified list must be modifiable, but need not be resizable.
121 *
122 * <p>Implementation note: This implementation is a stable, adaptive,
123 * iterative mergesort that requires far fewer than n lg(n) comparisons
124 * when the input array is partially sorted, while offering the
125 * performance of a traditional mergesort when the input array is
126 * randomly ordered. If the input array is nearly sorted, the
127 * implementation requires approximately n comparisons. Temporary
128 * storage requirements vary from a small constant for nearly sorted
129 * input arrays to n/2 object references for randomly ordered input
130 * arrays.
131 *
132 * <p>The implementation takes equal advantage of ascending and
133 * descending order in its input array, and can take advantage of
134 * ascending and descending order in different parts of the same
135 * input array. It is well-suited to merging two or more sorted arrays:
136 * simply concatenate the arrays and sort the resulting array.
137 *
138 * <p>The implementation was adapted from Tim Peters's list sort for Python
139 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
140 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
141 * Sorting and Information Theoretic Complexity", in Proceedings of the
142 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
143 * January 1993.
144 *
145 * <p>This implementation dumps the specified list into an array, sorts
146 * the array, and iterates over the list resetting each element
147 * from the corresponding position in the array. This avoids the
148 * n<sup>2</sup> log(n) performance that would result from attempting
149 * to sort a linked list in place.
150 *
151 * @param list the list to be sorted.
152 * @throws ClassCastException if the list contains elements that are not
153 * <i>mutually comparable</i> (for example, strings and integers).
154 * @throws UnsupportedOperationException if the specified list's
155 * list-iterator does not support the {@code set} operation.
156 * @throws IllegalArgumentException (optional) if the implementation
157 * detects that the natural ordering of the list elements is
158 * found to violate the {@link Comparable} contract
159 */
160 @SuppressWarnings("unchecked")
161 public static <T extends Comparable<? super T>> void sort(List<T> list) {
162 Object[] a = list.toArray();
163 Arrays.sort(a);
164 ListIterator<T> i = list.listIterator();
165 for (int j=0; j<a.length; j++) {
166 i.next();
167 i.set((T)a[j]);
168 }
169 }
170
171 /**
172 * Sorts the specified list according to the order induced by the
173 * specified comparator. All elements in the list must be <i>mutually
174 * comparable</i> using the specified comparator (that is,
175 * {@code c.compare(e1, e2)} must not throw a {@code ClassCastException}
176 * for any elements {@code e1} and {@code e2} in the list).
177 *
178 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will
179 * not be reordered as a result of the sort.
180 *
181 * <p>The specified list must be modifiable, but need not be resizable.
182 *
183 * <p>Implementation note: This implementation is a stable, adaptive,
184 * iterative mergesort that requires far fewer than n lg(n) comparisons
185 * when the input array is partially sorted, while offering the
186 * performance of a traditional mergesort when the input array is
187 * randomly ordered. If the input array is nearly sorted, the
188 * implementation requires approximately n comparisons. Temporary
189 * storage requirements vary from a small constant for nearly sorted
190 * input arrays to n/2 object references for randomly ordered input
191 * arrays.
192 *
193 * <p>The implementation takes equal advantage of ascending and
194 * descending order in its input array, and can take advantage of
195 * ascending and descending order in different parts of the same
196 * input array. It is well-suited to merging two or more sorted arrays:
197 * simply concatenate the arrays and sort the resulting array.
198 *
199 * <p>The implementation was adapted from Tim Peters's list sort for Python
200 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
201 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
202 * Sorting and Information Theoretic Complexity", in Proceedings of the
203 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
204 * January 1993.
205 *
206 * <p>This implementation dumps the specified list into an array, sorts
207 * the array, and iterates over the list resetting each element
208 * from the corresponding position in the array. This avoids the
209 * n<sup>2</sup> log(n) performance that would result from attempting
210 * to sort a linked list in place.
211 *
212 * @param list the list to be sorted.
213 * @param c the comparator to determine the order of the list. A
214 * {@code null} value indicates that the elements' <i>natural
215 * ordering</i> should be used.
216 * @throws ClassCastException if the list contains elements that are not
217 * <i>mutually comparable</i> using the specified comparator.
218 * @throws UnsupportedOperationException if the specified list's
219 * list-iterator does not support the {@code set} operation.
220 * @throws IllegalArgumentException (optional) if the comparator is
221 * found to violate the {@link Comparator} contract
222 */
223 @SuppressWarnings({"unchecked", "rawtypes"})
224 public static <T> void sort(List<T> list, Comparator<? super T> c) {
225 Object[] a = list.toArray();
226 Arrays.sort(a, (Comparator)c);
227 ListIterator<T> i = list.listIterator();
228 for (int j=0; j<a.length; j++) {
229 i.next();
230 i.set((T)a[j]);
231 }
232 }
233
234
235 /**
236 * Searches the specified list for the specified object using the binary
237 * search algorithm. The list must be sorted into ascending order
238 * according to the {@linkplain Comparable natural ordering} of its
239 * elements (as by the {@link #sort(List)} method) prior to making this
240 * call. If it is not sorted, the results are undefined. If the list
241 * contains multiple elements equal to the specified object, there is no
242 * guarantee which one will be found.
243 *
244 * <p>This method runs in log(n) time for a "random access" list (which
245 * provides near-constant-time positional access). If the specified list
246 * does not implement the {@link RandomAccess} interface and is large,
247 * this method will do an iterator-based binary search that performs
248 * O(n) link traversals and O(log n) element comparisons.
249 *
250 * @param list the list to be searched.
251 * @param key the key to be searched for.
252 * @return the index of the search key, if it is contained in the list;
253 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
254 * <i>insertion point</i> is defined as the point at which the
255 * key would be inserted into the list: the index of the first
256 * element greater than the key, or <tt>list.size()</tt> if all
257 * elements in the list are less than the specified key. Note
258 * that this guarantees that the return value will be >= 0 if
259 * and only if the key is found.
260 * @throws ClassCastException if the list contains elements that are not
261 * <i>mutually comparable</i> (for example, strings and
262 * integers), or the search key is not mutually comparable
263 * with the elements of the list.
264 */
265 public static <T>
266 int binarySearch(List<? extends Comparable<? super T>> list, T key) {
267 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
268 return Collections.indexedBinarySearch(list, key);
269 else
270 return Collections.iteratorBinarySearch(list, key);
271 }
272
273 private static <T>
274 int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) {
275 int low = 0;
276 int high = list.size()-1;
277
278 while (low <= high) {
279 int mid = (low + high) >>> 1;
280 Comparable<? super T> midVal = list.get(mid);
281 int cmp = midVal.compareTo(key);
282
283 if (cmp < 0)
284 low = mid + 1;
285 else if (cmp > 0)
286 high = mid - 1;
287 else
288 return mid; // key found
289 }
290 return -(low + 1); // key not found
291 }
292
293 private static <T>
294 int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
295 {
296 int low = 0;
297 int high = list.size()-1;
298 ListIterator<? extends Comparable<? super T>> i = list.listIterator();
299
300 while (low <= high) {
301 int mid = (low + high) >>> 1;
302 Comparable<? super T> midVal = get(i, mid);
303 int cmp = midVal.compareTo(key);
304
305 if (cmp < 0)
306 low = mid + 1;
307 else if (cmp > 0)
308 high = mid - 1;
309 else
310 return mid; // key found
311 }
312 return -(low + 1); // key not found
313 }
314
315 /**
316 * Gets the ith element from the given list by repositioning the specified
317 * list listIterator.
318 */
319 private static <T> T get(ListIterator<? extends T> i, int index) {
320 T obj = null;
321 int pos = i.nextIndex();
322 if (pos <= index) {
323 do {
324 obj = i.next();
325 } while (pos++ < index);
326 } else {
327 do {
328 obj = i.previous();
329 } while (--pos > index);
330 }
331 return obj;
332 }
333
334 /**
335 * Searches the specified list for the specified object using the binary
336 * search algorithm. The list must be sorted into ascending order
337 * according to the specified comparator (as by the
338 * {@link #sort(List, Comparator) sort(List, Comparator)}
339 * method), prior to making this call. If it is
340 * not sorted, the results are undefined. If the list contains multiple
341 * elements equal to the specified object, there is no guarantee which one
342 * will be found.
343 *
344 * <p>This method runs in log(n) time for a "random access" list (which
345 * provides near-constant-time positional access). If the specified list
346 * does not implement the {@link RandomAccess} interface and is large,
347 * this method will do an iterator-based binary search that performs
348 * O(n) link traversals and O(log n) element comparisons.
349 *
350 * @param list the list to be searched.
351 * @param key the key to be searched for.
352 * @param c the comparator by which the list is ordered.
353 * A <tt>null</tt> value indicates that the elements'
354 * {@linkplain Comparable natural ordering} should be used.
355 * @return the index of the search key, if it is contained in the list;
356 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
357 * <i>insertion point</i> is defined as the point at which the
358 * key would be inserted into the list: the index of the first
359 * element greater than the key, or <tt>list.size()</tt> if all
360 * elements in the list are less than the specified key. Note
361 * that this guarantees that the return value will be >= 0 if
362 * and only if the key is found.
363 * @throws ClassCastException if the list contains elements that are not
364 * <i>mutually comparable</i> using the specified comparator,
365 * or the search key is not mutually comparable with the
366 * elements of the list using this comparator.
367 */
368 @SuppressWarnings("unchecked")
369 public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
370 if (c==null)
371 return binarySearch((List<? extends Comparable<? super T>>) list, key);
372
373 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
374 return Collections.indexedBinarySearch(list, key, c);
375 else
376 return Collections.iteratorBinarySearch(list, key, c);
377 }
378
379 private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
380 int low = 0;
381 int high = l.size()-1;
382
383 while (low <= high) {
384 int mid = (low + high) >>> 1;
385 T midVal = l.get(mid);
386 int cmp = c.compare(midVal, key);
387
388 if (cmp < 0)
389 low = mid + 1;
390 else if (cmp > 0)
391 high = mid - 1;
392 else
393 return mid; // key found
394 }
395 return -(low + 1); // key not found
396 }
397
398 private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
399 int low = 0;
400 int high = l.size()-1;
401 ListIterator<? extends T> i = l.listIterator();
402
403 while (low <= high) {
404 int mid = (low + high) >>> 1;
405 T midVal = get(i, mid);
406 int cmp = c.compare(midVal, key);
407
408 if (cmp < 0)
409 low = mid + 1;
410 else if (cmp > 0)
411 high = mid - 1;
412 else
413 return mid; // key found
414 }
415 return -(low + 1); // key not found
416 }
417
418 /**
419 * Reverses the order of the elements in the specified list.<p>
420 *
421 * This method runs in linear time.
422 *
423 * @param list the list whose elements are to be reversed.
424 * @throws UnsupportedOperationException if the specified list or
425 * its list-iterator does not support the <tt>set</tt> operation.
426 */
427 @SuppressWarnings({"rawtypes", "unchecked"})
428 public static void reverse(List<?> list) {
429 int size = list.size();
430 if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
431 for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
432 swap(list, i, j);
433 } else {
434 // instead of using a raw type here, it's possible to capture
435 // the wildcard but it will require a call to a supplementary
436 // private method
437 ListIterator fwd = list.listIterator();
438 ListIterator rev = list.listIterator(size);
439 for (int i=0, mid=list.size()>>1; i<mid; i++) {
440 Object tmp = fwd.next();
441 fwd.set(rev.previous());
442 rev.set(tmp);
443 }
444 }
445 }
446
447 /**
448 * Randomly permutes the specified list using a default source of
449 * randomness. All permutations occur with approximately equal
450 * likelihood.
451 *
452 * <p>The hedge "approximately" is used in the foregoing description because
453 * default source of randomness is only approximately an unbiased source
454 * of independently chosen bits. If it were a perfect source of randomly
455 * chosen bits, then the algorithm would choose permutations with perfect
456 * uniformity.
457 *
458 * <p>This implementation traverses the list backwards, from the last
459 * element up to the second, repeatedly swapping a randomly selected element
460 * into the "current position". Elements are randomly selected from the
461 * portion of the list that runs from the first element to the current
462 * position, inclusive.
463 *
464 * <p>This method runs in linear time. If the specified list does not
465 * implement the {@link RandomAccess} interface and is large, this
466 * implementation dumps the specified list into an array before shuffling
467 * it, and dumps the shuffled array back into the list. This avoids the
468 * quadratic behavior that would result from shuffling a "sequential
469 * access" list in place.
470 *
471 * @param list the list to be shuffled.
472 * @throws UnsupportedOperationException if the specified list or
473 * its list-iterator does not support the <tt>set</tt> operation.
474 */
475 public static void shuffle(List<?> list) {
476 Random rnd = r;
477 if (rnd == null)
478 r = rnd = new Random(); // harmless race.
479 shuffle(list, rnd);
480 }
481
482 private static Random r;
483
484 /**
485 * Randomly permute the specified list using the specified source of
486 * randomness. All permutations occur with equal likelihood
487 * assuming that the source of randomness is fair.<p>
488 *
489 * This implementation traverses the list backwards, from the last element
490 * up to the second, repeatedly swapping a randomly selected element into
491 * the "current position". Elements are randomly selected from the
492 * portion of the list that runs from the first element to the current
493 * position, inclusive.<p>
494 *
495 * This method runs in linear time. If the specified list does not
496 * implement the {@link RandomAccess} interface and is large, this
497 * implementation dumps the specified list into an array before shuffling
498 * it, and dumps the shuffled array back into the list. This avoids the
499 * quadratic behavior that would result from shuffling a "sequential
500 * access" list in place.
501 *
502 * @param list the list to be shuffled.
503 * @param rnd the source of randomness to use to shuffle the list.
504 * @throws UnsupportedOperationException if the specified list or its
505 * list-iterator does not support the <tt>set</tt> operation.
506 */
507 @SuppressWarnings({"rawtypes", "unchecked"})
508 public static void shuffle(List<?> list, Random rnd) {
509 int size = list.size();
510 if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
511 for (int i=size; i>1; i--)
512 swap(list, i-1, rnd.nextInt(i));
513 } else {
514 Object arr[] = list.toArray();
515
516 // Shuffle array
517 for (int i=size; i>1; i--)
518 swap(arr, i-1, rnd.nextInt(i));
519
520 // Dump array back into list
521 // instead of using a raw type here, it's possible to capture
522 // the wildcard but it will require a call to a supplementary
523 // private method
524 ListIterator it = list.listIterator();
525 for (int i=0; i<arr.length; i++) {
526 it.next();
527 it.set(arr[i]);
528 }
529 }
530 }
531
532 /**
533 * Swaps the elements at the specified positions in the specified list.
534 * (If the specified positions are equal, invoking this method leaves
535 * the list unchanged.)
536 *
537 * @param list The list in which to swap elements.
538 * @param i the index of one element to be swapped.
539 * @param j the index of the other element to be swapped.
540 * @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt>
541 * is out of range (i < 0 || i >= list.size()
542 * || j < 0 || j >= list.size()).
543 * @since 1.4
544 */
545 @SuppressWarnings({"rawtypes", "unchecked"})
546 public static void swap(List<?> list, int i, int j) {
547 // instead of using a raw type here, it's possible to capture
548 // the wildcard but it will require a call to a supplementary
549 // private method
550 final List l = list;
551 l.set(i, l.set(j, l.get(i)));
552 }
553
554 /**
555 * Swaps the two specified elements in the specified array.
556 */
557 private static void swap(Object[] arr, int i, int j) {
558 Object tmp = arr[i];
559 arr[i] = arr[j];
560 arr[j] = tmp;
561 }
562
563 /**
564 * Replaces all of the elements of the specified list with the specified
565 * element. <p>
566 *
567 * This method runs in linear time.
568 *
569 * @param list the list to be filled with the specified element.
570 * @param obj The element with which to fill the specified list.
571 * @throws UnsupportedOperationException if the specified list or its
572 * list-iterator does not support the <tt>set</tt> operation.
573 */
574 public static <T> void fill(List<? super T> list, T obj) {
575 int size = list.size();
576
577 if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
578 for (int i=0; i<size; i++)
579 list.set(i, obj);
580 } else {
581 ListIterator<? super T> itr = list.listIterator();
582 for (int i=0; i<size; i++) {
583 itr.next();
584 itr.set(obj);
585 }
586 }
587 }
588
589 /**
590 * Copies all of the elements from one list into another. After the
591 * operation, the index of each copied element in the destination list
592 * will be identical to its index in the source list. The destination
593 * list must be at least as long as the source list. If it is longer, the
594 * remaining elements in the destination list are unaffected. <p>
595 *
596 * This method runs in linear time.
597 *
598 * @param dest The destination list.
599 * @param src The source list.
600 * @throws IndexOutOfBoundsException if the destination list is too small
601 * to contain the entire source List.
602 * @throws UnsupportedOperationException if the destination list's
603 * list-iterator does not support the <tt>set</tt> operation.
604 */
605 public static <T> void copy(List<? super T> dest, List<? extends T> src) {
606 int srcSize = src.size();
607 if (srcSize > dest.size())
608 throw new IndexOutOfBoundsException("Source does not fit in dest");
609
610 if (srcSize < COPY_THRESHOLD ||
611 (src instanceof RandomAccess && dest instanceof RandomAccess)) {
612 for (int i=0; i<srcSize; i++)
613 dest.set(i, src.get(i));
614 } else {
615 ListIterator<? super T> di=dest.listIterator();
616 ListIterator<? extends T> si=src.listIterator();
617 for (int i=0; i<srcSize; i++) {
618 di.next();
619 di.set(si.next());
620 }
621 }
622 }
623
624 /**
625 * Returns the minimum element of the given collection, according to the
626 * <i>natural ordering</i> of its elements. All elements in the
627 * collection must implement the <tt>Comparable</tt> interface.
628 * Furthermore, all elements in the collection must be <i>mutually
629 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
630 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
631 * <tt>e2</tt> in the collection).<p>
632 *
633 * This method iterates over the entire collection, hence it requires
634 * time proportional to the size of the collection.
635 *
636 * @param coll the collection whose minimum element is to be determined.
637 * @return the minimum element of the given collection, according
638 * to the <i>natural ordering</i> of its elements.
639 * @throws ClassCastException if the collection contains elements that are
640 * not <i>mutually comparable</i> (for example, strings and
641 * integers).
642 * @throws NoSuchElementException if the collection is empty.
643 * @see Comparable
644 */
645 public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
646 Iterator<? extends T> i = coll.iterator();
647 T candidate = i.next();
648
649 while (i.hasNext()) {
650 T next = i.next();
651 if (next.compareTo(candidate) < 0)
652 candidate = next;
653 }
654 return candidate;
655 }
656
657 /**
658 * Returns the minimum element of the given collection, according to the
659 * order induced by the specified comparator. All elements in the
660 * collection must be <i>mutually comparable</i> by the specified
661 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
662 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
663 * <tt>e2</tt> in the collection).<p>
664 *
665 * This method iterates over the entire collection, hence it requires
666 * time proportional to the size of the collection.
667 *
668 * @param coll the collection whose minimum element is to be determined.
669 * @param comp the comparator with which to determine the minimum element.
670 * A <tt>null</tt> value indicates that the elements' <i>natural
671 * ordering</i> should be used.
672 * @return the minimum element of the given collection, according
673 * to the specified comparator.
674 * @throws ClassCastException if the collection contains elements that are
675 * not <i>mutually comparable</i> using the specified comparator.
676 * @throws NoSuchElementException if the collection is empty.
677 * @see Comparable
678 */
679 @SuppressWarnings({"unchecked", "rawtypes"})
680 public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
681 if (comp==null)
682 return (T)min((Collection) coll);
683
684 Iterator<? extends T> i = coll.iterator();
685 T candidate = i.next();
686
687 while (i.hasNext()) {
688 T next = i.next();
689 if (comp.compare(next, candidate) < 0)
690 candidate = next;
691 }
692 return candidate;
693 }
694
695 /**
696 * Returns the maximum element of the given collection, according to the
697 * <i>natural ordering</i> of its elements. All elements in the
698 * collection must implement the <tt>Comparable</tt> interface.
699 * Furthermore, all elements in the collection must be <i>mutually
700 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
701 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
702 * <tt>e2</tt> in the collection).<p>
703 *
704 * This method iterates over the entire collection, hence it requires
705 * time proportional to the size of the collection.
706 *
707 * @param coll the collection whose maximum element is to be determined.
708 * @return the maximum element of the given collection, according
709 * to the <i>natural ordering</i> of its elements.
710 * @throws ClassCastException if the collection contains elements that are
711 * not <i>mutually comparable</i> (for example, strings and
712 * integers).
713 * @throws NoSuchElementException if the collection is empty.
714 * @see Comparable
715 */
716 public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
717 Iterator<? extends T> i = coll.iterator();
718 T candidate = i.next();
719
720 while (i.hasNext()) {
721 T next = i.next();
722 if (next.compareTo(candidate) > 0)
723 candidate = next;
724 }
725 return candidate;
726 }
727
728 /**
729 * Returns the maximum element of the given collection, according to the
730 * order induced by the specified comparator. All elements in the
731 * collection must be <i>mutually comparable</i> by the specified
732 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
733 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
734 * <tt>e2</tt> in the collection).<p>
735 *
736 * This method iterates over the entire collection, hence it requires
737 * time proportional to the size of the collection.
738 *
739 * @param coll the collection whose maximum element is to be determined.
740 * @param comp the comparator with which to determine the maximum element.
741 * A <tt>null</tt> value indicates that the elements' <i>natural
742 * ordering</i> should be used.
743 * @return the maximum element of the given collection, according
744 * to the specified comparator.
745 * @throws ClassCastException if the collection contains elements that are
746 * not <i>mutually comparable</i> using the specified comparator.
747 * @throws NoSuchElementException if the collection is empty.
748 * @see Comparable
749 */
750 @SuppressWarnings({"unchecked", "rawtypes"})
751 public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
752 if (comp==null)
753 return (T)max((Collection) coll);
754
755 Iterator<? extends T> i = coll.iterator();
756 T candidate = i.next();
757
758 while (i.hasNext()) {
759 T next = i.next();
760 if (comp.compare(next, candidate) > 0)
761 candidate = next;
762 }
763 return candidate;
764 }
765
766 /**
767 * Rotates the elements in the specified list by the specified distance.
768 * After calling this method, the element at index <tt>i</tt> will be
769 * the element previously at index <tt>(i - distance)</tt> mod
770 * <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt>
771 * and <tt>list.size()-1</tt>, inclusive. (This method has no effect on
772 * the size of the list.)
773 *
774 * <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>.
775 * After invoking <tt>Collections.rotate(list, 1)</tt> (or
776 * <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise
777 * <tt>[s, t, a, n, k]</tt>.
778 *
779 * <p>Note that this method can usefully be applied to sublists to
780 * move one or more elements within a list while preserving the
781 * order of the remaining elements. For example, the following idiom
782 * moves the element at index <tt>j</tt> forward to position
783 * <tt>k</tt> (which must be greater than or equal to <tt>j</tt>):
784 * <pre>
785 * Collections.rotate(list.subList(j, k+1), -1);
786 * </pre>
787 * To make this concrete, suppose <tt>list</tt> comprises
788 * <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt>
789 * (<tt>b</tt>) forward two positions, perform the following invocation:
790 * <pre>
791 * Collections.rotate(l.subList(1, 4), -1);
792 * </pre>
793 * The resulting list is <tt>[a, c, d, b, e]</tt>.
794 *
795 * <p>To move more than one element forward, increase the absolute value
796 * of the rotation distance. To move elements backward, use a positive
797 * shift distance.
798 *
799 * <p>If the specified list is small or implements the {@link
800 * RandomAccess} interface, this implementation exchanges the first
801 * element into the location it should go, and then repeatedly exchanges
802 * the displaced element into the location it should go until a displaced
803 * element is swapped into the first element. If necessary, the process
804 * is repeated on the second and successive elements, until the rotation
805 * is complete. If the specified list is large and doesn't implement the
806 * <tt>RandomAccess</tt> interface, this implementation breaks the
807 * list into two sublist views around index <tt>-distance mod size</tt>.
808 * Then the {@link #reverse(List)} method is invoked on each sublist view,
809 * and finally it is invoked on the entire list. For a more complete
810 * description of both algorithms, see Section 2.3 of Jon Bentley's
811 * <i>Programming Pearls</i> (Addison-Wesley, 1986).
812 *
813 * @param list the list to be rotated.
814 * @param distance the distance to rotate the list. There are no
815 * constraints on this value; it may be zero, negative, or
816 * greater than <tt>list.size()</tt>.
817 * @throws UnsupportedOperationException if the specified list or
818 * its list-iterator does not support the <tt>set</tt> operation.
819 * @since 1.4
820 */
821 public static void rotate(List<?> list, int distance) {
822 if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
823 rotate1(list, distance);
824 else
825 rotate2(list, distance);
826 }
827
828 private static <T> void rotate1(List<T> list, int distance) {
829 int size = list.size();
830 if (size == 0)
831 return;
832 distance = distance % size;
833 if (distance < 0)
834 distance += size;
835 if (distance == 0)
836 return;
837
838 for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
839 T displaced = list.get(cycleStart);
840 int i = cycleStart;
841 do {
842 i += distance;
843 if (i >= size)
844 i -= size;
845 displaced = list.set(i, displaced);
846 nMoved ++;
847 } while (i != cycleStart);
848 }
849 }
850
851 private static void rotate2(List<?> list, int distance) {
852 int size = list.size();
853 if (size == 0)
854 return;
855 int mid = -distance % size;
856 if (mid < 0)
857 mid += size;
858 if (mid == 0)
859 return;
860
861 reverse(list.subList(0, mid));
862 reverse(list.subList(mid, size));
863 reverse(list);
864 }
865
866 /**
867 * Replaces all occurrences of one specified value in a list with another.
868 * More formally, replaces with <tt>newVal</tt> each element <tt>e</tt>
869 * in <tt>list</tt> such that
870 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
871 * (This method has no effect on the size of the list.)
872 *
873 * @param list the list in which replacement is to occur.
874 * @param oldVal the old value to be replaced.
875 * @param newVal the new value with which <tt>oldVal</tt> is to be
876 * replaced.
877 * @return <tt>true</tt> if <tt>list</tt> contained one or more elements
878 * <tt>e</tt> such that
879 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
880 * @throws UnsupportedOperationException if the specified list or
881 * its list-iterator does not support the <tt>set</tt> operation.
882 * @since 1.4
883 */
884 public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
885 boolean result = false;
886 int size = list.size();
887 if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
888 if (oldVal==null) {
889 for (int i=0; i<size; i++) {
890 if (list.get(i)==null) {
891 list.set(i, newVal);
892 result = true;
893 }
894 }
895 } else {
896 for (int i=0; i<size; i++) {
897 if (oldVal.equals(list.get(i))) {
898 list.set(i, newVal);
899 result = true;
900 }
901 }
902 }
903 } else {
904 ListIterator<T> itr=list.listIterator();
905 if (oldVal==null) {
906 for (int i=0; i<size; i++) {
907 if (itr.next()==null) {
908 itr.set(newVal);
909 result = true;
910 }
911 }
912 } else {
913 for (int i=0; i<size; i++) {
914 if (oldVal.equals(itr.next())) {
915 itr.set(newVal);
916 result = true;
917 }
918 }
919 }
920 }
921 return result;
922 }
923
924 /**
925 * Returns the starting position of the first occurrence of the specified
926 * target list within the specified source list, or -1 if there is no
927 * such occurrence. More formally, returns the lowest index <tt>i</tt>
928 * such that <tt>source.subList(i, i+target.size()).equals(target)</tt>,
929 * or -1 if there is no such index. (Returns -1 if
930 * <tt>target.size() > source.size()</tt>.)
931 *
932 * <p>This implementation uses the "brute force" technique of scanning
933 * over the source list, looking for a match with the target at each
934 * location in turn.
935 *
936 * @param source the list in which to search for the first occurrence
937 * of <tt>target</tt>.
938 * @param target the list to search for as a subList of <tt>source</tt>.
939 * @return the starting position of the first occurrence of the specified
940 * target list within the specified source list, or -1 if there
941 * is no such occurrence.
942 * @since 1.4
943 */
944 public static int indexOfSubList(List<?> source, List<?> target) {
945 int sourceSize = source.size();
946 int targetSize = target.size();
947 int maxCandidate = sourceSize - targetSize;
948
949 if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
950 (source instanceof RandomAccess&&target instanceof RandomAccess)) {
951 nextCand:
952 for (int candidate = 0; candidate <= maxCandidate; candidate++) {
953 for (int i=0, j=candidate; i<targetSize; i++, j++)
954 if (!eq(target.get(i), source.get(j)))
955 continue nextCand; // Element mismatch, try next cand
956 return candidate; // All elements of candidate matched target
957 }
958 } else { // Iterator version of above algorithm
959 ListIterator<?> si = source.listIterator();
960 nextCand:
961 for (int candidate = 0; candidate <= maxCandidate; candidate++) {
962 ListIterator<?> ti = target.listIterator();
963 for (int i=0; i<targetSize; i++) {
964 if (!eq(ti.next(), si.next())) {
965 // Back up source iterator to next candidate
966 for (int j=0; j<i; j++)
967 si.previous();
968 continue nextCand;
969 }
970 }
971 return candidate;
972 }
973 }
974 return -1; // No candidate matched the target
975 }
976
977 /**
978 * Returns the starting position of the last occurrence of the specified
979 * target list within the specified source list, or -1 if there is no such
980 * occurrence. More formally, returns the highest index <tt>i</tt>
981 * such that <tt>source.subList(i, i+target.size()).equals(target)</tt>,
982 * or -1 if there is no such index. (Returns -1 if
983 * <tt>target.size() > source.size()</tt>.)
984 *
985 * <p>This implementation uses the "brute force" technique of iterating
986 * over the source list, looking for a match with the target at each
987 * location in turn.
988 *
989 * @param source the list in which to search for the last occurrence
990 * of <tt>target</tt>.
991 * @param target the list to search for as a subList of <tt>source</tt>.
992 * @return the starting position of the last occurrence of the specified
993 * target list within the specified source list, or -1 if there
994 * is no such occurrence.
995 * @since 1.4
996 */
997 public static int lastIndexOfSubList(List<?> source, List<?> target) {
998 int sourceSize = source.size();
999 int targetSize = target.size();
1000 int maxCandidate = sourceSize - targetSize;
1001
1002 if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
1003 source instanceof RandomAccess) { // Index access version
1004 nextCand:
1005 for (int candidate = maxCandidate; candidate >= 0; candidate--) {
1006 for (int i=0, j=candidate; i<targetSize; i++, j++)
1007 if (!eq(target.get(i), source.get(j)))
1008 continue nextCand; // Element mismatch, try next cand
1009 return candidate; // All elements of candidate matched target
1010 }
1011 } else { // Iterator version of above algorithm
1012 if (maxCandidate < 0)
1013 return -1;
1014 ListIterator<?> si = source.listIterator(maxCandidate);
1015 nextCand:
1016 for (int candidate = maxCandidate; candidate >= 0; candidate--) {
1017 ListIterator<?> ti = target.listIterator();
1018 for (int i=0; i<targetSize; i++) {
1019 if (!eq(ti.next(), si.next())) {
1020 if (candidate != 0) {
1021 // Back up source iterator to next candidate
1022 for (int j=0; j<=i+1; j++)
1023 si.previous();
1024 }
1025 continue nextCand;
1026 }
1027 }
1028 return candidate;
1029 }
1030 }
1031 return -1; // No candidate matched the target
1032 }
1033
1034
1035 // Unmodifiable Wrappers
1036
1037 /**
1038 * Returns an unmodifiable view of the specified collection. This method
1039 * allows modules to provide users with "read-only" access to internal
1040 * collections. Query operations on the returned collection "read through"
1041 * to the specified collection, and attempts to modify the returned
1042 * collection, whether direct or via its iterator, result in an
1043 * <tt>UnsupportedOperationException</tt>.<p>
1044 *
1045 * The returned collection does <i>not</i> pass the hashCode and equals
1046 * operations through to the backing collection, but relies on
1047 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
1048 * is necessary to preserve the contracts of these operations in the case
1049 * that the backing collection is a set or a list.<p>
1050 *
1051 * The returned collection will be serializable if the specified collection
1052 * is serializable.
1053 *
1054 * @param c the collection for which an unmodifiable view is to be
1055 * returned.
1056 * @return an unmodifiable view of the specified collection.
1057 */
1058 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
1059 return new UnmodifiableCollection<>(c);
1060 }
1061
1062 /**
1063 * @serial include
1064 */
1065 static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
1066 private static final long serialVersionUID = 1820017752578914078L;
1067
1068 final Collection<? extends E> c;
1069
1070 UnmodifiableCollection(Collection<? extends E> c) {
1071 if (c==null)
1072 throw new NullPointerException();
1073 this.c = c;
1074 }
1075
1076 public int size() {return c.size();}
1077 public boolean isEmpty() {return c.isEmpty();}
1078 public boolean contains(Object o) {return c.contains(o);}
1079 public Object[] toArray() {return c.toArray();}
1080 public <T> T[] toArray(T[] a) {return c.toArray(a);}
1081 public String toString() {return c.toString();}
1082
1083 public Iterator<E> iterator() {
1084 return new Iterator<E>() {
1085 private final Iterator<? extends E> i = c.iterator();
1086
1087 public boolean hasNext() {return i.hasNext();}
1088 public E next() {return i.next();}
1089 public void remove() {
1090 throw new UnsupportedOperationException();
1091 }
1092 @Override
1093 public void forEachRemaining(Consumer<? super E> action) {
1094 // Use backing collection version
1095 i.forEachRemaining(action);
1096 }
1097 };
1098 }
1099
1100 public boolean add(E e) {
1101 throw new UnsupportedOperationException();
1102 }
1103 public boolean remove(Object o) {
1104 throw new UnsupportedOperationException();
1105 }
1106
1107 public boolean containsAll(Collection<?> coll) {
1108 return c.containsAll(coll);
1109 }
1110 public boolean addAll(Collection<? extends E> coll) {
1111 throw new UnsupportedOperationException();
1112 }
1113 public boolean removeAll(Collection<?> coll) {
1114 throw new UnsupportedOperationException();
1115 }
1116 public boolean retainAll(Collection<?> coll) {
1117 throw new UnsupportedOperationException();
1118 }
1119 public void clear() {
1120 throw new UnsupportedOperationException();
1121 }
1122
1123 // Override default methods in Collection
1124 @Override
1125 public void forEach(Consumer<? super E> action) {
1126 c.forEach(action);
1127 }
1128 @Override
1129 public boolean removeIf(Predicate<? super E> filter) {
1130 throw new UnsupportedOperationException();
1131 }
1132 @Override
1133 public Spliterator<E> spliterator() {
1134 return (Spliterator<E>)c.spliterator();
1135 }
1136
1137 }
1138
1139 /**
1140 * Returns an unmodifiable view of the specified set. This method allows
1141 * modules to provide users with "read-only" access to internal sets.
1142 * Query operations on the returned set "read through" to the specified
1143 * set, and attempts to modify the returned set, whether direct or via its
1144 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
1145 *
1146 * The returned set will be serializable if the specified set
1147 * is serializable.
1148 *
1149 * @param s the set for which an unmodifiable view is to be returned.
1150 * @return an unmodifiable view of the specified set.
1151 */
1152 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
1153 return new UnmodifiableSet<>(s);
1154 }
1155
1156 /**
1157 * @serial include
1158 */
1159 static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
1160 implements Set<E>, Serializable {
1161 private static final long serialVersionUID = -9215047833775013803L;
1162
1163 UnmodifiableSet(Set<? extends E> s) {super(s);}
1164 public boolean equals(Object o) {return o == this || c.equals(o);}
1165 public int hashCode() {return c.hashCode();}
1166 }
1167
1168 /**
1169 * Returns an unmodifiable view of the specified sorted set. This method
1170 * allows modules to provide users with "read-only" access to internal
1171 * sorted sets. Query operations on the returned sorted set "read
1172 * through" to the specified sorted set. Attempts to modify the returned
1173 * sorted set, whether direct, via its iterator, or via its
1174 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
1175 * an <tt>UnsupportedOperationException</tt>.<p>
1176 *
1177 * The returned sorted set will be serializable if the specified sorted set
1178 * is serializable.
1179 *
1180 * @param s the sorted set for which an unmodifiable view is to be
1181 * returned.
1182 * @return an unmodifiable view of the specified sorted set.
1183 */
1184 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
1185 return new UnmodifiableSortedSet<>(s);
1186 }
1187
1188 /**
1189 * @serial include
1190 */
1191 static class UnmodifiableSortedSet<E>
1192 extends UnmodifiableSet<E>
1193 implements SortedSet<E>, Serializable {
1194 private static final long serialVersionUID = -4929149591599911165L;
1195 private final SortedSet<E> ss;
1196
1197 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
1198
1199 public Comparator<? super E> comparator() {return ss.comparator();}
1200
1201 public SortedSet<E> subSet(E fromElement, E toElement) {
1202 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
1203 }
1204 public SortedSet<E> headSet(E toElement) {
1205 return new UnmodifiableSortedSet<>(ss.headSet(toElement));
1206 }
1207 public SortedSet<E> tailSet(E fromElement) {
1208 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
1209 }
1210
1211 public E first() {return ss.first();}
1212 public E last() {return ss.last();}
1213 }
1214
1215 /**
1216 * Returns an unmodifiable view of the specified navigable set. This method
1217 * allows modules to provide users with "read-only" access to internal
1218 * navigable sets. Query operations on the returned navigable set "read
1219 * through" to the specified navigable set. Attempts to modify the returned
1220 * navigable set, whether direct, via its iterator, or via its
1221 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
1222 * an <tt>UnsupportedOperationException</tt>.<p>
1223 *
1224 * The returned navigable set will be serializable if the specified sorted set
1225 * is serializable.
1226 *
1227 * @param s the navigable set for which an unmodifiable view is to be
1228 * returned
1229 * @return an unmodifiable view of the specified navigable set
1230 * @since 1.8
1231 */
1232 public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
1233 return new UnmodifiableNavigableSet<>(s);
1234 }
1235
1236 /**
1237 * @serial include
1238 */
1239 static class UnmodifiableNavigableSet<E>
1240 extends UnmodifiableSortedSet<E>
1241 implements NavigableSet<E>, Serializable {
1242
1243 private static final long serialVersionUID = -6027448201786391929L;
1244
1245 private final NavigableSet<E> ns;
1246
1247 UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;}
1248
1249 @Override public E lower(E e) { return ns.lower(e); }
1250 @Override public E floor(E e) { return ns.floor(e); }
1251 @Override public E ceiling(E e) { return ns.ceiling(e); }
1252 @Override public E higher(E e) { return ns.higher(e); }
1253 @Override public E pollFirst() { throw new UnsupportedOperationException(); }
1254 @Override public E pollLast() { throw new UnsupportedOperationException(); }
1255 @Override
1256 public NavigableSet<E> descendingSet() {
1257 return new UnmodifiableNavigableSet<>(ns.descendingSet());
1258 }
1259
1260 @Override
1261 public Iterator<E> descendingIterator() {
1262 return descendingSet().iterator();
1263 }
1264
1265 @Override
1266 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
1267 return new UnmodifiableNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
1268 }
1269
1270 @Override
1271 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
1272 return new UnmodifiableNavigableSet<>(ns.headSet(toElement, inclusive));
1273 }
1274
1275 @Override
1276 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
1277 return new UnmodifiableNavigableSet<>(ns.tailSet(fromElement, inclusive));
1278 }
1279 }
1280
1281 /**
1282 * Returns an unmodifiable view of the specified list. This method allows
1283 * modules to provide users with "read-only" access to internal
1284 * lists. Query operations on the returned list "read through" to the
1285 * specified list, and attempts to modify the returned list, whether
1286 * direct or via its iterator, result in an
1287 * <tt>UnsupportedOperationException</tt>.<p>
1288 *
1289 * The returned list will be serializable if the specified list
1290 * is serializable. Similarly, the returned list will implement
1291 * {@link RandomAccess} if the specified list does.
1292 *
1293 * @param list the list for which an unmodifiable view is to be returned.
1294 * @return an unmodifiable view of the specified list.
1295 */
1296 public static <T> List<T> unmodifiableList(List<? extends T> list) {
1297 return (list instanceof RandomAccess ?
1298 new UnmodifiableRandomAccessList<>(list) :
1299 new UnmodifiableList<>(list));
1300 }
1301
1302 /**
1303 * @serial include
1304 */
1305 static class UnmodifiableList<E> extends UnmodifiableCollection<E>
1306 implements List<E> {
1307 private static final long serialVersionUID = -283967356065247728L;
1308
1309 final List<? extends E> list;
1310
1311 UnmodifiableList(List<? extends E> list) {
1312 super(list);
1313 this.list = list;
1314 }
1315
1316 public boolean equals(Object o) {return o == this || list.equals(o);}
1317 public int hashCode() {return list.hashCode();}
1318
1319 public E get(int index) {return list.get(index);}
1320 public E set(int index, E element) {
1321 throw new UnsupportedOperationException();
1322 }
1323 public void add(int index, E element) {
1324 throw new UnsupportedOperationException();
1325 }
1326 public E remove(int index) {
1327 throw new UnsupportedOperationException();
1328 }
1329 public int indexOf(Object o) {return list.indexOf(o);}
1330 public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
1331 public boolean addAll(int index, Collection<? extends E> c) {
1332 throw new UnsupportedOperationException();
1333 }
1334
1335 @Override
1336 public void replaceAll(UnaryOperator<E> operator) {
1337 throw new UnsupportedOperationException();
1338 }
1339 @Override
1340 public void sort(Comparator<? super E> c) {
1341 throw new UnsupportedOperationException();
1342 }
1343
1344 public ListIterator<E> listIterator() {return listIterator(0);}
1345
1346 public ListIterator<E> listIterator(final int index) {
1347 return new ListIterator<E>() {
1348 private final ListIterator<? extends E> i
1349 = list.listIterator(index);
1350
1351 public boolean hasNext() {return i.hasNext();}
1352 public E next() {return i.next();}
1353 public boolean hasPrevious() {return i.hasPrevious();}
1354 public E previous() {return i.previous();}
1355 public int nextIndex() {return i.nextIndex();}
1356 public int previousIndex() {return i.previousIndex();}
1357
1358 public void remove() {
1359 throw new UnsupportedOperationException();
1360 }
1361 public void set(E e) {
1362 throw new UnsupportedOperationException();
1363 }
1364 public void add(E e) {
1365 throw new UnsupportedOperationException();
1366 }
1367
1368 @Override
1369 public void forEachRemaining(Consumer<? super E> action) {
1370 i.forEachRemaining(action);
1371 }
1372 };
1373 }
1374
1375 public List<E> subList(int fromIndex, int toIndex) {
1376 return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
1377 }
1378
1379 /**
1380 * UnmodifiableRandomAccessList instances are serialized as
1381 * UnmodifiableList instances to allow them to be deserialized
1382 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
1383 * This method inverts the transformation. As a beneficial
1384 * side-effect, it also grafts the RandomAccess marker onto
1385 * UnmodifiableList instances that were serialized in pre-1.4 JREs.
1386 *
1387 * Note: Unfortunately, UnmodifiableRandomAccessList instances
1388 * serialized in 1.4.1 and deserialized in 1.4 will become
1389 * UnmodifiableList instances, as this method was missing in 1.4.
1390 */
1391 private Object readResolve() {
1392 return (list instanceof RandomAccess
1393 ? new UnmodifiableRandomAccessList<>(list)
1394 : this);
1395 }
1396 }
1397
1398 /**
1399 * @serial include
1400 */
1401 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
1402 implements RandomAccess
1403 {
1404 UnmodifiableRandomAccessList(List<? extends E> list) {
1405 super(list);
1406 }
1407
1408 public List<E> subList(int fromIndex, int toIndex) {
1409 return new UnmodifiableRandomAccessList<>(
1410 list.subList(fromIndex, toIndex));
1411 }
1412
1413 private static final long serialVersionUID = -2542308836966382001L;
1414
1415 /**
1416 * Allows instances to be deserialized in pre-1.4 JREs (which do
1417 * not have UnmodifiableRandomAccessList). UnmodifiableList has
1418 * a readResolve method that inverts this transformation upon
1419 * deserialization.
1420 */
1421 private Object writeReplace() {
1422 return new UnmodifiableList<>(list);
1423 }
1424 }
1425
1426 /**
1427 * Returns an unmodifiable view of the specified map. This method
1428 * allows modules to provide users with "read-only" access to internal
1429 * maps. Query operations on the returned map "read through"
1430 * to the specified map, and attempts to modify the returned
1431 * map, whether direct or via its collection views, result in an
1432 * <tt>UnsupportedOperationException</tt>.<p>
1433 *
1434 * The returned map will be serializable if the specified map
1435 * is serializable.
1436 *
1437 * @param m the map for which an unmodifiable view is to be returned.
1438 * @return an unmodifiable view of the specified map.
1439 */
1440 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
1441 return new UnmodifiableMap<>(m);
1442 }
1443
1444 /**
1445 * @serial include
1446 */
1447 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
1448 private static final long serialVersionUID = -1034234728574286014L;
1449
1450 private final Map<? extends K, ? extends V> m;
1451
1452 UnmodifiableMap(Map<? extends K, ? extends V> m) {
1453 if (m==null)
1454 throw new NullPointerException();
1455 this.m = m;
1456 }
1457
1458 public int size() {return m.size();}
1459 public boolean isEmpty() {return m.isEmpty();}
1460 public boolean containsKey(Object key) {return m.containsKey(key);}
1461 public boolean containsValue(Object val) {return m.containsValue(val);}
1462 public V get(Object key) {return m.get(key);}
1463
1464 public V put(K key, V value) {
1465 throw new UnsupportedOperationException();
1466 }
1467 public V remove(Object key) {
1468 throw new UnsupportedOperationException();
1469 }
1470 public void putAll(Map<? extends K, ? extends V> m) {
1471 throw new UnsupportedOperationException();
1472 }
1473 public void clear() {
1474 throw new UnsupportedOperationException();
1475 }
1476
1477 private transient Set<K> keySet = null;
1478 private transient Set<Map.Entry<K,V>> entrySet = null;
1479 private transient Collection<V> values = null;
1480
1481 public Set<K> keySet() {
1482 if (keySet==null)
1483 keySet = unmodifiableSet(m.keySet());
1484 return keySet;
1485 }
1486
1487 public Set<Map.Entry<K,V>> entrySet() {
1488 if (entrySet==null)
1489 entrySet = new UnmodifiableEntrySet<>(m.entrySet());
1490 return entrySet;
1491 }
1492
1493 public Collection<V> values() {
1494 if (values==null)
1495 values = unmodifiableCollection(m.values());
1496 return values;
1497 }
1498
1499 public boolean equals(Object o) {return o == this || m.equals(o);}
1500 public int hashCode() {return m.hashCode();}
1501 public String toString() {return m.toString();}
1502
1503 // Override default methods in Map
1504 @Override
1505 @SuppressWarnings("unchecked")
1506 public V getOrDefault(Object k, V defaultValue) {
1507 // Safe cast as we don't change the value
1508 return ((Map<K, V>)m).getOrDefault(k, defaultValue);
1509 }
1510
1511 @Override
1512 public void forEach(BiConsumer<? super K, ? super V> action) {
1513 m.forEach(action);
1514 }
1515
1516 @Override
1517 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1518 throw new UnsupportedOperationException();
1519 }
1520
1521 @Override
1522 public V putIfAbsent(K key, V value) {
1523 throw new UnsupportedOperationException();
1524 }
1525
1526 @Override
1527 public boolean remove(Object key, Object value) {
1528 throw new UnsupportedOperationException();
1529 }
1530
1531 @Override
1532 public boolean replace(K key, V oldValue, V newValue) {
1533 throw new UnsupportedOperationException();
1534 }
1535
1536 @Override
1537 public V replace(K key, V value) {
1538 throw new UnsupportedOperationException();
1539 }
1540
1541 @Override
1542 public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
1543 throw new UnsupportedOperationException();
1544 }
1545
1546 @Override
1547 public V computeIfPresent(K key,
1548 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1549 throw new UnsupportedOperationException();
1550 }
1551
1552 @Override
1553 public V compute(K key,
1554 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1555 throw new UnsupportedOperationException();
1556 }
1557
1558 @Override
1559 public V merge(K key, V value,
1560 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1561 throw new UnsupportedOperationException();
1562 }
1563
1564 /**
1565 * We need this class in addition to UnmodifiableSet as
1566 * Map.Entries themselves permit modification of the backing Map
1567 * via their setValue operation. This class is subtle: there are
1568 * many possible attacks that must be thwarted.
1569 *
1570 * @serial include
1571 */
1572 static class UnmodifiableEntrySet<K,V>
1573 extends UnmodifiableSet<Map.Entry<K,V>> {
1574 private static final long serialVersionUID = 7854390611657943733L;
1575
1576 @SuppressWarnings({"unchecked", "rawtypes"})
1577 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
1578 // Need to cast to raw in order to work around a limitation in the type system
1579 super((Set)s);
1580 }
1581 public Iterator<Map.Entry<K,V>> iterator() {
1582 return new Iterator<Map.Entry<K,V>>() {
1583 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
1584
1585 public boolean hasNext() {
1586 return i.hasNext();
1587 }
1588 public Map.Entry<K,V> next() {
1589 return new UnmodifiableEntry<>(i.next());
1590 }
1591 public void remove() {
1592 throw new UnsupportedOperationException();
1593 }
1594 };
1595 }
1596
1597 @SuppressWarnings("unchecked")
1598 public Object[] toArray() {
1599 Object[] a = c.toArray();
1600 for (int i=0; i<a.length; i++)
1601 a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]);
1602 return a;
1603 }
1604
1605 @SuppressWarnings("unchecked")
1606 public <T> T[] toArray(T[] a) {
1607 // We don't pass a to c.toArray, to avoid window of
1608 // vulnerability wherein an unscrupulous multithreaded client
1609 // could get his hands on raw (unwrapped) Entries from c.
1610 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
1611
1612 for (int i=0; i<arr.length; i++)
1613 arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]);
1614
1615 if (arr.length > a.length)
1616 return (T[])arr;
1617
1618 System.arraycopy(arr, 0, a, 0, arr.length);
1619 if (a.length > arr.length)
1620 a[arr.length] = null;
1621 return a;
1622 }
1623
1624 /**
1625 * This method is overridden to protect the backing set against
1626 * an object with a nefarious equals function that senses
1627 * that the equality-candidate is Map.Entry and calls its
1628 * setValue method.
1629 */
1630 public boolean contains(Object o) {
1631 if (!(o instanceof Map.Entry))
1632 return false;
1633 return c.contains(
1634 new UnmodifiableEntry<>((Map.Entry<?,?>) o));
1635 }
1636
1637 /**
1638 * The next two methods are overridden to protect against
1639 * an unscrupulous List whose contains(Object o) method senses
1640 * when o is a Map.Entry, and calls o.setValue.
1641 */
1642 public boolean containsAll(Collection<?> coll) {
1643 for (Object e : coll) {
1644 if (!contains(e)) // Invokes safe contains() above
1645 return false;
1646 }
1647 return true;
1648 }
1649 public boolean equals(Object o) {
1650 if (o == this)
1651 return true;
1652
1653 if (!(o instanceof Set))
1654 return false;
1655 Set<?> s = (Set<?>) o;
1656 if (s.size() != c.size())
1657 return false;
1658 return containsAll(s); // Invokes safe containsAll() above
1659 }
1660
1661 /**
1662 * This "wrapper class" serves two purposes: it prevents
1663 * the client from modifying the backing Map, by short-circuiting
1664 * the setValue method, and it protects the backing Map against
1665 * an ill-behaved Map.Entry that attempts to modify another
1666 * Map Entry when asked to perform an equality check.
1667 */
1668 private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
1669 private Map.Entry<? extends K, ? extends V> e;
1670
1671 UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e) {this.e = e;}
1672
1673 public K getKey() {return e.getKey();}
1674 public V getValue() {return e.getValue();}
1675 public V setValue(V value) {
1676 throw new UnsupportedOperationException();
1677 }
1678 public int hashCode() {return e.hashCode();}
1679 public boolean equals(Object o) {
1680 if (this == o)
1681 return true;
1682 if (!(o instanceof Map.Entry))
1683 return false;
1684 Map.Entry<?,?> t = (Map.Entry<?,?>)o;
1685 return eq(e.getKey(), t.getKey()) &&
1686 eq(e.getValue(), t.getValue());
1687 }
1688 public String toString() {return e.toString();}
1689 }
1690 }
1691 }
1692
1693 /**
1694 * Returns an unmodifiable view of the specified sorted map. This method
1695 * allows modules to provide users with "read-only" access to internal
1696 * sorted maps. Query operations on the returned sorted map "read through"
1697 * to the specified sorted map. Attempts to modify the returned
1698 * sorted map, whether direct, via its collection views, or via its
1699 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
1700 * an <tt>UnsupportedOperationException</tt>.<p>
1701 *
1702 * The returned sorted map will be serializable if the specified sorted map
1703 * is serializable.
1704 *
1705 * @param m the sorted map for which an unmodifiable view is to be
1706 * returned.
1707 * @return an unmodifiable view of the specified sorted map.
1708 */
1709 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
1710 return new UnmodifiableSortedMap<>(m);
1711 }
1712
1713 /**
1714 * @serial include
1715 */
1716 static class UnmodifiableSortedMap<K,V>
1717 extends UnmodifiableMap<K,V>
1718 implements SortedMap<K,V>, Serializable {
1719 private static final long serialVersionUID = -8806743815996713206L;
1720
1721 private final SortedMap<K, ? extends V> sm;
1722
1723 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m;}
1724
1725 public Comparator<? super K> comparator() {return sm.comparator();}
1726
1727 public SortedMap<K,V> subMap(K fromKey, K toKey) {
1728 return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey));
1729 }
1730 public SortedMap<K,V> headMap(K toKey) {
1731 return new UnmodifiableSortedMap<>(sm.headMap(toKey));
1732 }
1733 public SortedMap<K,V> tailMap(K fromKey) {
1734 return new UnmodifiableSortedMap<>(sm.tailMap(fromKey));
1735 }
1736
1737 public K firstKey() {return sm.firstKey();}
1738 public K lastKey() {return sm.lastKey();}
1739 }
1740
1741 /**
1742 * Returns an unmodifiable view of the specified navigable map. This method
1743 * allows modules to provide users with "read-only" access to internal
1744 * navigable maps. Query operations on the returned navigable map "read
1745 * through" to the specified navigable map. Attempts to modify the returned
1746 * navigable map, whether direct, via its collection views, or via its
1747 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
1748 * an <tt>UnsupportedOperationException</tt>.<p>
1749 *
1750 * The returned navigable map will be serializable if the specified
1751 * navigable map is serializable.
1752 *
1753 * @param m the navigable map for which an unmodifiable view is to be
1754 * returned
1755 * @return an unmodifiable view of the specified navigable map
1756 * @since 1.8
1757 */
1758 public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {
1759 return new UnmodifiableNavigableMap<>(m);
1760 }
1761
1762 /**
1763 * @serial include
1764 */
1765 static class UnmodifiableNavigableMap<K,V>
1766 extends UnmodifiableSortedMap<K,V>
1767 implements NavigableMap<K,V>, Serializable {
1768 private static final long serialVersionUID = -4858195264774772197L;
1769
1770 private final NavigableMap<K, ? extends V> nm;
1771
1772 UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {super(m); nm = m;}
1773
1774 @Override
1775 public Entry<K, V> lowerEntry(K key) {
1776 return new UnmodifiableEntrySet.UnmodifiableEntry(nm.lowerEntry(key));
1777 }
1778
1779 @Override
1780 public K lowerKey(K key) {
1781 return nm.lowerKey(key);
1782 }
1783
1784 @Override
1785 public Entry<K, V> floorEntry(K key) {
1786 return new UnmodifiableEntrySet.UnmodifiableEntry(nm.floorEntry(key));
1787 }
1788
1789 @Override
1790 public K floorKey(K key) {
1791 return nm.floorKey(key);
1792 }
1793
1794 @Override
1795 public Entry<K, V> ceilingEntry(K key) {
1796 return new UnmodifiableEntrySet.UnmodifiableEntry(nm.ceilingEntry(key));
1797 }
1798
1799 @Override
1800 public K ceilingKey(K key) {
1801 return nm.ceilingKey(key);
1802 }
1803
1804 @Override
1805 public Entry<K, V> higherEntry(K key) {
1806 return new UnmodifiableEntrySet.UnmodifiableEntry(nm.higherEntry(key));
1807 }
1808
1809 @Override
1810 public K higherKey(K key) {
1811 return nm.higherKey(key);
1812 }
1813
1814 @Override
1815 public Entry<K, V> firstEntry() {
1816 return new UnmodifiableEntrySet.UnmodifiableEntry(nm.firstEntry());
1817 }
1818
1819 @Override
1820 public Entry<K, V> lastEntry() {
1821 return new UnmodifiableEntrySet.UnmodifiableEntry(nm.lastEntry());
1822 }
1823
1824 @Override
1825 public Entry<K, V> pollFirstEntry() {
1826 Entry<K,V> entry = (Entry<K,V>) nm.pollFirstEntry();
1827 return (null == entry) ? null : new UnmodifiableEntrySet.UnmodifiableEntry(entry);
1828 }
1829
1830 @Override
1831 public Entry<K, V> pollLastEntry() {
1832 Entry<K,V> entry = (Entry<K,V>) nm.pollLastEntry();
1833 return (null == entry) ? null : new UnmodifiableEntrySet.UnmodifiableEntry(entry);
1834 }
1835
1836 @Override
1837 public NavigableMap<K, V> descendingMap() {
1838 return unmodifiableNavigableMap(nm.descendingMap());
1839 }
1840
1841 @Override
1842 public NavigableSet<K> navigableKeySet() {
1843 return unmodifiableNavigableSet(nm.navigableKeySet());
1844 }
1845
1846 @Override
1847 public NavigableSet<K> descendingKeySet() {
1848 return unmodifiableNavigableSet(nm.descendingKeySet());
1849 }
1850
1851 @Override
1852 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
1853 return unmodifiableNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive));
1854 }
1855
1856 @Override
1857 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
1858 return unmodifiableNavigableMap(nm.headMap(toKey, inclusive));
1859 }
1860
1861 @Override
1862 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
1863 return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive));
1864 }
1865 }
1866
1867 // Synch Wrappers
1868
1869 /**
1870 * Returns a synchronized (thread-safe) collection backed by the specified
1871 * collection. In order to guarantee serial access, it is critical that
1872 * <strong>all</strong> access to the backing collection is accomplished
1873 * through the returned collection.<p>
1874 *
1875 * It is imperative that the user manually synchronize on the returned
1876 * collection when traversing it via {@link Iterator} or
1877 * {@link Spliterator}:
1878 * <pre>
1879 * Collection c = Collections.synchronizedCollection(myCollection);
1880 * ...
1881 * synchronized (c) {
1882 * Iterator i = c.iterator(); // Must be in the synchronized block
1883 * while (i.hasNext())
1884 * foo(i.next());
1885 * }
1886 * </pre>
1887 * Failure to follow this advice may result in non-deterministic behavior.
1888 *
1889 * <p>The returned collection does <i>not</i> pass the {@code hashCode}
1890 * and {@code equals} operations through to the backing collection, but
1891 * relies on {@code Object}'s equals and hashCode methods. This is
1892 * necessary to preserve the contracts of these operations in the case
1893 * that the backing collection is a set or a list.<p>
1894 *
1895 * The returned collection will be serializable if the specified collection
1896 * is serializable.
1897 *
1898 * @param c the collection to be "wrapped" in a synchronized collection.
1899 * @return a synchronized view of the specified collection.
1900 */
1901 public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
1902 return new SynchronizedCollection<>(c);
1903 }
1904
1905 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
1906 return new SynchronizedCollection<>(c, mutex);
1907 }
1908
1909 /**
1910 * @serial include
1911 */
1912 static class SynchronizedCollection<E> implements Collection<E>, Serializable {
1913 private static final long serialVersionUID = 3053995032091335093L;
1914
1915 final Collection<E> c; // Backing Collection
1916 final Object mutex; // Object on which to synchronize
1917
1918 SynchronizedCollection(Collection<E> c) {
1919 this.c = Objects.requireNonNull(c);
1920 mutex = this;
1921 }
1922
1923 SynchronizedCollection(Collection<E> c, Object mutex) {
1924 this.c = Objects.requireNonNull(c);
1925 this.mutex = Objects.requireNonNull(mutex);
1926 }
1927
1928 public int size() {
1929 synchronized (mutex) {return c.size();}
1930 }
1931 public boolean isEmpty() {
1932 synchronized (mutex) {return c.isEmpty();}
1933 }
1934 public boolean contains(Object o) {
1935 synchronized (mutex) {return c.contains(o);}
1936 }
1937 public Object[] toArray() {
1938 synchronized (mutex) {return c.toArray();}
1939 }
1940 public <T> T[] toArray(T[] a) {
1941 synchronized (mutex) {return c.toArray(a);}
1942 }
1943
1944 public Iterator<E> iterator() {
1945 return c.iterator(); // Must be manually synched by user!
1946 }
1947
1948 public boolean add(E e) {
1949 synchronized (mutex) {return c.add(e);}
1950 }
1951 public boolean remove(Object o) {
1952 synchronized (mutex) {return c.remove(o);}
1953 }
1954
1955 public boolean containsAll(Collection<?> coll) {
1956 synchronized (mutex) {return c.containsAll(coll);}
1957 }
1958 public boolean addAll(Collection<? extends E> coll) {
1959 synchronized (mutex) {return c.addAll(coll);}
1960 }
1961 public boolean removeAll(Collection<?> coll) {
1962 synchronized (mutex) {return c.removeAll(coll);}
1963 }
1964 public boolean retainAll(Collection<?> coll) {
1965 synchronized (mutex) {return c.retainAll(coll);}
1966 }
1967 public void clear() {
1968 synchronized (mutex) {c.clear();}
1969 }
1970 public String toString() {
1971 synchronized (mutex) {return c.toString();}
1972 }
1973 // Override default methods in Collection
1974 @Override
1975 public void forEach(Consumer<? super E> consumer) {
1976 synchronized (mutex) {c.forEach(consumer);}
1977 }
1978 @Override
1979 public boolean removeIf(Predicate<? super E> filter) {
1980 synchronized (mutex) {return c.removeIf(filter);}
1981 }
1982 @Override
1983 public Spliterator<E> spliterator() {
1984 return c.spliterator(); // Must be manually synched by user!
1985 }
1986 private void writeObject(ObjectOutputStream s) throws IOException {
1987 synchronized (mutex) {s.defaultWriteObject();}
1988 }
1989 }
1990
1991 /**
1992 * Returns a synchronized (thread-safe) set backed by the specified
1993 * set. In order to guarantee serial access, it is critical that
1994 * <strong>all</strong> access to the backing set is accomplished
1995 * through the returned set.<p>
1996 *
1997 * It is imperative that the user manually synchronize on the returned
1998 * set when iterating over it:
1999 * <pre>
2000 * Set s = Collections.synchronizedSet(new HashSet());
2001 * ...
2002 * synchronized (s) {
2003 * Iterator i = s.iterator(); // Must be in the synchronized block
2004 * while (i.hasNext())
2005 * foo(i.next());
2006 * }
2007 * </pre>
2008 * Failure to follow this advice may result in non-deterministic behavior.
2009 *
2010 * <p>The returned set will be serializable if the specified set is
2011 * serializable.
2012 *
2013 * @param s the set to be "wrapped" in a synchronized set.
2014 * @return a synchronized view of the specified set.
2015 */
2016 public static <T> Set<T> synchronizedSet(Set<T> s) {
2017 return new SynchronizedSet<>(s);
2018 }
2019
2020 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
2021 return new SynchronizedSet<>(s, mutex);
2022 }
2023
2024 /**
2025 * @serial include
2026 */
2027 static class SynchronizedSet<E>
2028 extends SynchronizedCollection<E>
2029 implements Set<E> {
2030 private static final long serialVersionUID = 487447009682186044L;
2031
2032 SynchronizedSet(Set<E> s) {
2033 super(s);
2034 }
2035 SynchronizedSet(Set<E> s, Object mutex) {
2036 super(s, mutex);
2037 }
2038
2039 public boolean equals(Object o) {
2040 if (this == o)
2041 return true;
2042 synchronized (mutex) {return c.equals(o);}
2043 }
2044 public int hashCode() {
2045 synchronized (mutex) {return c.hashCode();}
2046 }
2047 }
2048
2049 /**
2050 * Returns a synchronized (thread-safe) sorted set backed by the specified
2051 * sorted set. In order to guarantee serial access, it is critical that
2052 * <strong>all</strong> access to the backing sorted set is accomplished
2053 * through the returned sorted set (or its views).<p>
2054 *
2055 * It is imperative that the user manually synchronize on the returned
2056 * sorted set when iterating over it or any of its <tt>subSet</tt>,
2057 * <tt>headSet</tt>, or <tt>tailSet</tt> views.
2058 * <pre>
2059 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2060 * ...
2061 * synchronized (s) {
2062 * Iterator i = s.iterator(); // Must be in the synchronized block
2063 * while (i.hasNext())
2064 * foo(i.next());
2065 * }
2066 * </pre>
2067 * or:
2068 * <pre>
2069 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2070 * SortedSet s2 = s.headSet(foo);
2071 * ...
2072 * synchronized (s) { // Note: s, not s2!!!
2073 * Iterator i = s2.iterator(); // Must be in the synchronized block
2074 * while (i.hasNext())
2075 * foo(i.next());
2076 * }
2077 * </pre>
2078 * Failure to follow this advice may result in non-deterministic behavior.
2079 *
2080 * <p>The returned sorted set will be serializable if the specified
2081 * sorted set is serializable.
2082 *
2083 * @param s the sorted set to be "wrapped" in a synchronized sorted set.
2084 * @return a synchronized view of the specified sorted set.
2085 */
2086 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
2087 return new SynchronizedSortedSet<>(s);
2088 }
2089
2090 /**
2091 * @serial include
2092 */
2093 static class SynchronizedSortedSet<E>
2094 extends SynchronizedSet<E>
2095 implements SortedSet<E>
2096 {
2097 private static final long serialVersionUID = 8695801310862127406L;
2098
2099 private final SortedSet<E> ss;
2100
2101 SynchronizedSortedSet(SortedSet<E> s) {
2102 super(s);
2103 ss = s;
2104 }
2105 SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
2106 super(s, mutex);
2107 ss = s;
2108 }
2109
2110 public Comparator<? super E> comparator() {
2111 synchronized (mutex) {return ss.comparator();}
2112 }
2113
2114 public SortedSet<E> subSet(E fromElement, E toElement) {
2115 synchronized (mutex) {
2116 return new SynchronizedSortedSet<>(
2117 ss.subSet(fromElement, toElement), mutex);
2118 }
2119 }
2120 public SortedSet<E> headSet(E toElement) {
2121 synchronized (mutex) {
2122 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
2123 }
2124 }
2125 public SortedSet<E> tailSet(E fromElement) {
2126 synchronized (mutex) {
2127 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
2128 }
2129 }
2130
2131 public E first() {
2132 synchronized (mutex) {return ss.first();}
2133 }
2134 public E last() {
2135 synchronized (mutex) {return ss.last();}
2136 }
2137 }
2138
2139 /**
2140 * Returns a synchronized (thread-safe) sorted set backed by the specified
2141 * navigable set. In order to guarantee serial access, it is critical that
2142 * <strong>all</strong> access to the backing sorted set is accomplished
2143 * through the returned navigable set (or its views).<p>
2144 *
2145 * It is imperative that the user manually synchronize on the returned
2146 * navigable set when iterating over it or any of its {@code subSet},
2147 * {@code headSet}, or {@code tailSet} views.
2148 * <pre>
2149 * SortedSet s = Collections.synchronizedNavigableSet(new TreeSet());
2150 * ...
2151 * synchronized (s) {
2152 * Iterator i = s.iterator(); // Must be in the synchronized block
2153 * while (i.hasNext())
2154 * foo(i.next());
2155 * }
2156 * </pre>
2157 * or:
2158 * <pre>
2159 * SortedSet s = Collections.synchronizedNavigableSet(new TreeSet());
2160 * SortedSet s2 = s.headSet(foo);
2161 * ...
2162 * synchronized (s) { // Note: s, not s2!!!
2163 * Iterator i = s2.iterator(); // Must be in the synchronized block
2164 * while (i.hasNext())
2165 * foo(i.next());
2166 * }
2167 * </pre>
2168 * Failure to follow this advice may result in non-deterministic behavior.
2169 *
2170 * <p>The returned navigable set will be serializable if the specified
2171 * navigable set is serializable.
2172 *
2173 * @param s the navigable set to be "wrapped" in a synchronized navigable
2174 * set
2175 * @return a synchronized view of the specified navigable set
2176 * @since 1.8
2177 */
2178 public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) {
2179 return new SynchronizedNavigableSet<>(s);
2180 }
2181
2182 /**
2183 * @serial include
2184 */
2185 static class SynchronizedNavigableSet<E>
2186 extends SynchronizedSortedSet<E>
2187 implements NavigableSet<E>
2188 {
2189 private static final long serialVersionUID = -5505529816273629798L;
2190
2191 private final NavigableSet<E> ns;
2192
2193 SynchronizedNavigableSet(NavigableSet<E> s) {
2194 super(s);
2195 ns = s;
2196 }
2197
2198 SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) {
2199 super(s, mutex);
2200 ns = s;
2201 }
2202 public E lower(E e) { synchronized (mutex) {return ns.lower(e);} }
2203 public E floor(E e) { synchronized (mutex) {return ns.floor(e);} }
2204 public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} }
2205 public E higher(E e) { synchronized (mutex) {return ns.higher(e);} }
2206 public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} }
2207 public E pollLast() { synchronized (mutex) {return ns.pollLast();} }
2208
2209 public NavigableSet<E> descendingSet() {
2210 synchronized (mutex) {
2211 return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex);
2212 }
2213 }
2214
2215 public Iterator<E> descendingIterator()
2216 { synchronized (mutex) { return descendingSet().iterator(); } }
2217
2218 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
2219 synchronized (mutex) {
2220 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex);
2221 }
2222 }
2223
2224 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
2225 synchronized (mutex) {
2226 return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex);
2227 }
2228 }
2229
2230 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
2231 synchronized (mutex) {
2232 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive));
2233 }
2234 }
2235 }
2236
2237 /**
2238 * Returns a synchronized (thread-safe) list backed by the specified
2239 * list. In order to guarantee serial access, it is critical that
2240 * <strong>all</strong> access to the backing list is accomplished
2241 * through the returned list.<p>
2242 *
2243 * It is imperative that the user manually synchronize on the returned
2244 * list when iterating over it:
2245 * <pre>
2246 * List list = Collections.synchronizedList(new ArrayList());
2247 * ...
2248 * synchronized (list) {
2249 * Iterator i = list.iterator(); // Must be in synchronized block
2250 * while (i.hasNext())
2251 * foo(i.next());
2252 * }
2253 * </pre>
2254 * Failure to follow this advice may result in non-deterministic behavior.
2255 *
2256 * <p>The returned list will be serializable if the specified list is
2257 * serializable.
2258 *
2259 * @param list the list to be "wrapped" in a synchronized list.
2260 * @return a synchronized view of the specified list.
2261 */
2262 public static <T> List<T> synchronizedList(List<T> list) {
2263 return (list instanceof RandomAccess ?
2264 new SynchronizedRandomAccessList<>(list) :
2265 new SynchronizedList<>(list));
2266 }
2267
2268 static <T> List<T> synchronizedList(List<T> list, Object mutex) {
2269 return (list instanceof RandomAccess ?
2270 new SynchronizedRandomAccessList<>(list, mutex) :
2271 new SynchronizedList<>(list, mutex));
2272 }
2273
2274 /**
2275 * @serial include
2276 */
2277 static class SynchronizedList<E>
2278 extends SynchronizedCollection<E>
2279 implements List<E> {
2280 private static final long serialVersionUID = -7754090372962971524L;
2281
2282 final List<E> list;
2283
2284 SynchronizedList(List<E> list) {
2285 super(list);
2286 this.list = list;
2287 }
2288 SynchronizedList(List<E> list, Object mutex) {
2289 super(list, mutex);
2290 this.list = list;
2291 }
2292
2293 public boolean equals(Object o) {
2294 if (this == o)
2295 return true;
2296 synchronized (mutex) {return list.equals(o);}
2297 }
2298 public int hashCode() {
2299 synchronized (mutex) {return list.hashCode();}
2300 }
2301
2302 public E get(int index) {
2303 synchronized (mutex) {return list.get(index);}
2304 }
2305 public E set(int index, E element) {
2306 synchronized (mutex) {return list.set(index, element);}
2307 }
2308 public void add(int index, E element) {
2309 synchronized (mutex) {list.add(index, element);}
2310 }
2311 public E remove(int index) {
2312 synchronized (mutex) {return list.remove(index);}
2313 }
2314
2315 public int indexOf(Object o) {
2316 synchronized (mutex) {return list.indexOf(o);}
2317 }
2318 public int lastIndexOf(Object o) {
2319 synchronized (mutex) {return list.lastIndexOf(o);}
2320 }
2321
2322 public boolean addAll(int index, Collection<? extends E> c) {
2323 synchronized (mutex) {return list.addAll(index, c);}
2324 }
2325
2326 public ListIterator<E> listIterator() {
2327 return list.listIterator(); // Must be manually synched by user
2328 }
2329
2330 public ListIterator<E> listIterator(int index) {
2331 return list.listIterator(index); // Must be manually synched by user
2332 }
2333
2334 public List<E> subList(int fromIndex, int toIndex) {
2335 synchronized (mutex) {
2336 return new SynchronizedList<>(list.subList(fromIndex, toIndex),
2337 mutex);
2338 }
2339 }
2340
2341 @Override
2342 public void replaceAll(UnaryOperator<E> operator) {
2343 synchronized (mutex) {list.replaceAll(operator);}
2344 }
2345 @Override
2346 public void sort(Comparator<? super E> c) {
2347 synchronized (mutex) {list.sort(c);}
2348 }
2349
2350 /**
2351 * SynchronizedRandomAccessList instances are serialized as
2352 * SynchronizedList instances to allow them to be deserialized
2353 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
2354 * This method inverts the transformation. As a beneficial
2355 * side-effect, it also grafts the RandomAccess marker onto
2356 * SynchronizedList instances that were serialized in pre-1.4 JREs.
2357 *
2358 * Note: Unfortunately, SynchronizedRandomAccessList instances
2359 * serialized in 1.4.1 and deserialized in 1.4 will become
2360 * SynchronizedList instances, as this method was missing in 1.4.
2361 */
2362 private Object readResolve() {
2363 return (list instanceof RandomAccess
2364 ? new SynchronizedRandomAccessList<>(list)
2365 : this);
2366 }
2367 }
2368
2369 /**
2370 * @serial include
2371 */
2372 static class SynchronizedRandomAccessList<E>
2373 extends SynchronizedList<E>
2374 implements RandomAccess {
2375
2376 SynchronizedRandomAccessList(List<E> list) {
2377 super(list);
2378 }
2379
2380 SynchronizedRandomAccessList(List<E> list, Object mutex) {
2381 super(list, mutex);
2382 }
2383
2384 public List<E> subList(int fromIndex, int toIndex) {
2385 synchronized (mutex) {
2386 return new SynchronizedRandomAccessList<>(
2387 list.subList(fromIndex, toIndex), mutex);
2388 }
2389 }
2390
2391 private static final long serialVersionUID = 1530674583602358482L;
2392
2393 /**
2394 * Allows instances to be deserialized in pre-1.4 JREs (which do
2395 * not have SynchronizedRandomAccessList). SynchronizedList has
2396 * a readResolve method that inverts this transformation upon
2397 * deserialization.
2398 */
2399 private Object writeReplace() {
2400 return new SynchronizedList<>(list);
2401 }
2402 }
2403
2404 /**
2405 * Returns a synchronized (thread-safe) map backed by the specified
2406 * map. In order to guarantee serial access, it is critical that
2407 * <strong>all</strong> access to the backing map is accomplished
2408 * through the returned map.<p>
2409 *
2410 * It is imperative that the user manually synchronize on the returned
2411 * map when iterating over any of its collection views:
2412 * <pre>
2413 * Map m = Collections.synchronizedMap(new HashMap());
2414 * ...
2415 * Set s = m.keySet(); // Needn't be in synchronized block
2416 * ...
2417 * synchronized (m) { // Synchronizing on m, not s!
2418 * Iterator i = s.iterator(); // Must be in synchronized block
2419 * while (i.hasNext())
2420 * foo(i.next());
2421 * }
2422 * </pre>
2423 * Failure to follow this advice may result in non-deterministic behavior.
2424 *
2425 * <p>The returned map will be serializable if the specified map is
2426 * serializable.
2427 *
2428 * @param m the map to be "wrapped" in a synchronized map.
2429 * @return a synchronized view of the specified map.
2430 */
2431 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
2432 return new SynchronizedMap<>(m);
2433 }
2434
2435 /**
2436 * @serial include
2437 */
2438 private static class SynchronizedMap<K,V>
2439 implements Map<K,V>, Serializable {
2440 private static final long serialVersionUID = 1978198479659022715L;
2441
2442 private final Map<K,V> m; // Backing Map
2443 final Object mutex; // Object on which to synchronize
2444
2445 SynchronizedMap(Map<K,V> m) {
2446 this.m = Objects.requireNonNull(m);
2447 mutex = this;
2448 }
2449
2450 SynchronizedMap(Map<K,V> m, Object mutex) {
2451 this.m = m;
2452 this.mutex = mutex;
2453 }
2454
2455 public int size() {
2456 synchronized (mutex) {return m.size();}
2457 }
2458 public boolean isEmpty() {
2459 synchronized (mutex) {return m.isEmpty();}
2460 }
2461 public boolean containsKey(Object key) {
2462 synchronized (mutex) {return m.containsKey(key);}
2463 }
2464 public boolean containsValue(Object value) {
2465 synchronized (mutex) {return m.containsValue(value);}
2466 }
2467 public V get(Object key) {
2468 synchronized (mutex) {return m.get(key);}
2469 }
2470
2471 public V put(K key, V value) {
2472 synchronized (mutex) {return m.put(key, value);}
2473 }
2474 public V remove(Object key) {
2475 synchronized (mutex) {return m.remove(key);}
2476 }
2477 public void putAll(Map<? extends K, ? extends V> map) {
2478 synchronized (mutex) {m.putAll(map);}
2479 }
2480 public void clear() {
2481 synchronized (mutex) {m.clear();}
2482 }
2483
2484 private transient Set<K> keySet = null;
2485 private transient Set<Map.Entry<K,V>> entrySet = null;
2486 private transient Collection<V> values = null;
2487
2488 public Set<K> keySet() {
2489 synchronized (mutex) {
2490 if (keySet==null)
2491 keySet = new SynchronizedSet<>(m.keySet(), mutex);
2492 return keySet;
2493 }
2494 }
2495
2496 public Set<Map.Entry<K,V>> entrySet() {
2497 synchronized (mutex) {
2498 if (entrySet==null)
2499 entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
2500 return entrySet;
2501 }
2502 }
2503
2504 public Collection<V> values() {
2505 synchronized (mutex) {
2506 if (values==null)
2507 values = new SynchronizedCollection<>(m.values(), mutex);
2508 return values;
2509 }
2510 }
2511
2512 public boolean equals(Object o) {
2513 if (this == o)
2514 return true;
2515 synchronized (mutex) {return m.equals(o);}
2516 }
2517 public int hashCode() {
2518 synchronized (mutex) {return m.hashCode();}
2519 }
2520 public String toString() {
2521 synchronized (mutex) {return m.toString();}
2522 }
2523
2524 // Override default methods in Map
2525 @Override
2526 public V getOrDefault(Object k, V defaultValue) {
2527 synchronized (mutex) {return m.getOrDefault(k, defaultValue);}
2528 }
2529 @Override
2530 public void forEach(BiConsumer<? super K, ? super V> action) {
2531 synchronized (mutex) {m.forEach(action);}
2532 }
2533 @Override
2534 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
2535 synchronized (mutex) {m.replaceAll(function);}
2536 }
2537 @Override
2538 public V putIfAbsent(K key, V value) {
2539 synchronized (mutex) {return m.putIfAbsent(key, value);}
2540 }
2541 @Override
2542 public boolean remove(Object key, Object value) {
2543 synchronized (mutex) {return m.remove(key, value);}
2544 }
2545 @Override
2546 public boolean replace(K key, V oldValue, V newValue) {
2547 synchronized (mutex) {return m.replace(key, oldValue, newValue);}
2548 }
2549 @Override
2550 public V replace(K key, V value) {
2551 synchronized (mutex) {return m.replace(key, value);}
2552 }
2553 @Override
2554 public V computeIfAbsent(K key,
2555 Function<? super K, ? extends V> mappingFunction) {
2556 synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);}
2557 }
2558 @Override
2559 public V computeIfPresent(K key,
2560 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2561 synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);}
2562 }
2563 @Override
2564 public V compute(K key,
2565 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2566 synchronized (mutex) {return m.compute(key, remappingFunction);}
2567 }
2568 @Override
2569 public V merge(K key, V value,
2570 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
2571 synchronized (mutex) {return m.merge(key, value, remappingFunction);}
2572 }
2573
2574 private void writeObject(ObjectOutputStream s) throws IOException {
2575 synchronized (mutex) {s.defaultWriteObject();}
2576 }
2577 }
2578
2579 /**
2580 * Returns a synchronized (thread-safe) sorted map backed by the specified
2581 * sorted map. In order to guarantee serial access, it is critical that
2582 * <strong>all</strong> access to the backing sorted map is accomplished
2583 * through the returned sorted map (or its views).<p>
2584 *
2585 * It is imperative that the user manually synchronize on the returned
2586 * sorted map when iterating over any of its collection views, or the
2587 * collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or
2588 * <tt>tailMap</tt> views.
2589 * <pre>
2590 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2591 * ...
2592 * Set s = m.keySet(); // Needn't be in synchronized block
2593 * ...
2594 * synchronized (m) { // Synchronizing on m, not s!
2595 * Iterator i = s.iterator(); // Must be in synchronized block
2596 * while (i.hasNext())
2597 * foo(i.next());
2598 * }
2599 * </pre>
2600 * or:
2601 * <pre>
2602 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2603 * SortedMap m2 = m.subMap(foo, bar);
2604 * ...
2605 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2606 * ...
2607 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2608 * Iterator i = s.iterator(); // Must be in synchronized block
2609 * while (i.hasNext())
2610 * foo(i.next());
2611 * }
2612 * </pre>
2613 * Failure to follow this advice may result in non-deterministic behavior.
2614 *
2615 * <p>The returned sorted map will be serializable if the specified
2616 * sorted map is serializable.
2617 *
2618 * @param m the sorted map to be "wrapped" in a synchronized sorted map.
2619 * @return a synchronized view of the specified sorted map.
2620 */
2621 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
2622 return new SynchronizedSortedMap<>(m);
2623 }
2624
2625 /**
2626 * @serial include
2627 */
2628 static class SynchronizedSortedMap<K,V>
2629 extends SynchronizedMap<K,V>
2630 implements SortedMap<K,V>
2631 {
2632 private static final long serialVersionUID = -8798146769416483793L;
2633
2634 private final SortedMap<K,V> sm;
2635
2636 SynchronizedSortedMap(SortedMap<K,V> m) {
2637 super(m);
2638 sm = m;
2639 }
2640 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
2641 super(m, mutex);
2642 sm = m;
2643 }
2644
2645 public Comparator<? super K> comparator() {
2646 synchronized (mutex) {return sm.comparator();}
2647 }
2648
2649 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2650 synchronized (mutex) {
2651 return new SynchronizedSortedMap<>(
2652 sm.subMap(fromKey, toKey), mutex);
2653 }
2654 }
2655 public SortedMap<K,V> headMap(K toKey) {
2656 synchronized (mutex) {
2657 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
2658 }
2659 }
2660 public SortedMap<K,V> tailMap(K fromKey) {
2661 synchronized (mutex) {
2662 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
2663 }
2664 }
2665
2666 public K firstKey() {
2667 synchronized (mutex) {return sm.firstKey();}
2668 }
2669 public K lastKey() {
2670 synchronized (mutex) {return sm.lastKey();}
2671 }
2672 }
2673
2674 /**
2675 * Returns a synchronized (thread-safe) navigable map backed by the
2676 * specified navigable map. In order to guarantee serial access, it is
2677 * critical that <strong>all</strong> access to the backing navigable map is
2678 * accomplished through the returned navigable map (or its views).<p>
2679 *
2680 * It is imperative that the user manually synchronize on the returned
2681 * navigable map when iterating over any of its collection views, or the
2682 * collections views of any of its {@code subMap}, {@code headMap} or
2683 * {@code tailMap} views.
2684 * <pre>
2685 * SortedMap m = Collections.synchronizedNavigableMap(new TreeMap());
2686 * ...
2687 * Set s = m.keySet(); // Needn't be in synchronized block
2688 * ...
2689 * synchronized (m) { // Synchronizing on m, not s!
2690 * Iterator i = s.iterator(); // Must be in synchronized block
2691 * while (i.hasNext())
2692 * foo(i.next());
2693 * }
2694 * </pre>
2695 * or:
2696 * <pre>
2697 * SortedMap m = Collections.synchronizedNavigableMap(new TreeMap());
2698 * SortedMap m2 = m.subMap(foo, bar);
2699 * ...
2700 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2701 * ...
2702 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2703 * Iterator i = s.iterator(); // Must be in synchronized block
2704 * while (i.hasNext())
2705 * foo(i.next());
2706 * }
2707 * </pre>
2708 * Failure to follow this advice may result in non-deterministic behavior.
2709 *
2710 * <p>The returned navigable map will be serializable if the specified
2711 * navigable map is serializable.
2712 *
2713 * @param m the navigable map to be "wrapped" in a synchronized navigable
2714 * map
2715 * @return a synchronized view of the specified navigable map.
2716 * @since 1.8
2717 */
2718 public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) {
2719 return new SynchronizedNavigableMap<>(m);
2720 }
2721
2722 /**
2723 * A synchronized NavigableMap.
2724 *
2725 * @serial include
2726 */
2727 static class SynchronizedNavigableMap<K,V>
2728 extends SynchronizedSortedMap<K,V>
2729 implements NavigableMap<K,V>
2730 {
2731 private static final long serialVersionUID = 699392247599746807L;
2732
2733 private final NavigableMap<K,V> nm;
2734
2735 SynchronizedNavigableMap(NavigableMap<K,V> m) {
2736 super(m);
2737 nm = m;
2738 }
2739 SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) {
2740 super(m, mutex);
2741 nm = m;
2742 }
2743
2744 public Entry<K, V> lowerEntry(K key)
2745 { synchronized (mutex) { return nm.lowerEntry(key); } }
2746 public K lowerKey(K key)
2747 { synchronized (mutex) { return nm.lowerKey(key); } }
2748 public Entry<K, V> floorEntry(K key)
2749 { synchronized (mutex) { return nm.floorEntry(key); } }
2750 public K floorKey(K key)
2751 { synchronized (mutex) { return nm.floorKey(key); } }
2752 public Entry<K, V> ceilingEntry(K key)
2753 { synchronized (mutex) { return nm.ceilingEntry(key); } }
2754 public K ceilingKey(K key)
2755 { synchronized (mutex) { return nm.ceilingKey(key); } }
2756
2757 @Override
2758 public Entry<K, V> higherEntry(K key) {
2759 synchronized (mutex) { return nm.higherEntry(key); }
2760 }
2761
2762 @Override
2763 public K higherKey(K key) {
2764 synchronized (mutex) { return nm.higherKey(key); }
2765 }
2766
2767 @Override
2768 public Entry<K, V> firstEntry() {
2769 synchronized (mutex) { return nm.firstEntry(); }
2770 }
2771
2772 @Override
2773 public Entry<K, V> lastEntry() {
2774 synchronized (mutex) { return nm.lastEntry(); }
2775 }
2776
2777 @Override
2778 public Entry<K, V> pollFirstEntry() {
2779 synchronized (mutex) {
2780 return nm.pollFirstEntry();
2781 }
2782 }
2783
2784 @Override
2785 public Entry<K, V> pollLastEntry() {
2786 synchronized (mutex) {
2787 return nm.pollLastEntry();
2788 }
2789 }
2790
2791 @Override
2792 public NavigableMap<K, V> descendingMap() {
2793 synchronized (mutex) {
2794 return (NavigableMap<K,V>)
2795 new SynchronizedNavigableMap(nm.descendingMap(), mutex);
2796 }
2797 }
2798
2799 @Override
2800 public NavigableSet<K> navigableKeySet() {
2801 synchronized (mutex) {
2802 return new SynchronizedNavigableSet(nm.navigableKeySet(), mutex);
2803 }
2804 }
2805
2806 @Override
2807 public NavigableSet<K> descendingKeySet() {
2808 synchronized (mutex) {
2809 return new SynchronizedNavigableSet(nm.descendingKeySet(), mutex);
2810 }
2811 }
2812
2813 @Override
2814 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
2815 synchronized (mutex) {
2816 return (NavigableMap<K,V>) new SynchronizedNavigableMap(
2817 nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex);
2818 }
2819 }
2820
2821 @Override
2822 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
2823 synchronized (mutex) {
2824 return (NavigableMap<K,V>) new SynchronizedNavigableMap(
2825 nm.headMap(toKey, inclusive), mutex);
2826 }
2827 }
2828
2829 @Override
2830 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
2831 synchronized (mutex) {
2832 return (NavigableMap<K,V>) new SynchronizedNavigableMap(
2833 nm.tailMap(fromKey, inclusive), mutex);
2834 }
2835 }
2836 }
2837
2838 // Dynamically typesafe collection wrappers
2839
2840 /**
2841 * Returns a dynamically typesafe view of the specified collection.
2842 * Any attempt to insert an element of the wrong type will result in an
2843 * immediate {@link ClassCastException}. Assuming a collection
2844 * contains no incorrectly typed elements prior to the time a
2845 * dynamically typesafe view is generated, and that all subsequent
2846 * access to the collection takes place through the view, it is
2847 * <i>guaranteed</i> that the collection cannot contain an incorrectly
2848 * typed element.
2849 *
2850 * <p>The generics mechanism in the language provides compile-time
2851 * (static) type checking, but it is possible to defeat this mechanism
2852 * with unchecked casts. Usually this is not a problem, as the compiler
2853 * issues warnings on all such unchecked operations. There are, however,
2854 * times when static type checking alone is not sufficient. For example,
2855 * suppose a collection is passed to a third-party library and it is
2856 * imperative that the library code not corrupt the collection by
2857 * inserting an element of the wrong type.
2858 *
2859 * <p>Another use of dynamically typesafe views is debugging. Suppose a
2860 * program fails with a {@code ClassCastException}, indicating that an
2861 * incorrectly typed element was put into a parameterized collection.
2862 * Unfortunately, the exception can occur at any time after the erroneous
2863 * element is inserted, so it typically provides little or no information
2864 * as to the real source of the problem. If the problem is reproducible,
2865 * one can quickly determine its source by temporarily modifying the
2866 * program to wrap the collection with a dynamically typesafe view.
2867 * For example, this declaration:
2868 * <pre> {@code
2869 * Collection<String> c = new HashSet<>();
2870 * }</pre>
2871 * may be replaced temporarily by this one:
2872 * <pre> {@code
2873 * Collection<String> c = Collections.checkedCollection(
2874 * new HashSet<>(), String.class);
2875 * }</pre>
2876 * Running the program again will cause it to fail at the point where
2877 * an incorrectly typed element is inserted into the collection, clearly
2878 * identifying the source of the problem. Once the problem is fixed, the
2879 * modified declaration may be reverted back to the original.
2880 *
2881 * <p>The returned collection does <i>not</i> pass the hashCode and equals
2882 * operations through to the backing collection, but relies on
2883 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
2884 * is necessary to preserve the contracts of these operations in the case
2885 * that the backing collection is a set or a list.
2886 *
2887 * <p>The returned collection will be serializable if the specified
2888 * collection is serializable.
2889 *
2890 * <p>Since {@code null} is considered to be a value of any reference
2891 * type, the returned collection permits insertion of null elements
2892 * whenever the backing collection does.
2893 *
2894 * @param c the collection for which a dynamically typesafe view is to be
2895 * returned
2896 * @param type the type of element that {@code c} is permitted to hold
2897 * @return a dynamically typesafe view of the specified collection
2898 * @since 1.5
2899 */
2900 public static <E> Collection<E> checkedCollection(Collection<E> c,
2901 Class<E> type) {
2902 return new CheckedCollection<>(c, type);
2903 }
2904
2905 @SuppressWarnings("unchecked")
2906 static <T> T[] zeroLengthArray(Class<T> type) {
2907 return (T[]) Array.newInstance(type, 0);
2908 }
2909
2910 /**
2911 * @serial include
2912 */
2913 static class CheckedCollection<E> implements Collection<E>, Serializable {
2914 private static final long serialVersionUID = 1578914078182001775L;
2915
2916 final Collection<E> c;
2917 final Class<E> type;
2918
2919 void typeCheck(Object o) {
2920 if (o != null && !type.isInstance(o))
2921 throw new ClassCastException(badElementMsg(o));
2922 }
2923
2924 private String badElementMsg(Object o) {
2925 return "Attempt to insert " + o.getClass() +
2926 " element into collection with element type " + type;
2927 }
2928
2929 CheckedCollection(Collection<E> c, Class<E> type) {
2930 if (c==null || type == null)
2931 throw new NullPointerException();
2932 this.c = c;
2933 this.type = type;
2934 }
2935
2936 public int size() { return c.size(); }
2937 public boolean isEmpty() { return c.isEmpty(); }
2938 public boolean contains(Object o) { return c.contains(o); }
2939 public Object[] toArray() { return c.toArray(); }
2940 public <T> T[] toArray(T[] a) { return c.toArray(a); }
2941 public String toString() { return c.toString(); }
2942 public boolean remove(Object o) { return c.remove(o); }
2943 public void clear() { c.clear(); }
2944
2945 public boolean containsAll(Collection<?> coll) {
2946 return c.containsAll(coll);
2947 }
2948 public boolean removeAll(Collection<?> coll) {
2949 return c.removeAll(coll);
2950 }
2951 public boolean retainAll(Collection<?> coll) {
2952 return c.retainAll(coll);
2953 }
2954
2955 public Iterator<E> iterator() {
2956 // JDK-6363904 - unwrapped iterator could be typecast to
2957 // ListIterator with unsafe set()
2958 final Iterator<E> it = c.iterator();
2959 return new Iterator<E>() {
2960 public boolean hasNext() { return it.hasNext(); }
2961 public E next() { return it.next(); }
2962 public void remove() { it.remove(); }};
2963 }
2964
2965 public boolean add(E e) {
2966 typeCheck(e);
2967 return c.add(e);
2968 }
2969
2970 private E[] zeroLengthElementArray = null; // Lazily initialized
2971
2972 private E[] zeroLengthElementArray() {
2973 return zeroLengthElementArray != null ? zeroLengthElementArray :
2974 (zeroLengthElementArray = zeroLengthArray(type));
2975 }
2976
2977 @SuppressWarnings("unchecked")
2978 Collection<E> checkedCopyOf(Collection<? extends E> coll) {
2979 Object[] a = null;
2980 try {
2981 E[] z = zeroLengthElementArray();
2982 a = coll.toArray(z);
2983 // Defend against coll violating the toArray contract
2984 if (a.getClass() != z.getClass())
2985 a = Arrays.copyOf(a, a.length, z.getClass());
2986 } catch (ArrayStoreException ignore) {
2987 // To get better and consistent diagnostics,
2988 // we call typeCheck explicitly on each element.
2989 // We call clone() to defend against coll retaining a
2990 // reference to the returned array and storing a bad
2991 // element into it after it has been type checked.
2992 a = coll.toArray().clone();
2993 for (Object o : a)
2994 typeCheck(o);
2995 }
2996 // A slight abuse of the type system, but safe here.
2997 return (Collection<E>) Arrays.asList(a);
2998 }
2999
3000 public boolean addAll(Collection<? extends E> coll) {
3001 // Doing things this way insulates us from concurrent changes
3002 // in the contents of coll and provides all-or-nothing
3003 // semantics (which we wouldn't get if we type-checked each
3004 // element as we added it)
3005 return c.addAll(checkedCopyOf(coll));
3006 }
3007
3008 // Override default methods in Collection
3009 @Override
3010 public void forEach(Consumer<? super E> action) {c.forEach(action);}
3011 @Override
3012 public boolean removeIf(Predicate<? super E> filter) {
3013 return c.removeIf(filter);
3014 }
3015 @Override
3016 public Spliterator<E> spliterator() {return c.spliterator();}
3017 }
3018
3019 /**
3020 * Returns a dynamically typesafe view of the specified queue.
3021 * Any attempt to insert an element of the wrong type will result in
3022 * an immediate {@link ClassCastException}. Assuming a queue contains
3023 * no incorrectly typed elements prior to the time a dynamically typesafe
3024 * view is generated, and that all subsequent access to the queue
3025 * takes place through the view, it is <i>guaranteed</i> that the
3026 * queue cannot contain an incorrectly typed element.
3027 *
3028 * <p>A discussion of the use of dynamically typesafe views may be
3029 * found in the documentation for the {@link #checkedCollection
3030 * checkedCollection} method.
3031 *
3032 * <p>The returned queue will be serializable if the specified queue
3033 * is serializable.
3034 *
3035 * <p>Since {@code null} is considered to be a value of any reference
3036 * type, the returned queue permits insertion of {@code null} elements
3037 * whenever the backing queue does.
3038 *
3039 * @param queue the queue for which a dynamically typesafe view is to be
3040 * returned
3041 * @param type the type of element that {@code queue} is permitted to hold
3042 * @return a dynamically typesafe view of the specified queue
3043 * @since 1.8
3044 */
3045 public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) {
3046 return new CheckedQueue<>(queue, type);
3047 }
3048
3049 /**
3050 * @serial include
3051 */
3052 static class CheckedQueue<E>
3053 extends CheckedCollection<E>
3054 implements Queue<E>, Serializable
3055 {
3056 private static final long serialVersionUID = 1433151992604707767L;
3057 final Queue<E> queue;
3058
3059 CheckedQueue(Queue<E> queue, Class<E> elementType) {
3060 super(queue, elementType);
3061 this.queue = queue;
3062 }
3063
3064 public E element() {return queue.element();}
3065 public boolean equals(Object o) {return o == this || c.equals(o);}
3066 public int hashCode() {return c.hashCode();}
3067 public E peek() {return queue.peek();}
3068 public E poll() {return queue.poll();}
3069 public E remove() {return queue.remove();}
3070
3071 public boolean offer(E e) {
3072 typeCheck(e);
3073 return add(e);
3074 }
3075 }
3076
3077 /**
3078 * Returns a dynamically typesafe view of the specified set.
3079 * Any attempt to insert an element of the wrong type will result in
3080 * an immediate {@link ClassCastException}. Assuming a set contains
3081 * no incorrectly typed elements prior to the time a dynamically typesafe
3082 * view is generated, and that all subsequent access to the set
3083 * takes place through the view, it is <i>guaranteed</i> that the
3084 * set cannot contain an incorrectly typed element.
3085 *
3086 * <p>A discussion of the use of dynamically typesafe views may be
3087 * found in the documentation for the {@link #checkedCollection
3088 * checkedCollection} method.
3089 *
3090 * <p>The returned set will be serializable if the specified set is
3091 * serializable.
3092 *
3093 * <p>Since {@code null} is considered to be a value of any reference
3094 * type, the returned set permits insertion of null elements whenever
3095 * the backing set does.
3096 *
3097 * @param s the set for which a dynamically typesafe view is to be
3098 * returned
3099 * @param type the type of element that {@code s} is permitted to hold
3100 * @return a dynamically typesafe view of the specified set
3101 * @since 1.5
3102 */
3103 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
3104 return new CheckedSet<>(s, type);
3105 }
3106
3107 /**
3108 * @serial include
3109 */
3110 static class CheckedSet<E> extends CheckedCollection<E>
3111 implements Set<E>, Serializable
3112 {
3113 private static final long serialVersionUID = 4694047833775013803L;
3114
3115 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
3116
3117 public boolean equals(Object o) { return o == this || c.equals(o); }
3118 public int hashCode() { return c.hashCode(); }
3119 }
3120
3121 /**
3122 * Returns a dynamically typesafe view of the specified sorted set.
3123 * Any attempt to insert an element of the wrong type will result in an
3124 * immediate {@link ClassCastException}. Assuming a sorted set
3125 * contains no incorrectly typed elements prior to the time a
3126 * dynamically typesafe view is generated, and that all subsequent
3127 * access to the sorted set takes place through the view, it is
3128 * <i>guaranteed</i> that the sorted set cannot contain an incorrectly
3129 * typed element.
3130 *
3131 * <p>A discussion of the use of dynamically typesafe views may be
3132 * found in the documentation for the {@link #checkedCollection
3133 * checkedCollection} method.
3134 *
3135 * <p>The returned sorted set will be serializable if the specified sorted
3136 * set is serializable.
3137 *
3138 * <p>Since {@code null} is considered to be a value of any reference
3139 * type, the returned sorted set permits insertion of null elements
3140 * whenever the backing sorted set does.
3141 *
3142 * @param s the sorted set for which a dynamically typesafe view is to be
3143 * returned
3144 * @param type the type of element that {@code s} is permitted to hold
3145 * @return a dynamically typesafe view of the specified sorted set
3146 * @since 1.5
3147 */
3148 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
3149 Class<E> type) {
3150 return new CheckedSortedSet<>(s, type);
3151 }
3152
3153 /**
3154 * @serial include
3155 */
3156 static class CheckedSortedSet<E> extends CheckedSet<E>
3157 implements SortedSet<E>, Serializable
3158 {
3159 private static final long serialVersionUID = 1599911165492914959L;
3160
3161 private final SortedSet<E> ss;
3162
3163 CheckedSortedSet(SortedSet<E> s, Class<E> type) {
3164 super(s, type);
3165 ss = s;
3166 }
3167
3168 public Comparator<? super E> comparator() { return ss.comparator(); }
3169 public E first() { return ss.first(); }
3170 public E last() { return ss.last(); }
3171
3172 public SortedSet<E> subSet(E fromElement, E toElement) {
3173 return checkedSortedSet(ss.subSet(fromElement,toElement), type);
3174 }
3175 public SortedSet<E> headSet(E toElement) {
3176 return checkedSortedSet(ss.headSet(toElement), type);
3177 }
3178 public SortedSet<E> tailSet(E fromElement) {
3179 return checkedSortedSet(ss.tailSet(fromElement), type);
3180 }
3181 }
3182
3183 /**
3184 * Returns a dynamically typesafe view of the specified navigable set.
3185 * Any attempt to insert an element of the wrong type will result in an
3186 * immediate {@link ClassCastException}. Assuming a navigable set
3187 * contains no incorrectly typed elements prior to the time a
3188 * dynamically typesafe view is generated, and that all subsequent
3189 * access to the navigable set takes place through the view, it is
3190 * <em>guaranteed</em> that the navigable set cannot contain an incorrectly
3191 * typed element.
3192 *
3193 * <p>A discussion of the use of dynamically typesafe views may be
3194 * found in the documentation for the {@link #checkedCollection
3195 * checkedCollection} method.
3196 *
3197 * <p>The returned navigable set will be serializable if the specified
3198 * navigable set is serializable.
3199 *
3200 * <p>Since {@code null} is considered to be a value of any reference
3201 * type, the returned navigable set permits insertion of null elements
3202 * whenever the backing sorted set does.
3203 *
3204 * @param s the navigable set for which a dynamically typesafe view is to be
3205 * returned
3206 * @param type the type of element that {@code s} is permitted to hold
3207 * @return a dynamically typesafe view of the specified navigable set
3208 * @since 1.8
3209 */
3210 public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s,
3211 Class<E> type) {
3212 return new CheckedNavigableSet<>(s, type);
3213 }
3214
3215 /**
3216 * @serial include
3217 */
3218 static class CheckedNavigableSet<E> extends CheckedSortedSet<E>
3219 implements NavigableSet<E>, Serializable
3220 {
3221 private static final long serialVersionUID = -5429120189805438922L;
3222
3223 private final NavigableSet<E> ns;
3224
3225 CheckedNavigableSet(NavigableSet<E> s, Class<E> type) {
3226 super(s, type);
3227 ns = s;
3228 }
3229
3230 public E lower(E e) { return ns.lower(e); }
3231 public E floor(E e) { return ns.floor(e); }
3232 public E ceiling(E e) { return ns.ceiling(e); }
3233 public E higher(E e) { return ns.higher(e); }
3234 public E pollFirst() { return ns.pollFirst(); }
3235 public E pollLast() {return ns.pollLast(); }
3236 public NavigableSet<E> descendingSet()
3237 { return checkedNavigableSet(ns.descendingSet(), type); }
3238 public Iterator<E> descendingIterator()
3239 {return checkedNavigableSet(ns.descendingSet(), type).iterator(); }
3240
3241 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
3242 return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type);
3243 }
3244
3245 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
3246 return checkedNavigableSet(ns.headSet(toElement, inclusive), type);
3247 }
3248
3249 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
3250 return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type);
3251 }
3252 }
3253
3254 /**
3255 * Returns a dynamically typesafe view of the specified list.
3256 * Any attempt to insert an element of the wrong type will result in
3257 * an immediate {@link ClassCastException}. Assuming a list contains
3258 * no incorrectly typed elements prior to the time a dynamically typesafe
3259 * view is generated, and that all subsequent access to the list
3260 * takes place through the view, it is <i>guaranteed</i> that the
3261 * list cannot contain an incorrectly typed element.
3262 *
3263 * <p>A discussion of the use of dynamically typesafe views may be
3264 * found in the documentation for the {@link #checkedCollection
3265 * checkedCollection} method.
3266 *
3267 * <p>The returned list will be serializable if the specified list
3268 * is serializable.
3269 *
3270 * <p>Since {@code null} is considered to be a value of any reference
3271 * type, the returned list permits insertion of null elements whenever
3272 * the backing list does.
3273 *
3274 * @param list the list for which a dynamically typesafe view is to be
3275 * returned
3276 * @param type the type of element that {@code list} is permitted to hold
3277 * @return a dynamically typesafe view of the specified list
3278 * @since 1.5
3279 */
3280 public static <E> List<E> checkedList(List<E> list, Class<E> type) {
3281 return (list instanceof RandomAccess ?
3282 new CheckedRandomAccessList<>(list, type) :
3283 new CheckedList<>(list, type));
3284 }
3285
3286 /**
3287 * @serial include
3288 */
3289 static class CheckedList<E>
3290 extends CheckedCollection<E>
3291 implements List<E>
3292 {
3293 private static final long serialVersionUID = 65247728283967356L;
3294 final List<E> list;
3295
3296 CheckedList(List<E> list, Class<E> type) {
3297 super(list, type);
3298 this.list = list;
3299 }
3300
3301 public boolean equals(Object o) { return o == this || list.equals(o); }
3302 public int hashCode() { return list.hashCode(); }
3303 public E get(int index) { return list.get(index); }
3304 public E remove(int index) { return list.remove(index); }
3305 public int indexOf(Object o) { return list.indexOf(o); }
3306 public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
3307
3308 public E set(int index, E element) {
3309 typeCheck(element);
3310 return list.set(index, element);
3311 }
3312
3313 public void add(int index, E element) {
3314 typeCheck(element);
3315 list.add(index, element);
3316 }
3317
3318 public boolean addAll(int index, Collection<? extends E> c) {
3319 return list.addAll(index, checkedCopyOf(c));
3320 }
3321 public ListIterator<E> listIterator() { return listIterator(0); }
3322
3323 public ListIterator<E> listIterator(final int index) {
3324 final ListIterator<E> i = list.listIterator(index);
3325
3326 return new ListIterator<E>() {
3327 public boolean hasNext() { return i.hasNext(); }
3328 public E next() { return i.next(); }
3329 public boolean hasPrevious() { return i.hasPrevious(); }
3330 public E previous() { return i.previous(); }
3331 public int nextIndex() { return i.nextIndex(); }
3332 public int previousIndex() { return i.previousIndex(); }
3333 public void remove() { i.remove(); }
3334
3335 public void set(E e) {
3336 typeCheck(e);
3337 i.set(e);
3338 }
3339
3340 public void add(E e) {
3341 typeCheck(e);
3342 i.add(e);
3343 }
3344
3345 @Override
3346 public void forEachRemaining(Consumer<? super E> action) {
3347 i.forEachRemaining(action);
3348 }
3349 };
3350 }
3351
3352 public List<E> subList(int fromIndex, int toIndex) {
3353 return new CheckedList<>(list.subList(fromIndex, toIndex), type);
3354 }
3355
3356 @Override
3357 public void replaceAll(UnaryOperator<E> operator) {
3358 list.replaceAll(operator);
3359 }
3360 @Override
3361 public void sort(Comparator<? super E> c) {
3362 list.sort(c);
3363 }
3364 }
3365
3366 /**
3367 * @serial include
3368 */
3369 static class CheckedRandomAccessList<E> extends CheckedList<E>
3370 implements RandomAccess
3371 {
3372 private static final long serialVersionUID = 1638200125423088369L;
3373
3374 CheckedRandomAccessList(List<E> list, Class<E> type) {
3375 super(list, type);
3376 }
3377
3378 public List<E> subList(int fromIndex, int toIndex) {
3379 return new CheckedRandomAccessList<>(
3380 list.subList(fromIndex, toIndex), type);
3381 }
3382 }
3383
3384 /**
3385 * Returns a dynamically typesafe view of the specified map.
3386 * Any attempt to insert a mapping whose key or value have the wrong
3387 * type will result in an immediate {@link ClassCastException}.
3388 * Similarly, any attempt to modify the value currently associated with
3389 * a key will result in an immediate {@link ClassCastException},
3390 * whether the modification is attempted directly through the map
3391 * itself, or through a {@link Map.Entry} instance obtained from the
3392 * map's {@link Map#entrySet() entry set} view.
3393 *
3394 * <p>Assuming a map contains no incorrectly typed keys or values
3395 * prior to the time a dynamically typesafe view is generated, and
3396 * that all subsequent access to the map takes place through the view
3397 * (or one of its collection views), it is <i>guaranteed</i> that the
3398 * map cannot contain an incorrectly typed key or value.
3399 *
3400 * <p>A discussion of the use of dynamically typesafe views may be
3401 * found in the documentation for the {@link #checkedCollection
3402 * checkedCollection} method.
3403 *
3404 * <p>The returned map will be serializable if the specified map is
3405 * serializable.
3406 *
3407 * <p>Since {@code null} is considered to be a value of any reference
3408 * type, the returned map permits insertion of null keys or values
3409 * whenever the backing map does.
3410 *
3411 * @param m the map for which a dynamically typesafe view is to be
3412 * returned
3413 * @param keyType the type of key that {@code m} is permitted to hold
3414 * @param valueType the type of value that {@code m} is permitted to hold
3415 * @return a dynamically typesafe view of the specified map
3416 * @since 1.5
3417 */
3418 public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
3419 Class<K> keyType,
3420 Class<V> valueType) {
3421 return new CheckedMap<>(m, keyType, valueType);
3422 }
3423
3424
3425 /**
3426 * @serial include
3427 */
3428 private static class CheckedMap<K,V>
3429 implements Map<K,V>, Serializable
3430 {
3431 private static final long serialVersionUID = 5742860141034234728L;
3432
3433 private final Map<K, V> m;
3434 final Class<K> keyType;
3435 final Class<V> valueType;
3436
3437 private void typeCheck(Object key, Object value) {
3438 if (key != null && !keyType.isInstance(key))
3439 throw new ClassCastException(badKeyMsg(key));
3440
3441 if (value != null && !valueType.isInstance(value))
3442 throw new ClassCastException(badValueMsg(value));
3443 }
3444
3445 private BiFunction<? super K, ? super V, ? extends V> typeCheck(
3446 BiFunction<? super K, ? super V, ? extends V> func) {
3447 Objects.requireNonNull(func);
3448 return (k, v) -> {
3449 V newValue = func.apply(k, v);
3450 typeCheck(k, newValue);
3451 return newValue;
3452 };
3453 }
3454
3455 private String badKeyMsg(Object key) {
3456 return "Attempt to insert " + key.getClass() +
3457 " key into map with key type " + keyType;
3458 }
3459
3460 private String badValueMsg(Object value) {
3461 return "Attempt to insert " + value.getClass() +
3462 " value into map with value type " + valueType;
3463 }
3464
3465 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
3466 this.m = Objects.requireNonNull(m);
3467 this.keyType = Objects.requireNonNull(keyType);
3468 this.valueType = Objects.requireNonNull(valueType);
3469 }
3470
3471 public int size() { return m.size(); }
3472 public boolean isEmpty() { return m.isEmpty(); }
3473 public boolean containsKey(Object key) { return m.containsKey(key); }
3474 public boolean containsValue(Object v) { return m.containsValue(v); }
3475 public V get(Object key) { return m.get(key); }
3476 public V remove(Object key) { return m.remove(key); }
3477 public void clear() { m.clear(); }
3478 public Set<K> keySet() { return m.keySet(); }
3479 public Collection<V> values() { return m.values(); }
3480 public boolean equals(Object o) { return o == this || m.equals(o); }
3481 public int hashCode() { return m.hashCode(); }
3482 public String toString() { return m.toString(); }
3483
3484 public V put(K key, V value) {
3485 typeCheck(key, value);
3486 return m.put(key, value);
3487 }
3488
3489 @SuppressWarnings("unchecked")
3490 public void putAll(Map<? extends K, ? extends V> t) {
3491 // Satisfy the following goals:
3492 // - good diagnostics in case of type mismatch
3493 // - all-or-nothing semantics
3494 // - protection from malicious t
3495 // - correct behavior if t is a concurrent map
3496 Object[] entries = t.entrySet().toArray();
3497 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length);
3498 for (Object o : entries) {
3499 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3500 Object k = e.getKey();
3501 Object v = e.getValue();
3502 typeCheck(k, v);
3503 checked.add(
3504 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v));
3505 }
3506 for (Map.Entry<K,V> e : checked)
3507 m.put(e.getKey(), e.getValue());
3508 }
3509
3510 private transient Set<Map.Entry<K,V>> entrySet = null;
3511
3512 public Set<Map.Entry<K,V>> entrySet() {
3513 if (entrySet==null)
3514 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
3515 return entrySet;
3516 }
3517
3518 // Override default methods in Map
3519 @Override
3520 public void forEach(BiConsumer<? super K, ? super V> action) {
3521 m.forEach(action);
3522 }
3523
3524 @Override
3525 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
3526 m.replaceAll(typeCheck(function));
3527 }
3528
3529 @Override
3530 public V putIfAbsent(K key, V value) {
3531 typeCheck(key, value);
3532 return m.putIfAbsent(key, value);
3533 }
3534
3535 @Override
3536 public boolean remove(Object key, Object value) {
3537 return m.remove(key, value);
3538 }
3539
3540 @Override
3541 public boolean replace(K key, V oldValue, V newValue) {
3542 typeCheck(key, newValue);
3543 return m.replace(key, oldValue, newValue);
3544 }
3545
3546 @Override
3547 public V replace(K key, V value) {
3548 typeCheck(key, value);
3549 return m.replace(key, value);
3550 }
3551
3552 @Override
3553 public V computeIfAbsent(K key,
3554 Function<? super K, ? extends V> mappingFunction) {
3555 Objects.requireNonNull(mappingFunction);
3556 return m.computeIfAbsent(key, k -> {
3557 V value = mappingFunction.apply(k);
3558 typeCheck(k, value);
3559 return value;
3560 });
3561 }
3562
3563 @Override
3564 public V computeIfPresent(K key,
3565 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3566 return m.computeIfPresent(key, typeCheck(remappingFunction));
3567 }
3568
3569 @Override
3570 public V compute(K key,
3571 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3572 return m.compute(key, typeCheck(remappingFunction));
3573 }
3574
3575 @Override
3576 public V merge(K key, V value,
3577 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
3578 Objects.requireNonNull(remappingFunction);
3579 return m.merge(key, value, (v1, v2) -> {
3580 V newValue = remappingFunction.apply(v1, v2);
3581 typeCheck(null, newValue);
3582 return newValue;
3583 });
3584 }
3585
3586 /**
3587 * We need this class in addition to CheckedSet as Map.Entry permits
3588 * modification of the backing Map via the setValue operation. This
3589 * class is subtle: there are many possible attacks that must be
3590 * thwarted.
3591 *
3592 * @serial exclude
3593 */
3594 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
3595 private final Set<Map.Entry<K,V>> s;
3596 private final Class<V> valueType;
3597
3598 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
3599 this.s = s;
3600 this.valueType = valueType;
3601 }
3602
3603 public int size() { return s.size(); }
3604 public boolean isEmpty() { return s.isEmpty(); }
3605 public String toString() { return s.toString(); }
3606 public int hashCode() { return s.hashCode(); }
3607 public void clear() { s.clear(); }
3608
3609 public boolean add(Map.Entry<K, V> e) {
3610 throw new UnsupportedOperationException();
3611 }
3612 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
3613 throw new UnsupportedOperationException();
3614 }
3615
3616 public Iterator<Map.Entry<K,V>> iterator() {
3617 final Iterator<Map.Entry<K, V>> i = s.iterator();
3618 final Class<V> valueType = this.valueType;
3619
3620 return new Iterator<Map.Entry<K,V>>() {
3621 public boolean hasNext() { return i.hasNext(); }
3622 public void remove() { i.remove(); }
3623
3624 public Map.Entry<K,V> next() {
3625 return checkedEntry(i.next(), valueType);
3626 }
3627 };
3628 }
3629
3630 @SuppressWarnings("unchecked")
3631 public Object[] toArray() {
3632 Object[] source = s.toArray();
3633
3634 /*
3635 * Ensure that we don't get an ArrayStoreException even if
3636 * s.toArray returns an array of something other than Object
3637 */
3638 Object[] dest = (CheckedEntry.class.isInstance(
3639 source.getClass().getComponentType()) ? source :
3640 new Object[source.length]);
3641
3642 for (int i = 0; i < source.length; i++)
3643 dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
3644 valueType);
3645 return dest;
3646 }
3647
3648 @SuppressWarnings("unchecked")
3649 public <T> T[] toArray(T[] a) {
3650 // We don't pass a to s.toArray, to avoid window of
3651 // vulnerability wherein an unscrupulous multithreaded client
3652 // could get his hands on raw (unwrapped) Entries from s.
3653 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
3654
3655 for (int i=0; i<arr.length; i++)
3656 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
3657 valueType);
3658 if (arr.length > a.length)
3659 return arr;
3660
3661 System.arraycopy(arr, 0, a, 0, arr.length);
3662 if (a.length > arr.length)
3663 a[arr.length] = null;
3664 return a;
3665 }
3666
3667 /**
3668 * This method is overridden to protect the backing set against
3669 * an object with a nefarious equals function that senses
3670 * that the equality-candidate is Map.Entry and calls its
3671 * setValue method.
3672 */
3673 public boolean contains(Object o) {
3674 if (!(o instanceof Map.Entry))
3675 return false;
3676 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3677 return s.contains(
3678 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
3679 }
3680
3681 /**
3682 * The bulk collection methods are overridden to protect
3683 * against an unscrupulous collection whose contains(Object o)
3684 * method senses when o is a Map.Entry, and calls o.setValue.
3685 */
3686 public boolean containsAll(Collection<?> c) {
3687 for (Object o : c)
3688 if (!contains(o)) // Invokes safe contains() above
3689 return false;
3690 return true;
3691 }
3692
3693 public boolean remove(Object o) {
3694 if (!(o instanceof Map.Entry))
3695 return false;
3696 return s.remove(new AbstractMap.SimpleImmutableEntry
3697 <>((Map.Entry<?,?>)o));
3698 }
3699
3700 public boolean removeAll(Collection<?> c) {
3701 return batchRemove(c, false);
3702 }
3703 public boolean retainAll(Collection<?> c) {
3704 return batchRemove(c, true);
3705 }
3706 private boolean batchRemove(Collection<?> c, boolean complement) {
3707 boolean modified = false;
3708 Iterator<Map.Entry<K,V>> it = iterator();
3709 while (it.hasNext()) {
3710 if (c.contains(it.next()) != complement) {
3711 it.remove();
3712 modified = true;
3713 }
3714 }
3715 return modified;
3716 }
3717
3718 public boolean equals(Object o) {
3719 if (o == this)
3720 return true;
3721 if (!(o instanceof Set))
3722 return false;
3723 Set<?> that = (Set<?>) o;
3724 return that.size() == s.size()
3725 && containsAll(that); // Invokes safe containsAll() above
3726 }
3727
3728 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
3729 Class<T> valueType) {
3730 return new CheckedEntry<>(e, valueType);
3731 }
3732
3733 /**
3734 * This "wrapper class" serves two purposes: it prevents
3735 * the client from modifying the backing Map, by short-circuiting
3736 * the setValue method, and it protects the backing Map against
3737 * an ill-behaved Map.Entry that attempts to modify another
3738 * Map.Entry when asked to perform an equality check.
3739 */
3740 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
3741 private final Map.Entry<K, V> e;
3742 private final Class<T> valueType;
3743
3744 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
3745 this.e = e;
3746 this.valueType = valueType;
3747 }
3748
3749 public K getKey() { return e.getKey(); }
3750 public V getValue() { return e.getValue(); }
3751 public int hashCode() { return e.hashCode(); }
3752 public String toString() { return e.toString(); }
3753
3754 public V setValue(V value) {
3755 if (value != null && !valueType.isInstance(value))
3756 throw new ClassCastException(badValueMsg(value));
3757 return e.setValue(value);
3758 }
3759
3760 private String badValueMsg(Object value) {
3761 return "Attempt to insert " + value.getClass() +
3762 " value into map with value type " + valueType;
3763 }
3764
3765 public boolean equals(Object o) {
3766 if (o == this)
3767 return true;
3768 if (!(o instanceof Map.Entry))
3769 return false;
3770 return e.equals(new AbstractMap.SimpleImmutableEntry
3771 <>((Map.Entry<?,?>)o));
3772 }
3773 }
3774 }
3775 }
3776
3777 /**
3778 * Returns a dynamically typesafe view of the specified sorted map.
3779 * Any attempt to insert a mapping whose key or value have the wrong
3780 * type will result in an immediate {@link ClassCastException}.
3781 * Similarly, any attempt to modify the value currently associated with
3782 * a key will result in an immediate {@link ClassCastException},
3783 * whether the modification is attempted directly through the map
3784 * itself, or through a {@link Map.Entry} instance obtained from the
3785 * map's {@link Map#entrySet() entry set} view.
3786 *
3787 * <p>Assuming a map contains no incorrectly typed keys or values
3788 * prior to the time a dynamically typesafe view is generated, and
3789 * that all subsequent access to the map takes place through the view
3790 * (or one of its collection views), it is <i>guaranteed</i> that the
3791 * map cannot contain an incorrectly typed key or value.
3792 *
3793 * <p>A discussion of the use of dynamically typesafe views may be
3794 * found in the documentation for the {@link #checkedCollection
3795 * checkedCollection} method.
3796 *
3797 * <p>The returned map will be serializable if the specified map is
3798 * serializable.
3799 *
3800 * <p>Since {@code null} is considered to be a value of any reference
3801 * type, the returned map permits insertion of null keys or values
3802 * whenever the backing map does.
3803 *
3804 * @param m the map for which a dynamically typesafe view is to be
3805 * returned
3806 * @param keyType the type of key that {@code m} is permitted to hold
3807 * @param valueType the type of value that {@code m} is permitted to hold
3808 * @return a dynamically typesafe view of the specified map
3809 * @since 1.5
3810 */
3811 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
3812 Class<K> keyType,
3813 Class<V> valueType) {
3814 return new CheckedSortedMap<>(m, keyType, valueType);
3815 }
3816
3817 /**
3818 * @serial include
3819 */
3820 static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
3821 implements SortedMap<K,V>, Serializable
3822 {
3823 private static final long serialVersionUID = 1599671320688067438L;
3824
3825 private final SortedMap<K, V> sm;
3826
3827 CheckedSortedMap(SortedMap<K, V> m,
3828 Class<K> keyType, Class<V> valueType) {
3829 super(m, keyType, valueType);
3830 sm = m;
3831 }
3832
3833 public Comparator<? super K> comparator() { return sm.comparator(); }
3834 public K firstKey() { return sm.firstKey(); }
3835 public K lastKey() { return sm.lastKey(); }
3836
3837 public SortedMap<K,V> subMap(K fromKey, K toKey) {
3838 return checkedSortedMap(sm.subMap(fromKey, toKey),
3839 keyType, valueType);
3840 }
3841 public SortedMap<K,V> headMap(K toKey) {
3842 return checkedSortedMap(sm.headMap(toKey), keyType, valueType);
3843 }
3844 public SortedMap<K,V> tailMap(K fromKey) {
3845 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType);
3846 }
3847 }
3848
3849 /**
3850 * Returns a dynamically typesafe view of the specified navigable map.
3851 * Any attempt to insert a mapping whose key or value have the wrong
3852 * type will result in an immediate {@link ClassCastException}.
3853 * Similarly, any attempt to modify the value currently associated with
3854 * a key will result in an immediate {@link ClassCastException},
3855 * whether the modification is attempted directly through the map
3856 * itself, or through a {@link Map.Entry} instance obtained from the
3857 * map's {@link Map#entrySet() entry set} view.
3858 *
3859 * <p>Assuming a map contains no incorrectly typed keys or values
3860 * prior to the time a dynamically typesafe view is generated, and
3861 * that all subsequent access to the map takes place through the view
3862 * (or one of its collection views), it is <em>guaranteed</em> that the
3863 * map cannot contain an incorrectly typed key or value.
3864 *
3865 * <p>A discussion of the use of dynamically typesafe views may be
3866 * found in the documentation for the {@link #checkedCollection
3867 * checkedCollection} method.
3868 *
3869 * <p>The returned map will be serializable if the specified map is
3870 * serializable.
3871 *
3872 * <p>Since {@code null} is considered to be a value of any reference
3873 * type, the returned map permits insertion of null keys or values
3874 * whenever the backing map does.
3875 *
3876 * @param <K> type of map keys
3877 * @param <V> type of map values
3878 * @param m the map for which a dynamically typesafe view is to be
3879 * returned
3880 * @param keyType the type of key that {@code m} is permitted to hold
3881 * @param valueType the type of value that {@code m} is permitted to hold
3882 * @return a dynamically typesafe view of the specified map
3883 * @since 1.8
3884 */
3885 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m,
3886 Class<K> keyType,
3887 Class<V> valueType) {
3888 return new CheckedNavigableMap<>(m, keyType, valueType);
3889 }
3890
3891 /**
3892 * @serial include
3893 */
3894 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V>
3895 implements NavigableMap<K,V>, Serializable
3896 {
3897 private static final long serialVersionUID = -4852462692372534096L;
3898
3899 private final NavigableMap<K, V> nm;
3900
3901 CheckedNavigableMap(NavigableMap<K, V> m,
3902 Class<K> keyType, Class<V> valueType) {
3903 super(m, keyType, valueType);
3904 nm = m;
3905 }
3906
3907 public Comparator<? super K> comparator() { return nm.comparator(); }
3908 public K firstKey() { return nm.firstKey(); }
3909 public K lastKey() { return nm.lastKey(); }
3910
3911 public NavigableMap<K,V> subMap(K fromKey, K toKey) {
3912 return checkedNavigableMap((NavigableMap<K,V>)nm.subMap(fromKey, toKey),
3913 keyType, valueType);
3914 }
3915 public NavigableMap<K,V> headMap(K toKey) {
3916 return checkedNavigableMap((NavigableMap<K,V>)nm.headMap(toKey), keyType, valueType);
3917 }
3918 public NavigableMap<K,V> tailMap(K fromKey) {
3919 return checkedNavigableMap((NavigableMap<K,V>)nm.tailMap(fromKey), keyType, valueType);
3920 }
3921
3922 @Override
3923 public Entry<K, V> lowerEntry(K key) {
3924 return new CheckedMap.CheckedEntrySet.CheckedEntry(nm.lowerEntry(key), valueType);
3925 }
3926
3927 @Override
3928 public K lowerKey(K key) {
3929 return nm.lowerKey(key);
3930 }
3931
3932 @Override
3933 public Entry<K, V> floorEntry(K key) {
3934 return new CheckedMap.CheckedEntrySet.CheckedEntry(nm.lowerEntry(key), valueType);
3935 }
3936
3937 @Override
3938 public K floorKey(K key) {
3939 return nm.floorKey(key);
3940 }
3941
3942 @Override
3943 public Entry<K, V> ceilingEntry(K key) {
3944 return new CheckedMap.CheckedEntrySet.CheckedEntry(nm.ceilingEntry(key), valueType);
3945 }
3946
3947 @Override
3948 public K ceilingKey(K key) {
3949 return nm.ceilingKey(key);
3950 }
3951
3952 @Override
3953 public Entry<K, V> higherEntry(K key) {
3954 return new CheckedMap.CheckedEntrySet.CheckedEntry(nm.higherEntry(key), valueType);
3955 }
3956
3957 @Override
3958 public K higherKey(K key) {
3959 return nm.higherKey(key);
3960 }
3961
3962 @Override
3963 public Entry<K, V> firstEntry() {
3964 return new CheckedMap.CheckedEntrySet.CheckedEntry(nm.firstEntry(), valueType);
3965 }
3966
3967 @Override
3968 public Entry<K, V> lastEntry() {
3969 return new CheckedMap.CheckedEntrySet.CheckedEntry(nm.lastEntry(), valueType);
3970 }
3971
3972 @Override
3973 public Entry<K, V> pollFirstEntry() {
3974 Entry<K,V> entry = nm.pollFirstEntry();
3975 return (null == entry) ? null : new CheckedMap.CheckedEntrySet.CheckedEntry(entry, valueType);
3976 }
3977
3978 @Override
3979 public Entry<K, V> pollLastEntry() {
3980 Entry<K,V> entry = nm.pollLastEntry();
3981 return (null == entry) ? null : new CheckedMap.CheckedEntrySet.CheckedEntry(entry, valueType);
3982 }
3983
3984 @Override
3985 public NavigableMap<K, V> descendingMap() {
3986 return checkedNavigableMap(nm.descendingMap(), keyType, valueType);
3987 }
3988
3989 @Override
3990 public NavigableSet<K> navigableKeySet() {
3991 return checkedNavigableSet(nm.navigableKeySet(), keyType);
3992 }
3993
3994 @Override
3995 public NavigableSet<K> descendingKeySet() {
3996 return checkedNavigableSet(nm.descendingKeySet(), keyType);
3997 }
3998
3999 @Override
4000 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
4001 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType);
4002 }
4003
4004 @Override
4005 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
4006 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType);
4007 }
4008
4009 @Override
4010 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
4011 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType);
4012 }
4013 }
4014
4015 // Empty collections
4016
4017 /**
4018 * Returns an iterator that has no elements. More precisely,
4019 *
4020 * <ul compact>
4021 *
4022 * <li>{@link Iterator#hasNext hasNext} always returns {@code
4023 * false}.
4024 *
4025 * <li>{@link Iterator#next next} always throws {@link
4026 * NoSuchElementException}.
4027 *
4028 * <li>{@link Iterator#remove remove} always throws {@link
4029 * IllegalStateException}.
4030 *
4031 * </ul>
4032 *
4033 * <p>Implementations of this method are permitted, but not
4034 * required, to return the same object from multiple invocations.
4035 *
4036 * @return an empty iterator
4037 * @since 1.7
4038 */
4039 @SuppressWarnings("unchecked")
4040 public static <T> Iterator<T> emptyIterator() {
4041 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
4042 }
4043
4044 private static class EmptyIterator<E> implements Iterator<E> {
4045 static final EmptyIterator<Object> EMPTY_ITERATOR
4046 = new EmptyIterator<>();
4047
4048 public boolean hasNext() { return false; }
4049 public E next() { throw new NoSuchElementException(); }
4050 public void remove() { throw new IllegalStateException(); }
4051 @Override
4052 public void forEachRemaining(Consumer<? super E> action) {
4053 Objects.requireNonNull(action);
4054 }
4055 }
4056
4057 /**
4058 * Returns a list iterator that has no elements. More precisely,
4059 *
4060 * <ul compact>
4061 *
4062 * <li>{@link Iterator#hasNext hasNext} and {@link
4063 * ListIterator#hasPrevious hasPrevious} always return {@code
4064 * false}.
4065 *
4066 * <li>{@link Iterator#next next} and {@link ListIterator#previous
4067 * previous} always throw {@link NoSuchElementException}.
4068 *
4069 * <li>{@link Iterator#remove remove} and {@link ListIterator#set
4070 * set} always throw {@link IllegalStateException}.
4071 *
4072 * <li>{@link ListIterator#add add} always throws {@link
4073 * UnsupportedOperationException}.
4074 *
4075 * <li>{@link ListIterator#nextIndex nextIndex} always returns
4076 * {@code 0} .
4077 *
4078 * <li>{@link ListIterator#previousIndex previousIndex} always
4079 * returns {@code -1}.
4080 *
4081 * </ul>
4082 *
4083 * <p>Implementations of this method are permitted, but not
4084 * required, to return the same object from multiple invocations.
4085 *
4086 * @return an empty list iterator
4087 * @since 1.7
4088 */
4089 @SuppressWarnings("unchecked")
4090 public static <T> ListIterator<T> emptyListIterator() {
4091 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
4092 }
4093
4094 private static class EmptyListIterator<E>
4095 extends EmptyIterator<E>
4096 implements ListIterator<E>
4097 {
4098 static final EmptyListIterator<Object> EMPTY_ITERATOR
4099 = new EmptyListIterator<>();
4100
4101 public boolean hasPrevious() { return false; }
4102 public E previous() { throw new NoSuchElementException(); }
4103 public int nextIndex() { return 0; }
4104 public int previousIndex() { return -1; }
4105 public void set(E e) { throw new IllegalStateException(); }
4106 public void add(E e) { throw new UnsupportedOperationException(); }
4107 }
4108
4109 /**
4110 * Returns an enumeration that has no elements. More precisely,
4111 *
4112 * <ul compact>
4113 *
4114 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
4115 * returns {@code false}.
4116 *
4117 * <li> {@link Enumeration#nextElement nextElement} always throws
4118 * {@link NoSuchElementException}.
4119 *
4120 * </ul>
4121 *
4122 * <p>Implementations of this method are permitted, but not
4123 * required, to return the same object from multiple invocations.
4124 *
4125 * @return an empty enumeration
4126 * @since 1.7
4127 */
4128 @SuppressWarnings("unchecked")
4129 public static <T> Enumeration<T> emptyEnumeration() {
4130 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
4131 }
4132
4133 private static class EmptyEnumeration<E> implements Enumeration<E> {
4134 static final EmptyEnumeration<Object> EMPTY_ENUMERATION
4135 = new EmptyEnumeration<>();
4136
4137 public boolean hasMoreElements() { return false; }
4138 public E nextElement() { throw new NoSuchElementException(); }
4139 }
4140
4141 /**
4142 * The empty set (immutable). This set is serializable.
4143 *
4144 * @see #emptySet()
4145 */
4146 @SuppressWarnings("rawtypes")
4147 public static final Set EMPTY_SET = new EmptySet<>();
4148
4149 /**
4150 * Returns the empty set (immutable). This set is serializable.
4151 * Unlike the like-named field, this method is parameterized.
4152 *
4153 * <p>This example illustrates the type-safe way to obtain an empty set:
4154 * <pre>
4155 * Set<String> s = Collections.emptySet();
4156 * </pre>
4157 * @implNote Implementations of this method need not create a separate
4158 * {@code Set} object for each call. Using this method is likely to have
4159 * comparable cost to using the like-named field. (Unlike this method, the
4160 * field does not provide type safety.)
4161 *
4162 * @return the empty set
4163 * @see #EMPTY_SET
4164 * @since 1.5
4165 */
4166 @SuppressWarnings("unchecked")
4167 public static final <T> Set<T> emptySet() {
4168 return (Set<T>) EMPTY_SET;
4169 }
4170
4171 /**
4172 * @serial include
4173 */
4174 private static class EmptySet<E>
4175 extends AbstractSet<E>
4176 implements Serializable
4177 {
4178 private static final long serialVersionUID = 1582296315990362920L;
4179
4180 public Iterator<E> iterator() { return emptyIterator(); }
4181
4182 public int size() {return 0;}
4183 public boolean isEmpty() {return true;}
4184
4185 public boolean contains(Object obj) {return false;}
4186 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4187
4188 public Object[] toArray() { return new Object[0]; }
4189
4190 public <T> T[] toArray(T[] a) {
4191 if (a.length > 0)
4192 a[0] = null;
4193 return a;
4194 }
4195
4196 // Override default methods in Collection
4197 @Override
4198 public void forEach(Consumer<? super E> action) {
4199 Objects.requireNonNull(action);
4200 }
4201 @Override
4202 public boolean removeIf(Predicate<? super E> filter) {
4203 Objects.requireNonNull(filter);
4204 return false;
4205 }
4206 @Override
4207 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4208
4209 // Preserves singleton property
4210 private Object readResolve() {
4211 return EMPTY_SET;
4212 }
4213 }
4214
4215 /**
4216 * Returns an empty sorted set (immutable). This set is serializable.
4217 *
4218 * <p>This example illustrates the type-safe way to obtain an empty
4219 * sorted set:
4220 * <pre> {@code
4221 * SortedSet<String> s = Collections.emptySortedSet();
4222 * }</pre>
4223 *
4224 * @implNote Implementations of this method need not create a separate
4225 * {@code SortedSet} object for each call.
4226 *
4227 * @param <E> type of elements, if there were any, in the set
4228 * @return the empty sorted set
4229 * @since 1.8
4230 */
4231 @SuppressWarnings("unchecked")
4232 public static <E> SortedSet<E> emptySortedSet() {
4233 return (SortedSet<E>) EmptyNavigableSet.EMPTY_NAVIGABLE_SET;
4234 }
4235
4236 /**
4237 * Returns an empty navigable set (immutable). This set is serializable.
4238 *
4239 * <p>This example illustrates the type-safe way to obtain an empty
4240 * navigable set:
4241 * <pre> {@code
4242 * NavigableSet<String> s = Collections.emptyNavigableSet();
4243 * }</pre>
4244 *
4245 * @implNote Implementations of this method need not
4246 * create a separate {@code NavigableSet} object for each call.
4247 *
4248 * @param <E> type of elements, if there were any, in the set
4249 * @return the empty navigable set
4250 * @since 1.8
4251 */
4252 @SuppressWarnings("unchecked")
4253 public static <E> NavigableSet<E> emptyNavigableSet() {
4254 return (NavigableSet<E>) EmptyNavigableSet.EMPTY_NAVIGABLE_SET;
4255 }
4256
4257 /**
4258 * The empty list (immutable). This list is serializable.
4259 *
4260 * @see #emptyList()
4261 */
4262 @SuppressWarnings("rawtypes")
4263 public static final List EMPTY_LIST = new EmptyList<>();
4264
4265 /**
4266 * Returns the empty list (immutable). This list is serializable.
4267 *
4268 * <p>This example illustrates the type-safe way to obtain an empty list:
4269 * <pre>
4270 * List<String> s = Collections.emptyList();
4271 * </pre>
4272 * Implementation note: Implementations of this method need not
4273 * create a separate <tt>List</tt> object for each call. Using this
4274 * method is likely to have comparable cost to using the like-named
4275 * field. (Unlike this method, the field does not provide type safety.)
4276 *
4277 * @see #EMPTY_LIST
4278 * @since 1.5
4279 */
4280 @SuppressWarnings("unchecked")
4281 public static final <T> List<T> emptyList() {
4282 return (List<T>) EMPTY_LIST;
4283 }
4284
4285 /**
4286 * @serial include
4287 */
4288 private static class EmptyList<E>
4289 extends AbstractList<E>
4290 implements RandomAccess, Serializable {
4291 private static final long serialVersionUID = 8842843931221139166L;
4292
4293 public Iterator<E> iterator() {
4294 return emptyIterator();
4295 }
4296 public ListIterator<E> listIterator() {
4297 return emptyListIterator();
4298 }
4299
4300 public int size() {return 0;}
4301 public boolean isEmpty() {return true;}
4302
4303 public boolean contains(Object obj) {return false;}
4304 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4305
4306 public Object[] toArray() { return new Object[0]; }
4307
4308 public <T> T[] toArray(T[] a) {
4309 if (a.length > 0)
4310 a[0] = null;
4311 return a;
4312 }
4313
4314 public E get(int index) {
4315 throw new IndexOutOfBoundsException("Index: "+index);
4316 }
4317
4318 public boolean equals(Object o) {
4319 return (o instanceof List) && ((List<?>)o).isEmpty();
4320 }
4321
4322 public int hashCode() { return 1; }
4323
4324 @Override
4325 public boolean removeIf(Predicate<? super E> filter) {
4326 Objects.requireNonNull(filter);
4327 return false;
4328 }
4329 @Override
4330 public void replaceAll(UnaryOperator<E> operator) {
4331 Objects.requireNonNull(operator);
4332 }
4333 @Override
4334 public void sort(Comparator<? super E> c) {
4335 Objects.requireNonNull(c);
4336 }
4337
4338 // Override default methods in Collection
4339 @Override
4340 public void forEach(Consumer<? super E> action) {
4341 Objects.requireNonNull(action);
4342 }
4343
4344 @Override
4345 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4346
4347 // Preserves singleton property
4348 private Object readResolve() {
4349 return EMPTY_LIST;
4350 }
4351 }
4352
4353 /**
4354 * An empty navigable map with enforced bounds upon the key set. The bounds
4355 * are generated via the various sub-map operations and enforced on
4356 * subsequent sub-map operations.
4357 *
4358 * @serial include
4359 *
4360 * @param <K> type of keys, if there were any, and bounds
4361 * @param <V> type of values, if there were any
4362 */
4363 private static class BoundedEmptyNavigableMap<K,V> extends EmptyNavigableMap<K,V>
4364 implements Serializable {
4365
4366 private static final long serialVersionUID = 5065418537829651507L;
4367
4368 /**
4369 * Our bounded keyset.
4370 */
4371 final BoundedEmptyNavigableSet keySet;
4372
4373 private BoundedEmptyNavigableMap(BoundedEmptyNavigableSet keySet) {
4374 this.keySet = Objects.requireNonNull(keySet);
4375 }
4376
4377 public Comparator<? super K> comparator()
4378 { return keySet.comparator(); }
4379
4380 @Override
4381 public NavigableMap<K, V> descendingMap() {
4382 NavigableSet<K> descending = keySet.descendingSet();
4383
4384 if(descending == Collections.emptyNavigableSet()) {
4385 return Collections.emptyNavigableMap();
4386 } else {
4387 return new BoundedEmptyNavigableMap((BoundedEmptyNavigableSet<K>) descending);
4388 }
4389 }
4390
4391 public BoundedEmptyNavigableSet<K> navigableKeySet() { return keySet; }
4392 public EmptyNavigableSet<K> descendingKeySet()
4393 { return keySet.descendingSet(); }
4394
4395 @Override
4396 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
4397 return new BoundedEmptyNavigableMap(keySet.subSet(
4398 fromKey, fromInclusive,
4399 toKey, toInclusive));
4400 }
4401
4402 @Override
4403 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
4404 return new BoundedEmptyNavigableMap(
4405 keySet.headSet(toKey, inclusive));
4406 }
4407
4408 @Override
4409 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
4410 return new BoundedEmptyNavigableMap(
4411 keySet.tailSet(fromKey, inclusive));
4412 }
4413 }
4414
4415 /**
4416 * @serial include
4417 *
4418 * @param <E> type of elements, if there were any
4419 */
4420 private static class EmptyNavigableSet<E> extends EmptySet<E>
4421 implements NavigableSet<E>, Serializable {
4422 private static final long serialVersionUID = -6291252904449939134L;
4423
4424 @SuppressWarnings("rawtypes")
4425 private static final NavigableSet EMPTY_NAVIGABLE_SET =
4426 new EmptyNavigableSet();
4427
4428 EmptyNavigableSet() { }
4429
4430 @Override
4431 public boolean contains(Object obj) {
4432 Comparable<E> e = (Comparable<E>) Objects.requireNonNull(obj);
4433 return obj != e;
4434 }
4435
4436 // Preserves singleton property
4437 private Object readResolve()
4438 { return Collections.emptyNavigableSet(); }
4439 public E lower(E e) { return null; }
4440 public E floor(E e) { return null; }
4441 public E ceiling(E e) { return null; }
4442 public E higher(E e) { return null; }
4443 public E pollFirst() { throw new UnsupportedOperationException(); }
4444 public E pollLast() { throw new UnsupportedOperationException(); }
4445
4446 public EmptyNavigableSet<E> descendingSet() {
4447 return new BoundedEmptyNavigableSet(null, false, null, false, true);
4448 }
4449
4450 public Iterator<E> descendingIterator()
4451 { return Collections.emptyIterator(); }
4452
4453 public BoundedEmptyNavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
4454 return new BoundedEmptyNavigableSet<>(
4455 (Comparable<E>) Objects.requireNonNull(fromElement), fromInclusive,
4456 (Comparable<E>) Objects.requireNonNull(toElement), toInclusive,
4457 false);
4458 }
4459
4460 public BoundedEmptyNavigableSet<E> headSet(E toElement, boolean inclusive) {
4461 return new BoundedEmptyNavigableSet<>(
4462 null, false,
4463 (Comparable<E>) Objects.requireNonNull(toElement), inclusive,
4464 false);
4465 }
4466
4467 public BoundedEmptyNavigableSet<E> tailSet(E fromElement, boolean inclusive) {
4468 return new BoundedEmptyNavigableSet<>(
4469 (Comparable<E>) Objects.requireNonNull(fromElement), inclusive,
4470 null, false,
4471 false);
4472 }
4473
4474 public final SortedSet<E> subSet(E fromElement, E toElement)
4475 { return subSet(fromElement, true, toElement, false); }
4476 public final SortedSet<E> headSet(E toElement)
4477 { return headSet(toElement, true); }
4478 public final SortedSet<E> tailSet(E fromElement)
4479 { return tailSet(fromElement, false); }
4480
4481 public Comparator<? super E> comparator() { return null; }
4482 public E first() { throw new NoSuchElementException(); }
4483 public E last() { throw new NoSuchElementException(); }
4484 }
4485
4486 /**
4487 * An empty NavigableSet but bounds are maintained. If you try to sub-set
4488 * outside the bounds you will get an IllegalArgumentException.
4489 *
4490 * @serial include
4491 *
4492 * @param <E> type of elements, if there were any, and bounds
4493 */
4494 private static class BoundedEmptyNavigableSet<E> extends EmptyNavigableSet<E>
4495 implements Serializable {
4496 private static final long serialVersionUID = 3393358742248855583L;
4497
4498 /**
4499 * {@code true} if lowerBound is "greater" than upperBound.
4500 */
4501 final boolean descending;
4502 /**
4503 * {@code true} if lowerBound is inclusive.
4504 */
4505 final boolean lowerInclusive;
4506 /**
4507 * {@code true} if upperBound is inclusive.
4508 */
4509 final boolean upperInclusive;
4510 /**
4511 * The lower bound of the set.
4512 */
4513 final Comparable<E> lowerBound;
4514 /**
4515 * The upper bound of the set.
4516 */
4517 final Comparable<E> upperBound;
4518
4519 public BoundedEmptyNavigableSet(
4520 Comparable<E> fromElement, boolean lowerInclusive,
4521 Comparable<E> toElement, boolean upperInclusive,
4522 boolean descending) {
4523 this.descending = descending;
4524
4525 if ((fromElement != null) && (toElement != null)) {
4526 // both bounds are present we need to ensure that they make
4527 // sense.
4528 int fromCompared = Integer.signum(fromElement.compareTo((E)toElement));
4529 int toCompared = Integer.signum(toElement.compareTo((E)fromElement));
4530
4531 if(fromCompared != -toCompared) {
4532 throw new IllegalArgumentException("inconsistent compareTo");
4533 }
4534
4535 if (descending) {
4536 if (fromCompared < 0) {
4537 throw new IllegalArgumentException();
4538 }
4539 } else {
4540 if (fromCompared > 0) {
4541 throw new IllegalArgumentException();
4542 }
4543 }
4544 }
4545
4546 this.lowerBound = fromElement;
4547 this.lowerInclusive = lowerInclusive;
4548 this.upperBound = toElement;
4549 this.upperInclusive = upperInclusive;
4550 }
4551
4552 @Override
4553 public Comparator<? super E> comparator()
4554 { return descending ? Collections.reverseOrder() : null; }
4555
4556 private Comparable<E> inBounds(E element) {
4557 if (!descending) {
4558 if (null != lowerBound) {
4559 if (lowerInclusive) {
4560 if (lowerBound.compareTo(element) > 0) {
4561 throw new IllegalArgumentException("out of bounds");
4562 }
4563 } else {
4564 if (lowerBound.compareTo(element) >= 0) {
4565 throw new IllegalArgumentException("out of bounds");
4566 }
4567 }
4568 }
4569
4570 if (null != upperBound) {
4571 if (upperInclusive) {
4572 if (upperBound.compareTo(element) < 0) {
4573 throw new IllegalArgumentException("out of bounds");
4574 }
4575 } else {
4576 if (upperBound.compareTo(element) <= 0) {
4577 throw new IllegalArgumentException("out of bounds");
4578 }
4579 }
4580 }
4581 } else {
4582 if (null != lowerBound) {
4583 if (lowerInclusive) {
4584 if (lowerBound.compareTo(element) < 0) {
4585 throw new IllegalArgumentException("out of bounds");
4586 }
4587 } else {
4588 if (lowerBound.compareTo(element) <= 0) {
4589 throw new IllegalArgumentException("out of bounds");
4590 }
4591 }
4592 }
4593
4594 if (null != upperBound) {
4595 if (upperInclusive) {
4596 if (upperBound.compareTo(element) > 0) {
4597 throw new IllegalArgumentException("out of bounds");
4598 }
4599 } else {
4600 if (upperBound.compareTo(element) >= 0) {
4601 throw new IllegalArgumentException("out of bounds");
4602 }
4603 }
4604 }
4605 }
4606
4607 return (Comparable<E>) Objects.requireNonNull(element);
4608 }
4609
4610 @Override
4611 public EmptyNavigableSet<E> descendingSet() {
4612 if (upperBound == null && lowerBound == null && descending) {
4613 return (EmptyNavigableSet) Collections.emptyNavigableSet();
4614 }
4615 return new BoundedEmptyNavigableSet(
4616 upperBound, upperInclusive,
4617 lowerBound, lowerInclusive,
4618 !descending);
4619 }
4620
4621 @Override
4622 public BoundedEmptyNavigableSet<E> subSet(E fromKey, boolean fromInclusive, E toKey, boolean toInclusive) {
4623 return new BoundedEmptyNavigableSet(
4624 inBounds(fromKey), fromInclusive,
4625 inBounds(toKey), toInclusive,
4626 descending);
4627 }
4628
4629 @Override
4630 public BoundedEmptyNavigableSet<E> headSet(E toKey, boolean inclusive) {
4631 return new BoundedEmptyNavigableSet(
4632 lowerBound, lowerInclusive,
4633 inBounds(Objects.requireNonNull(toKey)), inclusive,
4634 descending);
4635 }
4636
4637 @Override
4638 public BoundedEmptyNavigableSet<E> tailSet(E fromKey, boolean inclusive) {
4639 return new BoundedEmptyNavigableSet(
4640 inBounds(Objects.requireNonNull(fromKey)), inclusive,
4641 upperBound, upperInclusive,
4642 descending);
4643 }
4644 }
4645
4646 /**
4647 * The empty map (immutable). This map is serializable.
4648 *
4649 * @see #emptyMap()
4650 * @since 1.3
4651 */
4652 @SuppressWarnings("rawtypes")
4653 public static final Map EMPTY_MAP = new EmptyMap<>();
4654
4655 /**
4656 * Returns the empty map (immutable). This map is serializable.
4657 *
4658 * <p>This example illustrates the type-safe way to obtain an empty map:
4659 * <pre>
4660 * Map<String, Date> s = Collections.emptyMap();
4661 * </pre>
4662 * @implNote Implementations of this method need not create a separate
4663 * {@code Map} object for each call. Using this method is likely to have
4664 * comparable cost to using the like-named field. (Unlike this method, the
4665 * field does not provide type safety.)
4666 *
4667 * @return an empty map
4668 * @see #EMPTY_MAP
4669 * @since 1.5
4670 */
4671 @SuppressWarnings("unchecked")
4672 public static final <K,V> Map<K,V> emptyMap() {
4673 return (Map<K,V>) EMPTY_MAP;
4674 }
4675
4676 /**
4677 * Returns an empty sorted map (immutable). This map is serializable.
4678 *
4679 * <p>This example illustrates the type-safe way to obtain an empty map:
4680 * <pre> {@code
4681 * SortedMap<String, Date> s = Collections.emptySortedMap();
4682 * }</pre>
4683 *
4684 * @implNote Implementations of this method need not create a separate
4685 * {@code SortedMap} object for each call.
4686 *
4687 * @return an empty sorted map
4688 * @since 1.8
4689 */
4690 @SuppressWarnings("unchecked")
4691 public static final <K,V> SortedMap<K,V> emptySortedMap() {
4692 return (SortedMap<K,V>) EmptyNavigableMap.EMPTY_NAVIGABLE_MAP;
4693 }
4694
4695 /**
4696 * Returns an empty navigable map (immutable). This map is serializable.
4697 *
4698 * <p>This example illustrates the type-safe way to obtain an empty map:
4699 * <pre> {@code
4700 * NavigableMap<String, Date> s = Collections.emptyNavigableMap();
4701 * }</pre>
4702 *
4703 * @implNote Implementations of this method need not create a separate
4704 * {@code NavigableMap} object for each call.
4705 *
4706 * @return an empty navigable map
4707 * @since 1.8
4708 */
4709 @SuppressWarnings("unchecked")
4710 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() {
4711 return (NavigableMap<K,V>) EmptyNavigableMap.EMPTY_NAVIGABLE_MAP;
4712 }
4713
4714 /**
4715 * @serial include
4716 */
4717 private static class EmptyMap<K,V>
4718 extends AbstractMap<K,V>
4719 implements Serializable
4720 {
4721 private static final long serialVersionUID = 6428348081105594320L;
4722
4723 public int size() {return 0;}
4724 public boolean isEmpty() {return true;}
4725 public boolean containsKey(Object key) {return false;}
4726 public boolean containsValue(Object value) {return false;}
4727 public V get(Object key) {return null;}
4728 public Set<K> keySet() {return emptySet();}
4729 public Collection<V> values() {return emptySet();}
4730 public Set<Map.Entry<K,V>> entrySet() {return emptySet();}
4731
4732 public boolean equals(Object o) {
4733 return (o instanceof Map) && ((Map<?,?>)o).isEmpty();
4734 }
4735
4736 public int hashCode() {return 0;}
4737
4738 // Override default methods in Map
4739 @Override
4740 @SuppressWarnings("unchecked")
4741 public V getOrDefault(Object k, V defaultValue) {
4742 return defaultValue;
4743 }
4744
4745 @Override
4746 public void forEach(BiConsumer<? super K, ? super V> action) {
4747 Objects.requireNonNull(action);
4748 }
4749
4750 @Override
4751 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4752 Objects.requireNonNull(function);
4753 }
4754
4755 @Override
4756 public V putIfAbsent(K key, V value) {
4757 throw new UnsupportedOperationException();
4758 }
4759
4760 @Override
4761 public boolean remove(Object key, Object value) {
4762 throw new UnsupportedOperationException();
4763 }
4764
4765 @Override
4766 public boolean replace(K key, V oldValue, V newValue) {
4767 throw new UnsupportedOperationException();
4768 }
4769
4770 @Override
4771 public V replace(K key, V value) {
4772 throw new UnsupportedOperationException();
4773 }
4774
4775 @Override
4776 public V computeIfAbsent(K key,
4777 Function<? super K, ? extends V> mappingFunction) {
4778 throw new UnsupportedOperationException();
4779 }
4780
4781 @Override
4782 public V computeIfPresent(K key,
4783 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4784 throw new UnsupportedOperationException();
4785 }
4786
4787 @Override
4788 public V compute(K key,
4789 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4790 throw new UnsupportedOperationException();
4791 }
4792
4793 @Override
4794 public V merge(K key, V value,
4795 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4796 throw new UnsupportedOperationException();
4797 }
4798
4799 // Preserves singleton property
4800 private Object readResolve() {
4801 return EMPTY_MAP;
4802 }
4803 }
4804
4805 /**
4806 * An empty navigable map.
4807 *
4808 * @param <K> type of keys, if there were any in this map
4809 * @param <V> type of values, if there were any in this map
4810 *
4811 * @serial include
4812 */
4813 private static class EmptyNavigableMap<K,V> extends EmptyMap<K,V>
4814 implements NavigableMap<K,V>, Serializable {
4815 private static final long serialVersionUID = -2239321462712562324L;
4816
4817 @SuppressWarnings("rawtypes")
4818 private static final NavigableMap EMPTY_NAVIGABLE_MAP =
4819 new EmptyNavigableMap();
4820
4821 EmptyNavigableMap() {}
4822
4823 @Override
4824 public boolean containsKey(Object obj) {
4825 Comparable<K> e = (Comparable<K>) Objects.requireNonNull(obj);
4826 return obj != e;
4827 }
4828
4829 // Preserves singleton property
4830 private Object readResolve() { return Collections.emptyNavigableMap();}
4831
4832 public final K firstKey() { throw new NoSuchElementException(); }
4833 public final K lastKey() { throw new NoSuchElementException(); }
4834
4835 public Entry<K, V> lowerEntry(K key) {
4836 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4837 return null;
4838 }
4839
4840 public K lowerKey(K key) {
4841 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4842 return null;
4843 }
4844
4845 public Entry<K, V> floorEntry(K key) {
4846 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4847 return null;
4848 }
4849
4850 public K floorKey(K key) {
4851 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4852 return null;
4853 }
4854
4855 public Entry<K, V> ceilingEntry(K key) {
4856 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4857 return null;
4858 }
4859
4860 public K ceilingKey(K key) {
4861 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4862 return null;
4863 }
4864
4865 public Entry<K, V> higherEntry(K key) {
4866 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4867 return null;
4868 }
4869
4870 public K higherKey(K key) {
4871 Comparable<K> k = (Comparable<K>) Objects.requireNonNull(key);
4872 return null;
4873 }
4874
4875 public Entry<K, V> firstEntry() { return null; }
4876 public Entry<K, V> lastEntry() { return null; }
4877 public Entry<K, V> pollFirstEntry()
4878 { throw new UnsupportedOperationException(); }
4879 public Entry<K, V> pollLastEntry()
4880 { throw new UnsupportedOperationException(); }
4881 public NavigableMap<K, V> descendingMap() {
4882 EmptyNavigableSet<K> descendingKeys = descendingKeySet();
4883
4884 if(descendingKeys == emptyNavigableSet()) {
4885 return emptyNavigableMap();
4886 } else {
4887 return new BoundedEmptyNavigableMap<>((BoundedEmptyNavigableSet<K>) descendingKeys);
4888 }
4889 }
4890
4891 public EmptyNavigableSet<K> navigableKeySet()
4892 { return (EmptyNavigableSet<K>) Collections.emptyNavigableSet(); }
4893 public EmptyNavigableSet<K> descendingKeySet() {
4894 return navigableKeySet().descendingSet();
4895 }
4896
4897 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
4898 return new BoundedEmptyNavigableMap<>(
4899 ((EmptyNavigableSet<K>) Collections.emptyNavigableSet()).subSet(
4900 fromKey, fromInclusive,
4901 toKey, toInclusive));
4902 }
4903
4904 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
4905 return new BoundedEmptyNavigableMap<>(
4906 ((EmptyNavigableSet<K>) Collections.emptyNavigableSet())
4907 .headSet(toKey, inclusive));
4908 }
4909
4910 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
4911 return new BoundedEmptyNavigableMap<>(
4912 ((EmptyNavigableSet<K>) Collections.emptyNavigableSet())
4913 .tailSet(fromKey, inclusive));
4914 }
4915
4916 public final SortedMap<K, V> subMap(K fromKey, K toKey)
4917 { return subMap(fromKey, true, toKey, false); }
4918
4919 public final SortedMap<K, V> headMap(K toKey)
4920 { return headMap(toKey, true); }
4921
4922 public final SortedMap<K, V> tailMap(K fromKey)
4923 { return tailMap(fromKey, false); }
4924
4925 public Comparator<? super K> comparator() { return null; }
4926 }
4927
4928 // Singleton collections
4929
4930 /**
4931 * Returns an immutable set containing only the specified object.
4932 * The returned set is serializable.
4933 *
4934 * @param o the sole object to be stored in the returned set.
4935 * @return an immutable set containing only the specified object.
4936 */
4937 public static <T> Set<T> singleton(T o) {
4938 return new SingletonSet<>(o);
4939 }
4940
4941 static <E> Iterator<E> singletonIterator(final E e) {
4942 return new Iterator<E>() {
4943 private boolean hasNext = true;
4944 public boolean hasNext() {
4945 return hasNext;
4946 }
4947 public E next() {
4948 if (hasNext) {
4949 hasNext = false;
4950 return e;
4951 }
4952 throw new NoSuchElementException();
4953 }
4954 public void remove() {
4955 throw new UnsupportedOperationException();
4956 }
4957 @Override
4958 public void forEachRemaining(Consumer<? super E> action) {
4959 Objects.requireNonNull(action);
4960 if (hasNext) {
4961 action.accept(e);
4962 hasNext = false;
4963 }
4964 }
4965 };
4966 }
4967
4968 /**
4969 * Creates a {@code Spliterator} with only the specified element
4970 *
4971 * @param <T> Type of elements
4972 * @return A singleton {@code Spliterator}
4973 */
4974 static <T> Spliterator<T> singletonSpliterator(final T element) {
4975 return new Spliterator<T>() {
4976 long est = 1;
4977
4978 @Override
4979 public Spliterator<T> trySplit() {
4980 return null;
4981 }
4982
4983 @Override
4984 public boolean tryAdvance(Consumer<? super T> consumer) {
4985 Objects.requireNonNull(consumer);
4986 if (est > 0) {
4987 est--;
4988 consumer.accept(element);
4989 return true;
4990 }
4991 return false;
4992 }
4993
4994 @Override
4995 public void forEachRemaining(Consumer<? super T> consumer) {
4996 tryAdvance(consumer);
4997 }
4998
4999 @Override
5000 public long estimateSize() {
5001 return est;
5002 }
5003
5004 @Override
5005 public int characteristics() {
5006 int value = (element != null) ? Spliterator.NONNULL : 0;
5007
5008 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE |
5009 Spliterator.DISTINCT | Spliterator.ORDERED;
5010 }
5011 };
5012 }
5013
5014 /**
5015 * @serial include
5016 */
5017 private static class SingletonSet<E>
5018 extends AbstractSet<E>
5019 implements Serializable
5020 {
5021 private static final long serialVersionUID = 3193687207550431679L;
5022
5023 private final E element;
5024
5025 SingletonSet(E e) {element = e;}
5026
5027 public Iterator<E> iterator() {
5028 return singletonIterator(element);
5029 }
5030
5031 public int size() {return 1;}
5032
5033 public boolean contains(Object o) {return eq(o, element);}
5034
5035 // Override default methods for Collection
5036 @Override
5037 public void forEach(Consumer<? super E> action) {
5038 action.accept(element);
5039 }
5040 @Override
5041 public Spliterator<E> spliterator() {
5042 return singletonSpliterator(element);
5043 }
5044 @Override
5045 public boolean removeIf(Predicate<? super E> filter) {
5046 throw new UnsupportedOperationException();
5047 }
5048 }
5049
5050 /**
5051 * Returns an immutable list containing only the specified object.
5052 * The returned list is serializable.
5053 *
5054 * @param o the sole object to be stored in the returned list.
5055 * @return an immutable list containing only the specified object.
5056 * @since 1.3
5057 */
5058 public static <T> List<T> singletonList(T o) {
5059 return new SingletonList<>(o);
5060 }
5061
5062 /**
5063 * @serial include
5064 */
5065 private static class SingletonList<E>
5066 extends AbstractList<E>
5067 implements RandomAccess, Serializable {
5068
5069 private static final long serialVersionUID = 3093736618740652951L;
5070
5071 private final E element;
5072
5073 SingletonList(E obj) {element = obj;}
5074
5075 public Iterator<E> iterator() {
5076 return singletonIterator(element);
5077 }
5078
5079 public int size() {return 1;}
5080
5081 public boolean contains(Object obj) {return eq(obj, element);}
5082
5083 public E get(int index) {
5084 if (index != 0)
5085 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
5086 return element;
5087 }
5088
5089 // Override default methods for Collection
5090 @Override
5091 public void forEach(Consumer<? super E> action) {
5092 action.accept(element);
5093 }
5094 @Override
5095 public boolean removeIf(Predicate<? super E> filter) {
5096 throw new UnsupportedOperationException();
5097 }
5098 @Override
5099 public void replaceAll(UnaryOperator<E> operator) {
5100 throw new UnsupportedOperationException();
5101 }
5102 @Override
5103 public void sort(Comparator<? super E> c) {
5104 }
5105 @Override
5106 public Spliterator<E> spliterator() {
5107 return singletonSpliterator(element);
5108 }
5109 }
5110
5111 /**
5112 * Returns an immutable map, mapping only the specified key to the
5113 * specified value. The returned map is serializable.
5114 *
5115 * @param key the sole key to be stored in the returned map.
5116 * @param value the value to which the returned map maps <tt>key</tt>.
5117 * @return an immutable map containing only the specified key-value
5118 * mapping.
5119 * @since 1.3
5120 */
5121 public static <K,V> Map<K,V> singletonMap(K key, V value) {
5122 return new SingletonMap<>(key, value);
5123 }
5124
5125 /**
5126 * @serial include
5127 */
5128 private static class SingletonMap<K,V>
5129 extends AbstractMap<K,V>
5130 implements Serializable {
5131 private static final long serialVersionUID = -6979724477215052911L;
5132
5133 private final K k;
5134 private final V v;
5135
5136 SingletonMap(K key, V value) {
5137 k = key;
5138 v = value;
5139 }
5140
5141 public int size() {return 1;}
5142 public boolean isEmpty() {return false;}
5143 public boolean containsKey(Object key) {return eq(key, k);}
5144 public boolean containsValue(Object value) {return eq(value, v);}
5145 public V get(Object key) {return (eq(key, k) ? v : null);}
5146
5147 private transient Set<K> keySet = null;
5148 private transient Set<Map.Entry<K,V>> entrySet = null;
5149 private transient Collection<V> values = null;
5150
5151 public Set<K> keySet() {
5152 if (keySet==null)
5153 keySet = singleton(k);
5154 return keySet;
5155 }
5156
5157 public Set<Map.Entry<K,V>> entrySet() {
5158 if (entrySet==null)
5159 entrySet = Collections.<Map.Entry<K,V>>singleton(
5160 new SimpleImmutableEntry<>(k, v));
5161 return entrySet;
5162 }
5163
5164 public Collection<V> values() {
5165 if (values==null)
5166 values = singleton(v);
5167 return values;
5168 }
5169
5170 // Override default methods in Map
5171 @Override
5172 public V getOrDefault(Object key, V defaultValue) {
5173 return eq(key, k) ? v : defaultValue;
5174 }
5175
5176 @Override
5177 public void forEach(BiConsumer<? super K, ? super V> action) {
5178 action.accept(k, v);
5179 }
5180
5181 @Override
5182 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
5183 throw new UnsupportedOperationException();
5184 }
5185
5186 @Override
5187 public V putIfAbsent(K key, V value) {
5188 throw new UnsupportedOperationException();
5189 }
5190
5191 @Override
5192 public boolean remove(Object key, Object value) {
5193 throw new UnsupportedOperationException();
5194 }
5195
5196 @Override
5197 public boolean replace(K key, V oldValue, V newValue) {
5198 throw new UnsupportedOperationException();
5199 }
5200
5201 @Override
5202 public V replace(K key, V value) {
5203 throw new UnsupportedOperationException();
5204 }
5205
5206 @Override
5207 public V computeIfAbsent(K key,
5208 Function<? super K, ? extends V> mappingFunction) {
5209 throw new UnsupportedOperationException();
5210 }
5211
5212 @Override
5213 public V computeIfPresent(K key,
5214 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
5215 throw new UnsupportedOperationException();
5216 }
5217
5218 @Override
5219 public V compute(K key,
5220 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
5221 throw new UnsupportedOperationException();
5222 }
5223
5224 @Override
5225 public V merge(K key, V value,
5226 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
5227 throw new UnsupportedOperationException();
5228 }
5229 }
5230
5231 // Miscellaneous
5232
5233 /**
5234 * Returns an immutable list consisting of <tt>n</tt> copies of the
5235 * specified object. The newly allocated data object is tiny (it contains
5236 * a single reference to the data object). This method is useful in
5237 * combination with the <tt>List.addAll</tt> method to grow lists.
5238 * The returned list is serializable.
5239 *
5240 * @param n the number of elements in the returned list.
5241 * @param o the element to appear repeatedly in the returned list.
5242 * @return an immutable list consisting of <tt>n</tt> copies of the
5243 * specified object.
5244 * @throws IllegalArgumentException if {@code n < 0}
5245 * @see List#addAll(Collection)
5246 * @see List#addAll(int, Collection)
5247 */
5248 public static <T> List<T> nCopies(int n, T o) {
5249 if (n < 0)
5250 throw new IllegalArgumentException("List length = " + n);
5251 return new CopiesList<>(n, o);
5252 }
5253
5254 /**
5255 * @serial include
5256 */
5257 private static class CopiesList<E>
5258 extends AbstractList<E>
5259 implements RandomAccess, Serializable
5260 {
5261 private static final long serialVersionUID = 2739099268398711800L;
5262
5263 final int n;
5264 final E element;
5265
5266 CopiesList(int n, E e) {
5267 assert n >= 0;
5268 this.n = n;
5269 element = e;
5270 }
5271
5272 public int size() {
5273 return n;
5274 }
5275
5276 public boolean contains(Object obj) {
5277 return n != 0 && eq(obj, element);
5278 }
5279
5280 public int indexOf(Object o) {
5281 return contains(o) ? 0 : -1;
5282 }
5283
5284 public int lastIndexOf(Object o) {
5285 return contains(o) ? n - 1 : -1;
5286 }
5287
5288 public E get(int index) {
5289 if (index < 0 || index >= n)
5290 throw new IndexOutOfBoundsException("Index: "+index+
5291 ", Size: "+n);
5292 return element;
5293 }
5294
5295 public Object[] toArray() {
5296 final Object[] a = new Object[n];
5297 if (element != null)
5298 Arrays.fill(a, 0, n, element);
5299 return a;
5300 }
5301
5302 @SuppressWarnings("unchecked")
5303 public <T> T[] toArray(T[] a) {
5304 final int n = this.n;
5305 if (a.length < n) {
5306 a = (T[])java.lang.reflect.Array
5307 .newInstance(a.getClass().getComponentType(), n);
5308 if (element != null)
5309 Arrays.fill(a, 0, n, element);
5310 } else {
5311 Arrays.fill(a, 0, n, element);
5312 if (a.length > n)
5313 a[n] = null;
5314 }
5315 return a;
5316 }
5317
5318 public List<E> subList(int fromIndex, int toIndex) {
5319 if (fromIndex < 0)
5320 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
5321 if (toIndex > n)
5322 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
5323 if (fromIndex > toIndex)
5324 throw new IllegalArgumentException("fromIndex(" + fromIndex +
5325 ") > toIndex(" + toIndex + ")");
5326 return new CopiesList<>(toIndex - fromIndex, element);
5327 }
5328 }
5329
5330 /**
5331 * Returns a comparator that imposes the reverse of the <em>natural
5332 * ordering</em> on a collection of objects that implement the
5333 * {@code Comparable} interface. (The natural ordering is the ordering
5334 * imposed by the objects' own {@code compareTo} method.) This enables a
5335 * simple idiom for sorting (or maintaining) collections (or arrays) of
5336 * objects that implement the {@code Comparable} interface in
5337 * reverse-natural-order. For example, suppose {@code a} is an array of
5338 * strings. Then: <pre>
5339 * Arrays.sort(a, Collections.reverseOrder());
5340 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
5341 *
5342 * The returned comparator is serializable.
5343 *
5344 * @return A comparator that imposes the reverse of the <i>natural
5345 * ordering</i> on a collection of objects that implement
5346 * the <tt>Comparable</tt> interface.
5347 * @see Comparable
5348 */
5349 @SuppressWarnings("unchecked")
5350 public static <T> Comparator<T> reverseOrder() {
5351 return (Comparator<T>) ReverseComparator.REVERSE_ORDER;
5352 }
5353
5354 /**
5355 * @serial include
5356 */
5357 private static class ReverseComparator
5358 implements Comparator<Comparable<Object>>, Serializable {
5359
5360 private static final long serialVersionUID = 7207038068494060240L;
5361
5362 static final ReverseComparator REVERSE_ORDER
5363 = new ReverseComparator();
5364
5365 public int compare(Comparable<Object> c1, Comparable<Object> c2) {
5366 return c2.compareTo(c1);
5367 }
5368
5369 private Object readResolve() { return Collections.reverseOrder(); }
5370 }
5371
5372 /**
5373 * Returns a comparator that imposes the reverse ordering of the specified
5374 * comparator. If the specified comparator is {@code null}, this method is
5375 * equivalent to {@link #reverseOrder()} (in other words, it returns a
5376 * comparator that imposes the reverse of the <em>natural ordering</em> on
5377 * a collection of objects that implement the Comparable interface).
5378 *
5379 * <p>The returned comparator is serializable (assuming the specified
5380 * comparator is also serializable or {@code null}).
5381 *
5382 * @param cmp a comparator who's ordering is to be reversed by the returned
5383 * comparator or {@code null}
5384 * @return A comparator that imposes the reverse ordering of the
5385 * specified comparator.
5386 * @since 1.5
5387 */
5388 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
5389 if (cmp == null)
5390 return reverseOrder();
5391
5392 if (cmp instanceof ReverseComparator2)
5393 return ((ReverseComparator2<T>)cmp).cmp;
5394
5395 return new ReverseComparator2<>(cmp);
5396 }
5397
5398 /**
5399 * @serial include
5400 */
5401 private static class ReverseComparator2<T> implements Comparator<T>,
5402 Serializable
5403 {
5404 private static final long serialVersionUID = 4374092139857L;
5405
5406 /**
5407 * The comparator specified in the static factory. This will never
5408 * be null, as the static factory returns a ReverseComparator
5409 * instance if its argument is null.
5410 *
5411 * @serial
5412 */
5413 final Comparator<T> cmp;
5414
5415 ReverseComparator2(Comparator<T> cmp) {
5416 assert cmp != null;
5417 this.cmp = cmp;
5418 }
5419
5420 public int compare(T t1, T t2) {
5421 return cmp.compare(t2, t1);
5422 }
5423
5424 public boolean equals(Object o) {
5425 return (o == this) ||
5426 (o instanceof ReverseComparator2 &&
5427 cmp.equals(((ReverseComparator2)o).cmp));
5428 }
5429
5430 public int hashCode() {
5431 return cmp.hashCode() ^ Integer.MIN_VALUE;
5432 }
5433 }
5434
5435 /**
5436 * Returns an enumeration over the specified collection. This provides
5437 * interoperability with legacy APIs that require an enumeration
5438 * as input.
5439 *
5440 * @param c the collection for which an enumeration is to be returned.
5441 * @return an enumeration over the specified collection.
5442 * @see Enumeration
5443 */
5444 public static <T> Enumeration<T> enumeration(final Collection<T> c) {
5445 return new Enumeration<T>() {
5446 private final Iterator<T> i = c.iterator();
5447
5448 public boolean hasMoreElements() {
5449 return i.hasNext();
5450 }
5451
5452 public T nextElement() {
5453 return i.next();
5454 }
5455 };
5456 }
5457
5458 /**
5459 * Returns an array list containing the elements returned by the
5460 * specified enumeration in the order they are returned by the
5461 * enumeration. This method provides interoperability between
5462 * legacy APIs that return enumerations and new APIs that require
5463 * collections.
5464 *
5465 * @param e enumeration providing elements for the returned
5466 * array list
5467 * @return an array list containing the elements returned
5468 * by the specified enumeration.
5469 * @since 1.4
5470 * @see Enumeration
5471 * @see ArrayList
5472 */
5473 public static <T> ArrayList<T> list(Enumeration<T> e) {
5474 ArrayList<T> l = new ArrayList<>();
5475 while (e.hasMoreElements())
5476 l.add(e.nextElement());
5477 return l;
5478 }
5479
5480 /**
5481 * Returns true if the specified arguments are equal, or both null.
5482 */
5483 static boolean eq(Object o1, Object o2) {
5484 return o1==null ? o2==null : o1.equals(o2);
5485 }
5486
5487 /**
5488 * Returns the number of elements in the specified collection equal to the
5489 * specified object. More formally, returns the number of elements
5490 * <tt>e</tt> in the collection such that
5491 * <tt>(o == null ? e == null : o.equals(e))</tt>.
5492 *
5493 * @param c the collection in which to determine the frequency
5494 * of <tt>o</tt>
5495 * @param o the object whose frequency is to be determined
5496 * @throws NullPointerException if <tt>c</tt> is null
5497 * @since 1.5
5498 */
5499 public static int frequency(Collection<?> c, Object o) {
5500 int result = 0;
5501 if (o == null) {
5502 for (Object e : c)
5503 if (e == null)
5504 result++;
5505 } else {
5506 for (Object e : c)
5507 if (o.equals(e))
5508 result++;
5509 }
5510 return result;
5511 }
5512
5513 /**
5514 * Returns {@code true} if the two specified collections have no
5515 * elements in common.
5516 *
5517 * <p>Care must be exercised if this method is used on collections that
5518 * do not comply with the general contract for {@code Collection}.
5519 * Implementations may elect to iterate over either collection and test
5520 * for containment in the other collection (or to perform any equivalent
5521 * computation). If either collection uses a nonstandard equality test
5522 * (as does a {@link SortedSet} whose ordering is not <em>compatible with
5523 * equals</em>, or the key set of an {@link IdentityHashMap}), both
5524 * collections must use the same nonstandard equality test, or the
5525 * result of this method is undefined.
5526 *
5527 * <p>Care must also be exercised when using collections that have
5528 * restrictions on the elements that they may contain. Collection
5529 * implementations are allowed to throw exceptions for any operation
5530 * involving elements they deem ineligible. For absolute safety the
5531 * specified collections should contain only elements which are
5532 * eligible elements for both collections.
5533 *
5534 * <p>Note that it is permissible to pass the same collection in both
5535 * parameters, in which case the method will return {@code true} if and
5536 * only if the collection is empty.
5537 *
5538 * @param c1 a collection
5539 * @param c2 a collection
5540 * @return {@code true} if the two specified collections have no
5541 * elements in common.
5542 * @throws NullPointerException if either collection is {@code null}.
5543 * @throws NullPointerException if one collection contains a {@code null}
5544 * element and {@code null} is not an eligible element for the other collection.
5545 * (<a href="Collection.html#optional-restrictions">optional</a>)
5546 * @throws ClassCastException if one collection contains an element that is
5547 * of a type which is ineligible for the other collection.
5548 * (<a href="Collection.html#optional-restrictions">optional</a>)
5549 * @since 1.5
5550 */
5551 public static boolean disjoint(Collection<?> c1, Collection<?> c2) {
5552 // The collection to be used for contains(). Preference is given to
5553 // the collection who's contains() has lower O() complexity.
5554 Collection<?> contains = c2;
5555 // The collection to be iterated. If the collections' contains() impl
5556 // are of different O() complexity, the collection with slower
5557 // contains() will be used for iteration. For collections who's
5558 // contains() are of the same complexity then best performance is
5559 // achieved by iterating the smaller collection.
5560 Collection<?> iterate = c1;
5561
5562 // Performance optimization cases. The heuristics:
5563 // 1. Generally iterate over c1.
5564 // 2. If c1 is a Set then iterate over c2.
5565 // 3. If either collection is empty then result is always true.
5566 // 4. Iterate over the smaller Collection.
5567 if (c1 instanceof Set) {
5568 // Use c1 for contains as a Set's contains() is expected to perform
5569 // better than O(N/2)
5570 iterate = c2;
5571 contains = c1;
5572 } else if (!(c2 instanceof Set)) {
5573 // Both are mere Collections. Iterate over smaller collection.
5574 // Example: If c1 contains 3 elements and c2 contains 50 elements and
5575 // assuming contains() requires ceiling(N/2) comparisons then
5576 // checking for all c1 elements in c2 would require 75 comparisons
5577 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring
5578 // 100 comparisons (50 * ceiling(3/2)).
5579 int c1size = c1.size();
5580 int c2size = c2.size();
5581 if (c1size == 0 || c2size == 0) {
5582 // At least one collection is empty. Nothing will match.
5583 return true;
5584 }
5585
5586 if (c1size > c2size) {
5587 iterate = c2;
5588 contains = c1;
5589 }
5590 }
5591
5592 for (Object e : iterate) {
5593 if (contains.contains(e)) {
5594 // Found a common element. Collections are not disjoint.
5595 return false;
5596 }
5597 }
5598
5599 // No common elements were found.
5600 return true;
5601 }
5602
5603 /**
5604 * Adds all of the specified elements to the specified collection.
5605 * Elements to be added may be specified individually or as an array.
5606 * The behavior of this convenience method is identical to that of
5607 * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely
5608 * to run significantly faster under most implementations.
5609 *
5610 * <p>When elements are specified individually, this method provides a
5611 * convenient way to add a few elements to an existing collection:
5612 * <pre>
5613 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
5614 * </pre>
5615 *
5616 * @param c the collection into which <tt>elements</tt> are to be inserted
5617 * @param elements the elements to insert into <tt>c</tt>
5618 * @return <tt>true</tt> if the collection changed as a result of the call
5619 * @throws UnsupportedOperationException if <tt>c</tt> does not support
5620 * the <tt>add</tt> operation
5621 * @throws NullPointerException if <tt>elements</tt> contains one or more
5622 * null values and <tt>c</tt> does not permit null elements, or
5623 * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt>
5624 * @throws IllegalArgumentException if some property of a value in
5625 * <tt>elements</tt> prevents it from being added to <tt>c</tt>
5626 * @see Collection#addAll(Collection)
5627 * @since 1.5
5628 */
5629 @SafeVarargs
5630 public static <T> boolean addAll(Collection<? super T> c, T... elements) {
5631 boolean result = false;
5632 for (T element : elements)
5633 result |= c.add(element);
5634 return result;
5635 }
5636
5637 /**
5638 * Returns a set backed by the specified map. The resulting set displays
5639 * the same ordering, concurrency, and performance characteristics as the
5640 * backing map. In essence, this factory method provides a {@link Set}
5641 * implementation corresponding to any {@link Map} implementation. There
5642 * is no need to use this method on a {@link Map} implementation that
5643 * already has a corresponding {@link Set} implementation (such as {@link
5644 * HashMap} or {@link TreeMap}).
5645 *
5646 * <p>Each method invocation on the set returned by this method results in
5647 * exactly one method invocation on the backing map or its <tt>keySet</tt>
5648 * view, with one exception. The <tt>addAll</tt> method is implemented
5649 * as a sequence of <tt>put</tt> invocations on the backing map.
5650 *
5651 * <p>The specified map must be empty at the time this method is invoked,
5652 * and should not be accessed directly after this method returns. These
5653 * conditions are ensured if the map is created empty, passed directly
5654 * to this method, and no reference to the map is retained, as illustrated
5655 * in the following code fragment:
5656 * <pre>
5657 * Set<Object> weakHashSet = Collections.newSetFromMap(
5658 * new WeakHashMap<Object, Boolean>());
5659 * </pre>
5660 *
5661 * @param map the backing map
5662 * @return the set backed by the map
5663 * @throws IllegalArgumentException if <tt>map</tt> is not empty
5664 * @since 1.6
5665 */
5666 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
5667 return new SetFromMap<>(map);
5668 }
5669
5670 /**
5671 * @serial include
5672 */
5673 private static class SetFromMap<E> extends AbstractSet<E>
5674 implements Set<E>, Serializable
5675 {
5676 private final Map<E, Boolean> m; // The backing map
5677 private transient Set<E> s; // Its keySet
5678
5679 SetFromMap(Map<E, Boolean> map) {
5680 if (!map.isEmpty())
5681 throw new IllegalArgumentException("Map is non-empty");
5682 m = map;
5683 s = map.keySet();
5684 }
5685
5686 public void clear() { m.clear(); }
5687 public int size() { return m.size(); }
5688 public boolean isEmpty() { return m.isEmpty(); }
5689 public boolean contains(Object o) { return m.containsKey(o); }
5690 public boolean remove(Object o) { return m.remove(o) != null; }
5691 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
5692 public Iterator<E> iterator() { return s.iterator(); }
5693 public Object[] toArray() { return s.toArray(); }
5694 public <T> T[] toArray(T[] a) { return s.toArray(a); }
5695 public String toString() { return s.toString(); }
5696 public int hashCode() { return s.hashCode(); }
5697 public boolean equals(Object o) { return o == this || s.equals(o); }
5698 public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
5699 public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
5700 public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
5701 // addAll is the only inherited implementation
5702
5703 // Override default methods in Collection
5704 @Override
5705 public void forEach(Consumer<? super E> action) {
5706 s.forEach(action);
5707 }
5708 @Override
5709 public boolean removeIf(Predicate<? super E> filter) {
5710 return s.removeIf(filter);
5711 }
5712
5713 @Override
5714 public Spliterator<E> spliterator() {return s.spliterator();}
5715
5716 private static final long serialVersionUID = 2454657854757543876L;
5717
5718 private void readObject(java.io.ObjectInputStream stream)
5719 throws IOException, ClassNotFoundException
5720 {
5721 stream.defaultReadObject();
5722 s = m.keySet();
5723 }
5724 }
5725
5726 /**
5727 * Returns a navigable set backed by the specified map. The resulting
5728 * navigable set displays the same ordering, concurrency, and performance
5729 * characteristics as the backing map. In essence, this factory method
5730 * provides a {@link NavigableSet} implementation corresponding to any
5731 * {@link NavigableMap} implementation. There is no need to use this method
5732 * on a {@link NavigableMap} implementation that already has a corresponding
5733 * {@link Set} implementation (such as {@link TreeMap}).
5734 *
5735 * <p>Each method invocation on the set returned by this method results in
5736 * exactly one method invocation on the backing map or its {@code keySet}
5737 * view, with one exception. The {@code addAll} method is implemented
5738 * as a sequence of {@code put} invocations on the backing map.
5739 *
5740 * <p>The specified map must be empty at the time this method is invoked,
5741 * and should not be accessed directly after this method returns. These
5742 * conditions are ensured if the map is created empty, passed directly
5743 * to this method, and no reference to the map is retained, as illustrated
5744 * in the following code fragment:
5745 * <pre> {@code
5746 * Set<Object> weakHashSet = Collections.newNavigableSetFromNavigableMap(
5747 * new WeakHashMap<Object, Boolean>());
5748 * }</pre>
5749 *
5750 * @param map the backing navigable map
5751 * @return the navigable set backed by the map
5752 * @throws IllegalArgumentException if {@code map} is not empty
5753 * @since 1.8
5754 */
5755 public static <E> NavigableSet<E> newNavigableSetFromNavigableMap(NavigableMap<E, Boolean> map) {
5756 return new NavigableSetFromNavigableMap<>(map);
5757 }
5758
5759 /**
5760 * @serial include
5761 */
5762 private static class NavigableSetFromNavigableMap<E> extends AbstractSet<E>
5763 implements NavigableSet<E>, Serializable
5764 {
5765 private static final long serialVersionUID = -7303807726339382839L;
5766
5767 private final NavigableMap<E, Boolean> m; // The backing map
5768 private transient NavigableSet<E> s; // Its keySet
5769
5770 NavigableSetFromNavigableMap(NavigableMap<E, Boolean> map) {
5771 if (!map.isEmpty())
5772 throw new IllegalArgumentException("Map is non-empty");
5773 m = map;
5774 s = map.navigableKeySet();
5775 }
5776
5777 public void clear() { m.clear(); }
5778 public int size() { return m.size(); }
5779 public boolean isEmpty() { return m.isEmpty(); }
5780 public boolean contains(Object o) { return m.containsKey(o); }
5781 public boolean remove(Object o) { return m.remove(o) != null; }
5782 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
5783 public Iterator<E> iterator() { return s.iterator(); }
5784 public Object[] toArray() { return s.toArray(); }
5785 public <T> T[] toArray(T[] a) { return s.toArray(a); }
5786 public String toString() { return s.toString(); }
5787 public int hashCode() { return s.hashCode(); }
5788 public boolean equals(Object o) { return o == this || s.equals(o); }
5789 public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
5790 public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
5791 public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
5792 // addAll is the only inherited implementation
5793
5794 // Override default methods in Collection
5795 @Override
5796 public void forEach(Consumer<? super E> action) { s.forEach(action); }
5797 @Override
5798 public boolean removeIf(Predicate<? super E> filter) {
5799 return s.removeIf(filter);
5800 }
5801
5802 @Override
5803 public Spliterator<E> spliterator() {return s.spliterator();}
5804
5805 private void readObject(java.io.ObjectInputStream stream)
5806 throws IOException, ClassNotFoundException {
5807 stream.defaultReadObject();
5808 if (null == m) {
5809 throw new InvalidObjectException("null map");
5810 }
5811 s = m.navigableKeySet();
5812 }
5813
5814 public E lower(E e) { return m.lowerKey(e); }
5815 public E floor(E e) { return m.floorKey(e); }
5816 public E ceiling(E e) { return m.ceilingKey(e); }
5817 public E higher(E e) { return m.higherKey(e); }
5818 public E pollFirst() { return s.pollFirst(); }
5819 public E pollLast() { return s.pollLast(); }
5820 public NavigableSet<E> descendingSet() { return s.descendingSet(); }
5821 public Iterator<E> descendingIterator(){return s.descendingIterator();}
5822
5823 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
5824 return s.subSet(fromElement, fromInclusive, toElement, toInclusive);
5825 }
5826
5827 public NavigableSet<E> headSet(E toElement, boolean inclusive)
5828 { return s.headSet(toElement, inclusive); }
5829 public NavigableSet<E> tailSet(E fromElement, boolean inclusive)
5830 { return s.tailSet(fromElement, inclusive); }
5831 public SortedSet<E> subSet(E fromElement, E toElement)
5832 { return s.subSet(fromElement, toElement); }
5833 public SortedSet<E> headSet(E toElement)
5834 { return s.headSet(toElement); }
5835 public SortedSet<E> tailSet(E fromElement)
5836 { return s.tailSet(fromElement); }
5837 public Comparator<? super E> comparator() { return s.comparator(); }
5838 public E first() { return s.first(); }
5839 public E last() { return s.last(); }
5840 }
5841
5842 /**
5843 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
5844 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>,
5845 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This
5846 * view can be useful when you would like to use a method
5847 * requiring a <tt>Queue</tt> but you need Lifo ordering.
5848 *
5849 * <p>Each method invocation on the queue returned by this method
5850 * results in exactly one method invocation on the backing deque, with
5851 * one exception. The {@link Queue#addAll addAll} method is
5852 * implemented as a sequence of {@link Deque#addFirst addFirst}
5853 * invocations on the backing deque.
5854 *
5855 * @param deque the deque
5856 * @return the queue
5857 * @since 1.6
5858 */
5859 public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
5860 return new AsLIFOQueue<>(deque);
5861 }
5862
5863 /**
5864 * @serial include
5865 */
5866 static class AsLIFOQueue<E> extends AbstractQueue<E>
5867 implements Queue<E>, Serializable {
5868 private static final long serialVersionUID = 1802017725587941708L;
5869 private final Deque<E> q;
5870 AsLIFOQueue(Deque<E> q) { this.q = q; }
5871 public boolean add(E e) { q.addFirst(e); return true; }
5872 public boolean offer(E e) { return q.offerFirst(e); }
5873 public E poll() { return q.pollFirst(); }
5874 public E remove() { return q.removeFirst(); }
5875 public E peek() { return q.peekFirst(); }
5876 public E element() { return q.getFirst(); }
5877 public void clear() { q.clear(); }
5878 public int size() { return q.size(); }
5879 public boolean isEmpty() { return q.isEmpty(); }
5880 public boolean contains(Object o) { return q.contains(o); }
5881 public boolean remove(Object o) { return q.remove(o); }
5882 public Iterator<E> iterator() { return q.iterator(); }
5883 public Object[] toArray() { return q.toArray(); }
5884 public <T> T[] toArray(T[] a) { return q.toArray(a); }
5885 public String toString() { return q.toString(); }
5886 public boolean containsAll(Collection<?> c) {return q.containsAll(c);}
5887 public boolean removeAll(Collection<?> c) {return q.removeAll(c);}
5888 public boolean retainAll(Collection<?> c) {return q.retainAll(c);}
5889 // We use inherited addAll; forwarding addAll would be wrong
5890
5891 // Override default methods in Collection
5892 @Override
5893 public void forEach(Consumer<? super E> action) {q.forEach(action);}
5894 @Override
5895 public Spliterator<E> spliterator() {return q.spliterator();}
5896 @Override
5897 public boolean removeIf(Predicate<? super E> filter) {
5898 return q.removeIf(filter);
5899 }
5900 }
5901 }