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 import java.util.stream.Stream;
39 import java.util.stream.StreamSupport;
40
41 /**
42 * This class consists exclusively of static methods that operate on or return
43 * collections. It contains polymorphic algorithms that operate on
44 * collections, "wrappers", which return a new collection backed by a
45 * specified collection, and a few other odds and ends.
46 *
47 * <p>The methods of this class all throw a <tt>NullPointerException</tt>
48 * if the collections or class objects provided to them are null.
49 *
50 * <p>The documentation for the polymorphic algorithms contained in this class
51 * generally includes a brief description of the <i>implementation</i>. Such
52 * descriptions should be regarded as <i>implementation notes</i>, rather than
53 * parts of the <i>specification</i>. Implementors should feel free to
54 * substitute other algorithms, so long as the specification itself is adhered
55 * to. (For example, the algorithm used by <tt>sort</tt> does not have to be
56 * a mergesort, but it does have to be <i>stable</i>.)
57 *
58 * <p>The "destructive" algorithms contained in this class, that is, the
59 * algorithms that modify the collection on which they operate, are specified
60 * to throw <tt>UnsupportedOperationException</tt> if the collection does not
61 * support the appropriate mutation primitive(s), such as the <tt>set</tt>
62 * method. These algorithms may, but are not required to, throw this
63 * exception if an invocation would have no effect on the collection. For
64 * example, invoking the <tt>sort</tt> method on an unmodifiable list that is
65 * already sorted may or may not throw <tt>UnsupportedOperationException</tt>.
66 *
67 * <p>This class is a member of the
68 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
69 * Java Collections Framework</a>.
70 *
71 * @author Josh Bloch
72 * @author Neal Gafter
73 * @see Collection
74 * @see Set
75 * @see List
76 * @see Map
77 * @since 1.2
78 */
79
80 public class Collections {
81 // Suppresses default constructor, ensuring non-instantiability.
82 private Collections() {
83 }
84
85 // Algorithms
86
87 /*
88 * Tuning parameters for algorithms - Many of the List algorithms have
89 * two implementations, one of which is appropriate for RandomAccess
90 * lists, the other for "sequential." Often, the random access variant
91 * yields better performance on small sequential access lists. The
92 * tuning parameters below determine the cutoff point for what constitutes
93 * a "small" sequential access list for each algorithm. The values below
94 * were empirically determined to work well for LinkedList. Hopefully
95 * they should be reasonable for other sequential access List
96 * implementations. Those doing performance work on this code would
97 * do well to validate the values of these parameters from time to time.
98 * (The first word of each tuning parameter name is the algorithm to which
99 * it applies.)
100 */
101 private static final int BINARYSEARCH_THRESHOLD = 5000;
102 private static final int REVERSE_THRESHOLD = 18;
103 private static final int SHUFFLE_THRESHOLD = 5;
104 private static final int FILL_THRESHOLD = 25;
105 private static final int ROTATE_THRESHOLD = 100;
106 private static final int COPY_THRESHOLD = 10;
107 private static final int REPLACEALL_THRESHOLD = 11;
108 private static final int INDEXOFSUBLIST_THRESHOLD = 35;
109
110 /**
111 * Sorts the specified list into ascending order, according to the
112 * {@linkplain Comparable natural ordering} of its elements.
113 * All elements in the list must implement the {@link Comparable}
114 * interface. Furthermore, all elements in the list must be
115 * <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)}
116 * must not throw a {@code ClassCastException} for any elements
117 * {@code e1} and {@code e2} in the list).
118 *
119 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will
120 * not be reordered as a result of the sort.
121 *
122 * <p>The specified list must be modifiable, but need not be resizable.
123 *
124 * <p>Implementation note: This implementation is a stable, adaptive,
125 * iterative mergesort that requires far fewer than n lg(n) comparisons
126 * when the input array is partially sorted, while offering the
127 * performance of a traditional mergesort when the input array is
128 * randomly ordered. If the input array is nearly sorted, the
129 * implementation requires approximately n comparisons. Temporary
130 * storage requirements vary from a small constant for nearly sorted
131 * input arrays to n/2 object references for randomly ordered input
132 * arrays.
133 *
134 * <p>The implementation takes equal advantage of ascending and
135 * descending order in its input array, and can take advantage of
136 * ascending and descending order in different parts of the same
137 * input array. It is well-suited to merging two or more sorted arrays:
138 * simply concatenate the arrays and sort the resulting array.
139 *
140 * <p>The implementation was adapted from Tim Peters's list sort for Python
141 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
142 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
143 * Sorting and Information Theoretic Complexity", in Proceedings of the
144 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
145 * January 1993.
146 *
147 * <p>This implementation dumps the specified list into an array, sorts
148 * the array, and iterates over the list resetting each element
149 * from the corresponding position in the array. This avoids the
150 * n<sup>2</sup> log(n) performance that would result from attempting
151 * to sort a linked list in place.
152 *
153 * @param <T> the class of the objects in the list
154 * @param list the list to be sorted.
155 * @throws ClassCastException if the list contains elements that are not
156 * <i>mutually comparable</i> (for example, strings and integers).
157 * @throws UnsupportedOperationException if the specified list's
158 * list-iterator does not support the {@code set} operation.
159 * @throws IllegalArgumentException (optional) if the implementation
160 * detects that the natural ordering of the list elements is
161 * found to violate the {@link Comparable} contract
162 */
163 @SuppressWarnings("unchecked")
164 public static <T extends Comparable<? super T>> void sort(List<T> list) {
165 Object[] a = list.toArray();
166 Arrays.sort(a);
167 ListIterator<T> i = list.listIterator();
168 for (int j=0; j<a.length; j++) {
169 i.next();
170 i.set((T)a[j]);
171 }
172 }
173
174 /**
175 * Sorts the specified list according to the order induced by the
176 * specified comparator. All elements in the list must be <i>mutually
177 * comparable</i> using the specified comparator (that is,
178 * {@code c.compare(e1, e2)} must not throw a {@code ClassCastException}
179 * for any elements {@code e1} and {@code e2} in the list).
180 *
181 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will
182 * not be reordered as a result of the sort.
183 *
184 * <p>The specified list must be modifiable, but need not be resizable.
185 *
186 * <p>Implementation note: This implementation is a stable, adaptive,
187 * iterative mergesort that requires far fewer than n lg(n) comparisons
188 * when the input array is partially sorted, while offering the
189 * performance of a traditional mergesort when the input array is
190 * randomly ordered. If the input array is nearly sorted, the
191 * implementation requires approximately n comparisons. Temporary
192 * storage requirements vary from a small constant for nearly sorted
193 * input arrays to n/2 object references for randomly ordered input
194 * arrays.
195 *
196 * <p>The implementation takes equal advantage of ascending and
197 * descending order in its input array, and can take advantage of
198 * ascending and descending order in different parts of the same
199 * input array. It is well-suited to merging two or more sorted arrays:
200 * simply concatenate the arrays and sort the resulting array.
201 *
202 * <p>The implementation was adapted from Tim Peters's list sort for Python
203 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
204 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
205 * Sorting and Information Theoretic Complexity", in Proceedings of the
206 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
207 * January 1993.
208 *
209 * <p>This implementation dumps the specified list into an array, sorts
210 * the array, and iterates over the list resetting each element
211 * from the corresponding position in the array. This avoids the
212 * n<sup>2</sup> log(n) performance that would result from attempting
213 * to sort a linked list in place.
214 *
215 * @param <T> the class of the objects in the list
216 * @param list the list to be sorted.
217 * @param c the comparator to determine the order of the list. A
218 * {@code null} value indicates that the elements' <i>natural
219 * ordering</i> should be used.
220 * @throws ClassCastException if the list contains elements that are not
221 * <i>mutually comparable</i> using the specified comparator.
222 * @throws UnsupportedOperationException if the specified list's
223 * list-iterator does not support the {@code set} operation.
224 * @throws IllegalArgumentException (optional) if the comparator is
225 * found to violate the {@link Comparator} contract
226 */
227 @SuppressWarnings({"unchecked", "rawtypes"})
228 public static <T> void sort(List<T> list, Comparator<? super T> c) {
229 Object[] a = list.toArray();
230 Arrays.sort(a, (Comparator)c);
231 ListIterator<T> i = list.listIterator();
232 for (int j=0; j<a.length; j++) {
233 i.next();
234 i.set((T)a[j]);
235 }
236 }
237
238
239 /**
240 * Searches the specified list for the specified object using the binary
241 * search algorithm. The list must be sorted into ascending order
242 * according to the {@linkplain Comparable natural ordering} of its
243 * elements (as by the {@link #sort(List)} method) prior to making this
244 * call. If it is not sorted, the results are undefined. If the list
245 * contains multiple elements equal to the specified object, there is no
246 * guarantee which one will be found.
247 *
248 * <p>This method runs in log(n) time for a "random access" list (which
249 * provides near-constant-time positional access). If the specified list
250 * does not implement the {@link RandomAccess} interface and is large,
251 * this method will do an iterator-based binary search that performs
252 * O(n) link traversals and O(log n) element comparisons.
253 *
254 * @param <T> the class of the objects in the list
255 * @param list the list to be searched.
256 * @param key the key to be searched for.
257 * @return the index of the search key, if it is contained in the list;
258 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
259 * <i>insertion point</i> is defined as the point at which the
260 * key would be inserted into the list: the index of the first
261 * element greater than the key, or <tt>list.size()</tt> if all
262 * elements in the list are less than the specified key. Note
263 * that this guarantees that the return value will be >= 0 if
264 * and only if the key is found.
265 * @throws ClassCastException if the list contains elements that are not
266 * <i>mutually comparable</i> (for example, strings and
267 * integers), or the search key is not mutually comparable
268 * with the elements of the list.
269 */
270 public static <T>
271 int binarySearch(List<? extends Comparable<? super T>> list, T key) {
272 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
273 return Collections.indexedBinarySearch(list, key);
274 else
275 return Collections.iteratorBinarySearch(list, key);
276 }
277
278 private static <T>
279 int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) {
280 int low = 0;
281 int high = list.size()-1;
282
283 while (low <= high) {
284 int mid = (low + high) >>> 1;
285 Comparable<? super T> midVal = list.get(mid);
286 int cmp = midVal.compareTo(key);
287
288 if (cmp < 0)
289 low = mid + 1;
290 else if (cmp > 0)
291 high = mid - 1;
292 else
293 return mid; // key found
294 }
295 return -(low + 1); // key not found
296 }
297
298 private static <T>
299 int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
300 {
301 int low = 0;
302 int high = list.size()-1;
303 ListIterator<? extends Comparable<? super T>> i = list.listIterator();
304
305 while (low <= high) {
306 int mid = (low + high) >>> 1;
307 Comparable<? super T> midVal = get(i, mid);
308 int cmp = midVal.compareTo(key);
309
310 if (cmp < 0)
311 low = mid + 1;
312 else if (cmp > 0)
313 high = mid - 1;
314 else
315 return mid; // key found
316 }
317 return -(low + 1); // key not found
318 }
319
320 /**
321 * Gets the ith element from the given list by repositioning the specified
322 * list listIterator.
323 */
324 private static <T> T get(ListIterator<? extends T> i, int index) {
325 T obj = null;
326 int pos = i.nextIndex();
327 if (pos <= index) {
328 do {
329 obj = i.next();
330 } while (pos++ < index);
331 } else {
332 do {
333 obj = i.previous();
334 } while (--pos > index);
335 }
336 return obj;
337 }
338
339 /**
340 * Searches the specified list for the specified object using the binary
341 * search algorithm. The list must be sorted into ascending order
342 * according to the specified comparator (as by the
343 * {@link #sort(List, Comparator) sort(List, Comparator)}
344 * method), prior to making this call. If it is
345 * not sorted, the results are undefined. If the list contains multiple
346 * elements equal to the specified object, there is no guarantee which one
347 * will be found.
348 *
349 * <p>This method runs in log(n) time for a "random access" list (which
350 * provides near-constant-time positional access). If the specified list
351 * does not implement the {@link RandomAccess} interface and is large,
352 * this method will do an iterator-based binary search that performs
353 * O(n) link traversals and O(log n) element comparisons.
354 *
355 * @param <T> the class of the objects in the list
356 * @param list the list to be searched.
357 * @param key the key to be searched for.
358 * @param c the comparator by which the list is ordered.
359 * A <tt>null</tt> value indicates that the elements'
360 * {@linkplain Comparable natural ordering} should be used.
361 * @return the index of the search key, if it is contained in the list;
362 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
363 * <i>insertion point</i> is defined as the point at which the
364 * key would be inserted into the list: the index of the first
365 * element greater than the key, or <tt>list.size()</tt> if all
366 * elements in the list are less than the specified key. Note
367 * that this guarantees that the return value will be >= 0 if
368 * and only if the key is found.
369 * @throws ClassCastException if the list contains elements that are not
370 * <i>mutually comparable</i> using the specified comparator,
371 * or the search key is not mutually comparable with the
372 * elements of the list using this comparator.
373 */
374 @SuppressWarnings("unchecked")
375 public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
376 if (c==null)
377 return binarySearch((List<? extends Comparable<? super T>>) list, key);
378
379 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
380 return Collections.indexedBinarySearch(list, key, c);
381 else
382 return Collections.iteratorBinarySearch(list, key, c);
383 }
384
385 private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
386 int low = 0;
387 int high = l.size()-1;
388
389 while (low <= high) {
390 int mid = (low + high) >>> 1;
391 T midVal = l.get(mid);
392 int cmp = c.compare(midVal, key);
393
394 if (cmp < 0)
395 low = mid + 1;
396 else if (cmp > 0)
397 high = mid - 1;
398 else
399 return mid; // key found
400 }
401 return -(low + 1); // key not found
402 }
403
404 private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
405 int low = 0;
406 int high = l.size()-1;
407 ListIterator<? extends T> i = l.listIterator();
408
409 while (low <= high) {
410 int mid = (low + high) >>> 1;
411 T midVal = get(i, mid);
412 int cmp = c.compare(midVal, key);
413
414 if (cmp < 0)
415 low = mid + 1;
416 else if (cmp > 0)
417 high = mid - 1;
418 else
419 return mid; // key found
420 }
421 return -(low + 1); // key not found
422 }
423
424 /**
425 * Reverses the order of the elements in the specified list.<p>
426 *
427 * This method runs in linear time.
428 *
429 * @param list the list whose elements are to be reversed.
430 * @throws UnsupportedOperationException if the specified list or
431 * its list-iterator does not support the <tt>set</tt> operation.
432 */
433 @SuppressWarnings({"rawtypes", "unchecked"})
434 public static void reverse(List<?> list) {
435 int size = list.size();
436 if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
437 for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
438 swap(list, i, j);
439 } else {
440 // instead of using a raw type here, it's possible to capture
441 // the wildcard but it will require a call to a supplementary
442 // private method
443 ListIterator fwd = list.listIterator();
444 ListIterator rev = list.listIterator(size);
445 for (int i=0, mid=list.size()>>1; i<mid; i++) {
446 Object tmp = fwd.next();
447 fwd.set(rev.previous());
448 rev.set(tmp);
449 }
450 }
451 }
452
453 /**
454 * Randomly permutes the specified list using a default source of
455 * randomness. All permutations occur with approximately equal
456 * likelihood.
457 *
458 * <p>The hedge "approximately" is used in the foregoing description because
459 * default source of randomness is only approximately an unbiased source
460 * of independently chosen bits. If it were a perfect source of randomly
461 * chosen bits, then the algorithm would choose permutations with perfect
462 * uniformity.
463 *
464 * <p>This implementation traverses the list backwards, from the last
465 * element up to the second, repeatedly swapping a randomly selected element
466 * into the "current position". Elements are randomly selected from the
467 * portion of the list that runs from the first element to the current
468 * position, inclusive.
469 *
470 * <p>This method runs in linear time. If the specified list does not
471 * implement the {@link RandomAccess} interface and is large, this
472 * implementation dumps the specified list into an array before shuffling
473 * it, and dumps the shuffled array back into the list. This avoids the
474 * quadratic behavior that would result from shuffling a "sequential
475 * access" list in place.
476 *
477 * @param list the list to be shuffled.
478 * @throws UnsupportedOperationException if the specified list or
479 * its list-iterator does not support the <tt>set</tt> operation.
480 */
481 public static void shuffle(List<?> list) {
482 Random rnd = r;
483 if (rnd == null)
484 r = rnd = new Random(); // harmless race.
485 shuffle(list, rnd);
486 }
487
488 private static Random r;
489
490 /**
491 * Randomly permute the specified list using the specified source of
492 * randomness. All permutations occur with equal likelihood
493 * assuming that the source of randomness is fair.<p>
494 *
495 * This implementation traverses the list backwards, from the last element
496 * up to the second, repeatedly swapping a randomly selected element into
497 * the "current position". Elements are randomly selected from the
498 * portion of the list that runs from the first element to the current
499 * position, inclusive.<p>
500 *
501 * This method runs in linear time. If the specified list does not
502 * implement the {@link RandomAccess} interface and is large, this
503 * implementation dumps the specified list into an array before shuffling
504 * it, and dumps the shuffled array back into the list. This avoids the
505 * quadratic behavior that would result from shuffling a "sequential
506 * access" list in place.
507 *
508 * @param list the list to be shuffled.
509 * @param rnd the source of randomness to use to shuffle the list.
510 * @throws UnsupportedOperationException if the specified list or its
511 * list-iterator does not support the <tt>set</tt> operation.
512 */
513 @SuppressWarnings({"rawtypes", "unchecked"})
514 public static void shuffle(List<?> list, Random rnd) {
515 int size = list.size();
516 if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
517 for (int i=size; i>1; i--)
518 swap(list, i-1, rnd.nextInt(i));
519 } else {
520 Object arr[] = list.toArray();
521
522 // Shuffle array
523 for (int i=size; i>1; i--)
524 swap(arr, i-1, rnd.nextInt(i));
525
526 // Dump array back into list
527 // instead of using a raw type here, it's possible to capture
528 // the wildcard but it will require a call to a supplementary
529 // private method
530 ListIterator it = list.listIterator();
531 for (int i=0; i<arr.length; i++) {
532 it.next();
533 it.set(arr[i]);
534 }
535 }
536 }
537
538 /**
539 * Swaps the elements at the specified positions in the specified list.
540 * (If the specified positions are equal, invoking this method leaves
541 * the list unchanged.)
542 *
543 * @param list The list in which to swap elements.
544 * @param i the index of one element to be swapped.
545 * @param j the index of the other element to be swapped.
546 * @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt>
547 * is out of range (i < 0 || i >= list.size()
548 * || j < 0 || j >= list.size()).
549 * @since 1.4
550 */
551 @SuppressWarnings({"rawtypes", "unchecked"})
552 public static void swap(List<?> list, int i, int j) {
553 // instead of using a raw type here, it's possible to capture
554 // the wildcard but it will require a call to a supplementary
555 // private method
556 final List l = list;
557 l.set(i, l.set(j, l.get(i)));
558 }
559
560 /**
561 * Swaps the two specified elements in the specified array.
562 */
563 private static void swap(Object[] arr, int i, int j) {
564 Object tmp = arr[i];
565 arr[i] = arr[j];
566 arr[j] = tmp;
567 }
568
569 /**
570 * Replaces all of the elements of the specified list with the specified
571 * element. <p>
572 *
573 * This method runs in linear time.
574 *
575 * @param <T> the class of the objects in the list
576 * @param list the list to be filled with the specified element.
577 * @param obj The element with which to fill the specified list.
578 * @throws UnsupportedOperationException if the specified list or its
579 * list-iterator does not support the <tt>set</tt> operation.
580 */
581 public static <T> void fill(List<? super T> list, T obj) {
582 int size = list.size();
583
584 if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
585 for (int i=0; i<size; i++)
586 list.set(i, obj);
587 } else {
588 ListIterator<? super T> itr = list.listIterator();
589 for (int i=0; i<size; i++) {
590 itr.next();
591 itr.set(obj);
592 }
593 }
594 }
595
596 /**
597 * Copies all of the elements from one list into another. After the
598 * operation, the index of each copied element in the destination list
599 * will be identical to its index in the source list. The destination
600 * list must be at least as long as the source list. If it is longer, the
601 * remaining elements in the destination list are unaffected. <p>
602 *
603 * This method runs in linear time.
604 *
605 * @param <T> the class of the objects in the lists
606 * @param dest The destination list.
607 * @param src The source list.
608 * @throws IndexOutOfBoundsException if the destination list is too small
609 * to contain the entire source List.
610 * @throws UnsupportedOperationException if the destination list's
611 * list-iterator does not support the <tt>set</tt> operation.
612 */
613 public static <T> void copy(List<? super T> dest, List<? extends T> src) {
614 int srcSize = src.size();
615 if (srcSize > dest.size())
616 throw new IndexOutOfBoundsException("Source does not fit in dest");
617
618 if (srcSize < COPY_THRESHOLD ||
619 (src instanceof RandomAccess && dest instanceof RandomAccess)) {
620 for (int i=0; i<srcSize; i++)
621 dest.set(i, src.get(i));
622 } else {
623 ListIterator<? super T> di=dest.listIterator();
624 ListIterator<? extends T> si=src.listIterator();
625 for (int i=0; i<srcSize; i++) {
626 di.next();
627 di.set(si.next());
628 }
629 }
630 }
631
632 /**
633 * Returns the minimum element of the given collection, according to the
634 * <i>natural ordering</i> of its elements. All elements in the
635 * collection must implement the <tt>Comparable</tt> interface.
636 * Furthermore, all elements in the collection must be <i>mutually
637 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
638 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
639 * <tt>e2</tt> in the collection).<p>
640 *
641 * This method iterates over the entire collection, hence it requires
642 * time proportional to the size of the collection.
643 *
644 * @param <T> the class of the objects in the collection
645 * @param coll the collection whose minimum element is to be determined.
646 * @return the minimum element of the given collection, according
647 * to the <i>natural ordering</i> of its elements.
648 * @throws ClassCastException if the collection contains elements that are
649 * not <i>mutually comparable</i> (for example, strings and
650 * integers).
651 * @throws NoSuchElementException if the collection is empty.
652 * @see Comparable
653 */
654 public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
655 Iterator<? extends T> i = coll.iterator();
656 T candidate = i.next();
657
658 while (i.hasNext()) {
659 T next = i.next();
660 if (next.compareTo(candidate) < 0)
661 candidate = next;
662 }
663 return candidate;
664 }
665
666 /**
667 * Returns the minimum element of the given collection, according to the
668 * order induced by the specified comparator. All elements in the
669 * collection must be <i>mutually comparable</i> by the specified
670 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
671 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
672 * <tt>e2</tt> in the collection).<p>
673 *
674 * This method iterates over the entire collection, hence it requires
675 * time proportional to the size of the collection.
676 *
677 * @param <T> the class of the objects in the collection
678 * @param coll the collection whose minimum element is to be determined.
679 * @param comp the comparator with which to determine the minimum element.
680 * A <tt>null</tt> value indicates that the elements' <i>natural
681 * ordering</i> should be used.
682 * @return the minimum element of the given collection, according
683 * to the specified comparator.
684 * @throws ClassCastException if the collection contains elements that are
685 * not <i>mutually comparable</i> using the specified comparator.
686 * @throws NoSuchElementException if the collection is empty.
687 * @see Comparable
688 */
689 @SuppressWarnings({"unchecked", "rawtypes"})
690 public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
691 if (comp==null)
692 return (T)min((Collection) coll);
693
694 Iterator<? extends T> i = coll.iterator();
695 T candidate = i.next();
696
697 while (i.hasNext()) {
698 T next = i.next();
699 if (comp.compare(next, candidate) < 0)
700 candidate = next;
701 }
702 return candidate;
703 }
704
705 /**
706 * Returns the maximum element of the given collection, according to the
707 * <i>natural ordering</i> of its elements. All elements in the
708 * collection must implement the <tt>Comparable</tt> interface.
709 * Furthermore, all elements in the collection must be <i>mutually
710 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
711 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
712 * <tt>e2</tt> in the collection).<p>
713 *
714 * This method iterates over the entire collection, hence it requires
715 * time proportional to the size of the collection.
716 *
717 * @param <T> the class of the objects in the collection
718 * @param coll the collection whose maximum element is to be determined.
719 * @return the maximum element of the given collection, according
720 * to the <i>natural ordering</i> of its elements.
721 * @throws ClassCastException if the collection contains elements that are
722 * not <i>mutually comparable</i> (for example, strings and
723 * integers).
724 * @throws NoSuchElementException if the collection is empty.
725 * @see Comparable
726 */
727 public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
728 Iterator<? extends T> i = coll.iterator();
729 T candidate = i.next();
730
731 while (i.hasNext()) {
732 T next = i.next();
733 if (next.compareTo(candidate) > 0)
734 candidate = next;
735 }
736 return candidate;
737 }
738
739 /**
740 * Returns the maximum element of the given collection, according to the
741 * order induced by the specified comparator. All elements in the
742 * collection must be <i>mutually comparable</i> by the specified
743 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
744 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
745 * <tt>e2</tt> in the collection).<p>
746 *
747 * This method iterates over the entire collection, hence it requires
748 * time proportional to the size of the collection.
749 *
750 * @param <T> the class of the objects in the collection
751 * @param coll the collection whose maximum element is to be determined.
752 * @param comp the comparator with which to determine the maximum element.
753 * A <tt>null</tt> value indicates that the elements' <i>natural
754 * ordering</i> should be used.
755 * @return the maximum element of the given collection, according
756 * to the specified comparator.
757 * @throws ClassCastException if the collection contains elements that are
758 * not <i>mutually comparable</i> using the specified comparator.
759 * @throws NoSuchElementException if the collection is empty.
760 * @see Comparable
761 */
762 @SuppressWarnings({"unchecked", "rawtypes"})
763 public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
764 if (comp==null)
765 return (T)max((Collection) coll);
766
767 Iterator<? extends T> i = coll.iterator();
768 T candidate = i.next();
769
770 while (i.hasNext()) {
771 T next = i.next();
772 if (comp.compare(next, candidate) > 0)
773 candidate = next;
774 }
775 return candidate;
776 }
777
778 /**
779 * Rotates the elements in the specified list by the specified distance.
780 * After calling this method, the element at index <tt>i</tt> will be
781 * the element previously at index <tt>(i - distance)</tt> mod
782 * <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt>
783 * and <tt>list.size()-1</tt>, inclusive. (This method has no effect on
784 * the size of the list.)
785 *
786 * <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>.
787 * After invoking <tt>Collections.rotate(list, 1)</tt> (or
788 * <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise
789 * <tt>[s, t, a, n, k]</tt>.
790 *
791 * <p>Note that this method can usefully be applied to sublists to
792 * move one or more elements within a list while preserving the
793 * order of the remaining elements. For example, the following idiom
794 * moves the element at index <tt>j</tt> forward to position
795 * <tt>k</tt> (which must be greater than or equal to <tt>j</tt>):
796 * <pre>
797 * Collections.rotate(list.subList(j, k+1), -1);
798 * </pre>
799 * To make this concrete, suppose <tt>list</tt> comprises
800 * <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt>
801 * (<tt>b</tt>) forward two positions, perform the following invocation:
802 * <pre>
803 * Collections.rotate(l.subList(1, 4), -1);
804 * </pre>
805 * The resulting list is <tt>[a, c, d, b, e]</tt>.
806 *
807 * <p>To move more than one element forward, increase the absolute value
808 * of the rotation distance. To move elements backward, use a positive
809 * shift distance.
810 *
811 * <p>If the specified list is small or implements the {@link
812 * RandomAccess} interface, this implementation exchanges the first
813 * element into the location it should go, and then repeatedly exchanges
814 * the displaced element into the location it should go until a displaced
815 * element is swapped into the first element. If necessary, the process
816 * is repeated on the second and successive elements, until the rotation
817 * is complete. If the specified list is large and doesn't implement the
818 * <tt>RandomAccess</tt> interface, this implementation breaks the
819 * list into two sublist views around index <tt>-distance mod size</tt>.
820 * Then the {@link #reverse(List)} method is invoked on each sublist view,
821 * and finally it is invoked on the entire list. For a more complete
822 * description of both algorithms, see Section 2.3 of Jon Bentley's
823 * <i>Programming Pearls</i> (Addison-Wesley, 1986).
824 *
825 * @param list the list to be rotated.
826 * @param distance the distance to rotate the list. There are no
827 * constraints on this value; it may be zero, negative, or
828 * greater than <tt>list.size()</tt>.
829 * @throws UnsupportedOperationException if the specified list or
830 * its list-iterator does not support the <tt>set</tt> operation.
831 * @since 1.4
832 */
833 public static void rotate(List<?> list, int distance) {
834 if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
835 rotate1(list, distance);
836 else
837 rotate2(list, distance);
838 }
839
840 private static <T> void rotate1(List<T> list, int distance) {
841 int size = list.size();
842 if (size == 0)
843 return;
844 distance = distance % size;
845 if (distance < 0)
846 distance += size;
847 if (distance == 0)
848 return;
849
850 for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
851 T displaced = list.get(cycleStart);
852 int i = cycleStart;
853 do {
854 i += distance;
855 if (i >= size)
856 i -= size;
857 displaced = list.set(i, displaced);
858 nMoved ++;
859 } while (i != cycleStart);
860 }
861 }
862
863 private static void rotate2(List<?> list, int distance) {
864 int size = list.size();
865 if (size == 0)
866 return;
867 int mid = -distance % size;
868 if (mid < 0)
869 mid += size;
870 if (mid == 0)
871 return;
872
873 reverse(list.subList(0, mid));
874 reverse(list.subList(mid, size));
875 reverse(list);
876 }
877
878 /**
879 * Replaces all occurrences of one specified value in a list with another.
880 * More formally, replaces with <tt>newVal</tt> each element <tt>e</tt>
881 * in <tt>list</tt> such that
882 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
883 * (This method has no effect on the size of the list.)
884 *
885 * @param <T> the class of the objects in the list
886 * @param list the list in which replacement is to occur.
887 * @param oldVal the old value to be replaced.
888 * @param newVal the new value with which <tt>oldVal</tt> is to be
889 * replaced.
890 * @return <tt>true</tt> if <tt>list</tt> contained one or more elements
891 * <tt>e</tt> such that
892 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
893 * @throws UnsupportedOperationException if the specified list or
894 * its list-iterator does not support the <tt>set</tt> operation.
895 * @since 1.4
896 */
897 public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
898 boolean result = false;
899 int size = list.size();
900 if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
901 if (oldVal==null) {
902 for (int i=0; i<size; i++) {
903 if (list.get(i)==null) {
904 list.set(i, newVal);
905 result = true;
906 }
907 }
908 } else {
909 for (int i=0; i<size; i++) {
910 if (oldVal.equals(list.get(i))) {
911 list.set(i, newVal);
912 result = true;
913 }
914 }
915 }
916 } else {
917 ListIterator<T> itr=list.listIterator();
918 if (oldVal==null) {
919 for (int i=0; i<size; i++) {
920 if (itr.next()==null) {
921 itr.set(newVal);
922 result = true;
923 }
924 }
925 } else {
926 for (int i=0; i<size; i++) {
927 if (oldVal.equals(itr.next())) {
928 itr.set(newVal);
929 result = true;
930 }
931 }
932 }
933 }
934 return result;
935 }
936
937 /**
938 * Returns the starting position of the first occurrence of the specified
939 * target list within the specified source list, or -1 if there is no
940 * such occurrence. More formally, returns the lowest index <tt>i</tt>
941 * such that {@code source.subList(i, i+target.size()).equals(target)},
942 * or -1 if there is no such index. (Returns -1 if
943 * {@code target.size() > source.size()})
944 *
945 * <p>This implementation uses the "brute force" technique of scanning
946 * over the source list, looking for a match with the target at each
947 * location in turn.
948 *
949 * @param source the list in which to search for the first occurrence
950 * of <tt>target</tt>.
951 * @param target the list to search for as a subList of <tt>source</tt>.
952 * @return the starting position of the first occurrence of the specified
953 * target list within the specified source list, or -1 if there
954 * is no such occurrence.
955 * @since 1.4
956 */
957 public static int indexOfSubList(List<?> source, List<?> target) {
958 int sourceSize = source.size();
959 int targetSize = target.size();
960 int maxCandidate = sourceSize - targetSize;
961
962 if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
963 (source instanceof RandomAccess&&target instanceof RandomAccess)) {
964 nextCand:
965 for (int candidate = 0; candidate <= maxCandidate; candidate++) {
966 for (int i=0, j=candidate; i<targetSize; i++, j++)
967 if (!eq(target.get(i), source.get(j)))
968 continue nextCand; // Element mismatch, try next cand
969 return candidate; // All elements of candidate matched target
970 }
971 } else { // Iterator version of above algorithm
972 ListIterator<?> si = source.listIterator();
973 nextCand:
974 for (int candidate = 0; candidate <= maxCandidate; candidate++) {
975 ListIterator<?> ti = target.listIterator();
976 for (int i=0; i<targetSize; i++) {
977 if (!eq(ti.next(), si.next())) {
978 // Back up source iterator to next candidate
979 for (int j=0; j<i; j++)
980 si.previous();
981 continue nextCand;
982 }
983 }
984 return candidate;
985 }
986 }
987 return -1; // No candidate matched the target
988 }
989
990 /**
991 * Returns the starting position of the last occurrence of the specified
992 * target list within the specified source list, or -1 if there is no such
993 * occurrence. More formally, returns the highest index <tt>i</tt>
994 * such that {@code source.subList(i, i+target.size()).equals(target)},
995 * or -1 if there is no such index. (Returns -1 if
996 * {@code target.size() > source.size()})
997 *
998 * <p>This implementation uses the "brute force" technique of iterating
999 * over the source list, looking for a match with the target at each
1000 * location in turn.
1001 *
1002 * @param source the list in which to search for the last occurrence
1003 * of <tt>target</tt>.
1004 * @param target the list to search for as a subList of <tt>source</tt>.
1005 * @return the starting position of the last occurrence of the specified
1006 * target list within the specified source list, or -1 if there
1007 * is no such occurrence.
1008 * @since 1.4
1009 */
1010 public static int lastIndexOfSubList(List<?> source, List<?> target) {
1011 int sourceSize = source.size();
1012 int targetSize = target.size();
1013 int maxCandidate = sourceSize - targetSize;
1014
1015 if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
1016 source instanceof RandomAccess) { // Index access version
1017 nextCand:
1018 for (int candidate = maxCandidate; candidate >= 0; candidate--) {
1019 for (int i=0, j=candidate; i<targetSize; i++, j++)
1020 if (!eq(target.get(i), source.get(j)))
1021 continue nextCand; // Element mismatch, try next cand
1022 return candidate; // All elements of candidate matched target
1023 }
1024 } else { // Iterator version of above algorithm
1025 if (maxCandidate < 0)
1026 return -1;
1027 ListIterator<?> si = source.listIterator(maxCandidate);
1028 nextCand:
1029 for (int candidate = maxCandidate; candidate >= 0; candidate--) {
1030 ListIterator<?> ti = target.listIterator();
1031 for (int i=0; i<targetSize; i++) {
1032 if (!eq(ti.next(), si.next())) {
1033 if (candidate != 0) {
1034 // Back up source iterator to next candidate
1035 for (int j=0; j<=i+1; j++)
1036 si.previous();
1037 }
1038 continue nextCand;
1039 }
1040 }
1041 return candidate;
1042 }
1043 }
1044 return -1; // No candidate matched the target
1045 }
1046
1047
1048 // Unmodifiable Wrappers
1049
1050 /**
1051 * Returns an unmodifiable view of the specified collection. This method
1052 * allows modules to provide users with "read-only" access to internal
1053 * collections. Query operations on the returned collection "read through"
1054 * to the specified collection, and attempts to modify the returned
1055 * collection, whether direct or via its iterator, result in an
1056 * <tt>UnsupportedOperationException</tt>.<p>
1057 *
1058 * The returned collection does <i>not</i> pass the hashCode and equals
1059 * operations through to the backing collection, but relies on
1060 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
1061 * is necessary to preserve the contracts of these operations in the case
1062 * that the backing collection is a set or a list.<p>
1063 *
1064 * The returned collection will be serializable if the specified collection
1065 * is serializable.
1066 *
1067 * @param <T> the class of the objects in the collection
1068 * @param c the collection for which an unmodifiable view is to be
1069 * returned.
1070 * @return an unmodifiable view of the specified collection.
1071 */
1072 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
1073 return new UnmodifiableCollection<>(c);
1074 }
1075
1076 /**
1077 * @serial include
1078 */
1079 static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
1080 private static final long serialVersionUID = 1820017752578914078L;
1081
1082 final Collection<? extends E> c;
1083
1084 UnmodifiableCollection(Collection<? extends E> c) {
1085 if (c==null)
1086 throw new NullPointerException();
1087 this.c = c;
1088 }
1089
1090 public int size() {return c.size();}
1091 public boolean isEmpty() {return c.isEmpty();}
1092 public boolean contains(Object o) {return c.contains(o);}
1093 public Object[] toArray() {return c.toArray();}
1094 public <T> T[] toArray(T[] a) {return c.toArray(a);}
1095 public String toString() {return c.toString();}
1096
1097 public Iterator<E> iterator() {
1098 return new Iterator<E>() {
1099 private final Iterator<? extends E> i = c.iterator();
1100
1101 public boolean hasNext() {return i.hasNext();}
1102 public E next() {return i.next();}
1103 public void remove() {
1104 throw new UnsupportedOperationException();
1105 }
1106 @Override
1107 public void forEachRemaining(Consumer<? super E> action) {
1108 // Use backing collection version
1109 i.forEachRemaining(action);
1110 }
1111 };
1112 }
1113
1114 public boolean add(E e) {
1115 throw new UnsupportedOperationException();
1116 }
1117 public boolean remove(Object o) {
1118 throw new UnsupportedOperationException();
1119 }
1120
1121 public boolean containsAll(Collection<?> coll) {
1122 return c.containsAll(coll);
1123 }
1124 public boolean addAll(Collection<? extends E> coll) {
1125 throw new UnsupportedOperationException();
1126 }
1127 public boolean removeAll(Collection<?> coll) {
1128 throw new UnsupportedOperationException();
1129 }
1130 public boolean retainAll(Collection<?> coll) {
1131 throw new UnsupportedOperationException();
1132 }
1133 public void clear() {
1134 throw new UnsupportedOperationException();
1135 }
1136
1137 // Override default methods in Collection
1138 @Override
1139 public void forEach(Consumer<? super E> action) {
1140 c.forEach(action);
1141 }
1142 @Override
1143 public boolean removeIf(Predicate<? super E> filter) {
1144 throw new UnsupportedOperationException();
1145 }
1146 @Override
1147 public Spliterator<E> spliterator() {
1148 return (Spliterator<E>)c.spliterator();
1149 }
1150
1151 }
1152
1153 /**
1154 * Returns an unmodifiable view of the specified set. This method allows
1155 * modules to provide users with "read-only" access to internal sets.
1156 * Query operations on the returned set "read through" to the specified
1157 * set, and attempts to modify the returned set, whether direct or via its
1158 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
1159 *
1160 * The returned set will be serializable if the specified set
1161 * is serializable.
1162 *
1163 * @param <T> the class of the objects in the set
1164 * @param s the set for which an unmodifiable view is to be returned.
1165 * @return an unmodifiable view of the specified set.
1166 */
1167 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
1168 return new UnmodifiableSet<>(s);
1169 }
1170
1171 /**
1172 * @serial include
1173 */
1174 static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
1175 implements Set<E>, Serializable {
1176 private static final long serialVersionUID = -9215047833775013803L;
1177
1178 UnmodifiableSet(Set<? extends E> s) {super(s);}
1179 public boolean equals(Object o) {return o == this || c.equals(o);}
1180 public int hashCode() {return c.hashCode();}
1181 }
1182
1183 /**
1184 * Returns an unmodifiable view of the specified sorted set. This method
1185 * allows modules to provide users with "read-only" access to internal
1186 * sorted sets. Query operations on the returned sorted set "read
1187 * through" to the specified sorted set. Attempts to modify the returned
1188 * sorted set, whether direct, via its iterator, or via its
1189 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
1190 * an <tt>UnsupportedOperationException</tt>.<p>
1191 *
1192 * The returned sorted set will be serializable if the specified sorted set
1193 * is serializable.
1194 *
1195 * @param <T> the class of the objects in the set
1196 * @param s the sorted set for which an unmodifiable view is to be
1197 * returned.
1198 * @return an unmodifiable view of the specified sorted set.
1199 */
1200 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
1201 return new UnmodifiableSortedSet<>(s);
1202 }
1203
1204 /**
1205 * @serial include
1206 */
1207 static class UnmodifiableSortedSet<E>
1208 extends UnmodifiableSet<E>
1209 implements SortedSet<E>, Serializable {
1210 private static final long serialVersionUID = -4929149591599911165L;
1211 private final SortedSet<E> ss;
1212
1213 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
1214
1215 public Comparator<? super E> comparator() {return ss.comparator();}
1216
1217 public SortedSet<E> subSet(E fromElement, E toElement) {
1218 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
1219 }
1220 public SortedSet<E> headSet(E toElement) {
1221 return new UnmodifiableSortedSet<>(ss.headSet(toElement));
1222 }
1223 public SortedSet<E> tailSet(E fromElement) {
1224 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
1225 }
1226
1227 public E first() {return ss.first();}
1228 public E last() {return ss.last();}
1229 }
1230
1231 /**
1232 * Returns an unmodifiable view of the specified navigable set. This method
1233 * allows modules to provide users with "read-only" access to internal
1234 * navigable sets. Query operations on the returned navigable set "read
1235 * through" to the specified navigable set. Attempts to modify the returned
1236 * navigable set, whether direct, via its iterator, or via its
1237 * {@code subSet}, {@code headSet}, or {@code tailSet} views, result in
1238 * an {@code UnsupportedOperationException}.<p>
1239 *
1240 * The returned navigable set will be serializable if the specified
1241 * navigable set is serializable.
1242 *
1243 * @param <T> the class of the objects in the set
1244 * @param s the navigable set for which an unmodifiable view is to be
1245 * returned
1246 * @return an unmodifiable view of the specified navigable set
1247 * @since 1.8
1248 */
1249 public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
1250 return new UnmodifiableNavigableSet<>(s);
1251 }
1252
1253 /**
1254 * Wraps a navigable set and disables all of the mutative operations.
1255 *
1256 * @param <E> type of elements
1257 * @serial include
1258 */
1259 static class UnmodifiableNavigableSet<E>
1260 extends UnmodifiableSortedSet<E>
1261 implements NavigableSet<E>, Serializable {
1262
1263 private static final long serialVersionUID = -6027448201786391929L;
1264
1265 /**
1266 * A singleton empty unmodifiable navigable set used for
1267 * {@link #emptyNavigableSet()}.
1268 *
1269 * @param <E> type of elements, if there were any, and bounds
1270 */
1271 private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E>
1272 implements Serializable {
1273 private static final long serialVersionUID = -6291252904449939134L;
1274
1275 public EmptyNavigableSet() {
1276 super(new TreeSet<E>());
1277 }
1278
1279 private Object readResolve() { return EMPTY_NAVIGABLE_SET; }
1280 }
1281
1282 @SuppressWarnings("rawtypes")
1283 private static final NavigableSet<?> EMPTY_NAVIGABLE_SET =
1284 new EmptyNavigableSet<>();
1285
1286 /**
1287 * The instance we are protecting.
1288 */
1289 private final NavigableSet<E> ns;
1290
1291 UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;}
1292
1293 public E lower(E e) { return ns.lower(e); }
1294 public E floor(E e) { return ns.floor(e); }
1295 public E ceiling(E e) { return ns.ceiling(e); }
1296 public E higher(E e) { return ns.higher(e); }
1297 public E pollFirst() { throw new UnsupportedOperationException(); }
1298 public E pollLast() { throw new UnsupportedOperationException(); }
1299 public NavigableSet<E> descendingSet()
1300 { return new UnmodifiableNavigableSet<>(ns.descendingSet()); }
1301 public Iterator<E> descendingIterator()
1302 { return descendingSet().iterator(); }
1303
1304 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
1305 return new UnmodifiableNavigableSet<>(
1306 ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
1307 }
1308
1309 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
1310 return new UnmodifiableNavigableSet<>(
1311 ns.headSet(toElement, inclusive));
1312 }
1313
1314 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
1315 return new UnmodifiableNavigableSet<>(
1316 ns.tailSet(fromElement, inclusive));
1317 }
1318 }
1319
1320 /**
1321 * Returns an unmodifiable view of the specified list. This method allows
1322 * modules to provide users with "read-only" access to internal
1323 * lists. Query operations on the returned list "read through" to the
1324 * specified list, and attempts to modify the returned list, whether
1325 * direct or via its iterator, result in an
1326 * <tt>UnsupportedOperationException</tt>.<p>
1327 *
1328 * The returned list will be serializable if the specified list
1329 * is serializable. Similarly, the returned list will implement
1330 * {@link RandomAccess} if the specified list does.
1331 *
1332 * @param <T> the class of the objects in the list
1333 * @param list the list for which an unmodifiable view is to be returned.
1334 * @return an unmodifiable view of the specified list.
1335 */
1336 public static <T> List<T> unmodifiableList(List<? extends T> list) {
1337 return (list instanceof RandomAccess ?
1338 new UnmodifiableRandomAccessList<>(list) :
1339 new UnmodifiableList<>(list));
1340 }
1341
1342 /**
1343 * @serial include
1344 */
1345 static class UnmodifiableList<E> extends UnmodifiableCollection<E>
1346 implements List<E> {
1347 private static final long serialVersionUID = -283967356065247728L;
1348
1349 final List<? extends E> list;
1350
1351 UnmodifiableList(List<? extends E> list) {
1352 super(list);
1353 this.list = list;
1354 }
1355
1356 public boolean equals(Object o) {return o == this || list.equals(o);}
1357 public int hashCode() {return list.hashCode();}
1358
1359 public E get(int index) {return list.get(index);}
1360 public E set(int index, E element) {
1361 throw new UnsupportedOperationException();
1362 }
1363 public void add(int index, E element) {
1364 throw new UnsupportedOperationException();
1365 }
1366 public E remove(int index) {
1367 throw new UnsupportedOperationException();
1368 }
1369 public int indexOf(Object o) {return list.indexOf(o);}
1370 public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
1371 public boolean addAll(int index, Collection<? extends E> c) {
1372 throw new UnsupportedOperationException();
1373 }
1374
1375 @Override
1376 public void replaceAll(UnaryOperator<E> operator) {
1377 throw new UnsupportedOperationException();
1378 }
1379 @Override
1380 public void sort(Comparator<? super E> c) {
1381 throw new UnsupportedOperationException();
1382 }
1383
1384 public ListIterator<E> listIterator() {return listIterator(0);}
1385
1386 public ListIterator<E> listIterator(final int index) {
1387 return new ListIterator<E>() {
1388 private final ListIterator<? extends E> i
1389 = list.listIterator(index);
1390
1391 public boolean hasNext() {return i.hasNext();}
1392 public E next() {return i.next();}
1393 public boolean hasPrevious() {return i.hasPrevious();}
1394 public E previous() {return i.previous();}
1395 public int nextIndex() {return i.nextIndex();}
1396 public int previousIndex() {return i.previousIndex();}
1397
1398 public void remove() {
1399 throw new UnsupportedOperationException();
1400 }
1401 public void set(E e) {
1402 throw new UnsupportedOperationException();
1403 }
1404 public void add(E e) {
1405 throw new UnsupportedOperationException();
1406 }
1407
1408 @Override
1409 public void forEachRemaining(Consumer<? super E> action) {
1410 i.forEachRemaining(action);
1411 }
1412 };
1413 }
1414
1415 public List<E> subList(int fromIndex, int toIndex) {
1416 return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
1417 }
1418
1419 /**
1420 * UnmodifiableRandomAccessList instances are serialized as
1421 * UnmodifiableList instances to allow them to be deserialized
1422 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
1423 * This method inverts the transformation. As a beneficial
1424 * side-effect, it also grafts the RandomAccess marker onto
1425 * UnmodifiableList instances that were serialized in pre-1.4 JREs.
1426 *
1427 * Note: Unfortunately, UnmodifiableRandomAccessList instances
1428 * serialized in 1.4.1 and deserialized in 1.4 will become
1429 * UnmodifiableList instances, as this method was missing in 1.4.
1430 */
1431 private Object readResolve() {
1432 return (list instanceof RandomAccess
1433 ? new UnmodifiableRandomAccessList<>(list)
1434 : this);
1435 }
1436 }
1437
1438 /**
1439 * @serial include
1440 */
1441 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
1442 implements RandomAccess
1443 {
1444 UnmodifiableRandomAccessList(List<? extends E> list) {
1445 super(list);
1446 }
1447
1448 public List<E> subList(int fromIndex, int toIndex) {
1449 return new UnmodifiableRandomAccessList<>(
1450 list.subList(fromIndex, toIndex));
1451 }
1452
1453 private static final long serialVersionUID = -2542308836966382001L;
1454
1455 /**
1456 * Allows instances to be deserialized in pre-1.4 JREs (which do
1457 * not have UnmodifiableRandomAccessList). UnmodifiableList has
1458 * a readResolve method that inverts this transformation upon
1459 * deserialization.
1460 */
1461 private Object writeReplace() {
1462 return new UnmodifiableList<>(list);
1463 }
1464 }
1465
1466 /**
1467 * Returns an unmodifiable view of the specified map. This method
1468 * allows modules to provide users with "read-only" access to internal
1469 * maps. Query operations on the returned map "read through"
1470 * to the specified map, and attempts to modify the returned
1471 * map, whether direct or via its collection views, result in an
1472 * <tt>UnsupportedOperationException</tt>.<p>
1473 *
1474 * The returned map will be serializable if the specified map
1475 * is serializable.
1476 *
1477 * @param <K> the class of the map keys
1478 * @param <V> the class of the map values
1479 * @param m the map for which an unmodifiable view is to be returned.
1480 * @return an unmodifiable view of the specified map.
1481 */
1482 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
1483 return new UnmodifiableMap<>(m);
1484 }
1485
1486 /**
1487 * @serial include
1488 */
1489 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
1490 private static final long serialVersionUID = -1034234728574286014L;
1491
1492 private final Map<? extends K, ? extends V> m;
1493
1494 UnmodifiableMap(Map<? extends K, ? extends V> m) {
1495 if (m==null)
1496 throw new NullPointerException();
1497 this.m = m;
1498 }
1499
1500 public int size() {return m.size();}
1501 public boolean isEmpty() {return m.isEmpty();}
1502 public boolean containsKey(Object key) {return m.containsKey(key);}
1503 public boolean containsValue(Object val) {return m.containsValue(val);}
1504 public V get(Object key) {return m.get(key);}
1505
1506 public V put(K key, V value) {
1507 throw new UnsupportedOperationException();
1508 }
1509 public V remove(Object key) {
1510 throw new UnsupportedOperationException();
1511 }
1512 public void putAll(Map<? extends K, ? extends V> m) {
1513 throw new UnsupportedOperationException();
1514 }
1515 public void clear() {
1516 throw new UnsupportedOperationException();
1517 }
1518
1519 private transient Set<K> keySet = null;
1520 private transient Set<Map.Entry<K,V>> entrySet = null;
1521 private transient Collection<V> values = null;
1522
1523 public Set<K> keySet() {
1524 if (keySet==null)
1525 keySet = unmodifiableSet(m.keySet());
1526 return keySet;
1527 }
1528
1529 public Set<Map.Entry<K,V>> entrySet() {
1530 if (entrySet==null)
1531 entrySet = new UnmodifiableEntrySet<>(m.entrySet());
1532 return entrySet;
1533 }
1534
1535 public Collection<V> values() {
1536 if (values==null)
1537 values = unmodifiableCollection(m.values());
1538 return values;
1539 }
1540
1541 public boolean equals(Object o) {return o == this || m.equals(o);}
1542 public int hashCode() {return m.hashCode();}
1543 public String toString() {return m.toString();}
1544
1545 // Override default methods in Map
1546 @Override
1547 @SuppressWarnings("unchecked")
1548 public V getOrDefault(Object k, V defaultValue) {
1549 // Safe cast as we don't change the value
1550 return ((Map<K, V>)m).getOrDefault(k, defaultValue);
1551 }
1552
1553 @Override
1554 public void forEach(BiConsumer<? super K, ? super V> action) {
1555 m.forEach(action);
1556 }
1557
1558 @Override
1559 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1560 throw new UnsupportedOperationException();
1561 }
1562
1563 @Override
1564 public V putIfAbsent(K key, V value) {
1565 throw new UnsupportedOperationException();
1566 }
1567
1568 @Override
1569 public boolean remove(Object key, Object value) {
1570 throw new UnsupportedOperationException();
1571 }
1572
1573 @Override
1574 public boolean replace(K key, V oldValue, V newValue) {
1575 throw new UnsupportedOperationException();
1576 }
1577
1578 @Override
1579 public V replace(K key, V value) {
1580 throw new UnsupportedOperationException();
1581 }
1582
1583 @Override
1584 public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
1585 throw new UnsupportedOperationException();
1586 }
1587
1588 @Override
1589 public V computeIfPresent(K key,
1590 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1591 throw new UnsupportedOperationException();
1592 }
1593
1594 @Override
1595 public V compute(K key,
1596 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1597 throw new UnsupportedOperationException();
1598 }
1599
1600 @Override
1601 public V merge(K key, V value,
1602 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1603 throw new UnsupportedOperationException();
1604 }
1605
1606 /**
1607 * We need this class in addition to UnmodifiableSet as
1608 * Map.Entries themselves permit modification of the backing Map
1609 * via their setValue operation. This class is subtle: there are
1610 * many possible attacks that must be thwarted.
1611 *
1612 * @serial include
1613 */
1614 static class UnmodifiableEntrySet<K,V>
1615 extends UnmodifiableSet<Map.Entry<K,V>> {
1616 private static final long serialVersionUID = 7854390611657943733L;
1617
1618 @SuppressWarnings({"unchecked", "rawtypes"})
1619 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
1620 // Need to cast to raw in order to work around a limitation in the type system
1621 super((Set)s);
1622 }
1623
1624 static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) {
1625 return e -> action.accept(new UnmodifiableEntry<>(e));
1626 }
1627
1628 public void forEach(Consumer<? super Entry<K, V>> action) {
1629 Objects.requireNonNull(action);
1630 c.forEach(entryConsumer(action));
1631 }
1632
1633 static final class UnmodifiableEntrySetSpliterator<K, V>
1634 implements Spliterator<Entry<K,V>> {
1635 final Spliterator<Map.Entry<K, V>> s;
1636
1637 UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>> s) {
1638 this.s = s;
1639 }
1640
1641 @Override
1642 public boolean tryAdvance(Consumer<? super Entry<K, V>> action) {
1643 Objects.requireNonNull(action);
1644 return s.tryAdvance(entryConsumer(action));
1645 }
1646
1647 @Override
1648 public void forEachRemaining(Consumer<? super Entry<K, V>> action) {
1649 Objects.requireNonNull(action);
1650 s.forEachRemaining(entryConsumer(action));
1651 }
1652
1653 @Override
1654 public Spliterator<Entry<K, V>> trySplit() {
1655 Spliterator<Entry<K, V>> split = s.trySplit();
1656 return split == null
1657 ? null
1658 : new UnmodifiableEntrySetSpliterator<>(split);
1659 }
1660
1661 @Override
1662 public long estimateSize() {
1663 return s.estimateSize();
1664 }
1665
1666 @Override
1667 public long getExactSizeIfKnown() {
1668 return s.getExactSizeIfKnown();
1669 }
1670
1671 @Override
1672 public int characteristics() {
1673 return s.characteristics();
1674 }
1675
1676 @Override
1677 public boolean hasCharacteristics(int characteristics) {
1678 return s.hasCharacteristics(characteristics);
1679 }
1680
1681 @Override
1682 public Comparator<? super Entry<K, V>> getComparator() {
1683 return s.getComparator();
1684 }
1685 }
1686
1687 @SuppressWarnings("unchecked")
1688 public Spliterator<Entry<K,V>> spliterator() {
1689 return new UnmodifiableEntrySetSpliterator<>(
1690 (Spliterator<Map.Entry<K, V>>) c.spliterator());
1691 }
1692
1693 @Override
1694 public Stream<Entry<K,V>> stream() {
1695 return StreamSupport.stream(spliterator(), false);
1696 }
1697
1698 @Override
1699 public Stream<Entry<K,V>> parallelStream() {
1700 return StreamSupport.stream(spliterator(), true);
1701 }
1702
1703 public Iterator<Map.Entry<K,V>> iterator() {
1704 return new Iterator<Map.Entry<K,V>>() {
1705 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
1706
1707 public boolean hasNext() {
1708 return i.hasNext();
1709 }
1710 public Map.Entry<K,V> next() {
1711 return new UnmodifiableEntry<>(i.next());
1712 }
1713 public void remove() {
1714 throw new UnsupportedOperationException();
1715 }
1716 };
1717 }
1718
1719 @SuppressWarnings("unchecked")
1720 public Object[] toArray() {
1721 Object[] a = c.toArray();
1722 for (int i=0; i<a.length; i++)
1723 a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]);
1724 return a;
1725 }
1726
1727 @SuppressWarnings("unchecked")
1728 public <T> T[] toArray(T[] a) {
1729 // We don't pass a to c.toArray, to avoid window of
1730 // vulnerability wherein an unscrupulous multithreaded client
1731 // could get his hands on raw (unwrapped) Entries from c.
1732 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
1733
1734 for (int i=0; i<arr.length; i++)
1735 arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]);
1736
1737 if (arr.length > a.length)
1738 return (T[])arr;
1739
1740 System.arraycopy(arr, 0, a, 0, arr.length);
1741 if (a.length > arr.length)
1742 a[arr.length] = null;
1743 return a;
1744 }
1745
1746 /**
1747 * This method is overridden to protect the backing set against
1748 * an object with a nefarious equals function that senses
1749 * that the equality-candidate is Map.Entry and calls its
1750 * setValue method.
1751 */
1752 public boolean contains(Object o) {
1753 if (!(o instanceof Map.Entry))
1754 return false;
1755 return c.contains(
1756 new UnmodifiableEntry<>((Map.Entry<?,?>) o));
1757 }
1758
1759 /**
1760 * The next two methods are overridden to protect against
1761 * an unscrupulous List whose contains(Object o) method senses
1762 * when o is a Map.Entry, and calls o.setValue.
1763 */
1764 public boolean containsAll(Collection<?> coll) {
1765 for (Object e : coll) {
1766 if (!contains(e)) // Invokes safe contains() above
1767 return false;
1768 }
1769 return true;
1770 }
1771 public boolean equals(Object o) {
1772 if (o == this)
1773 return true;
1774
1775 if (!(o instanceof Set))
1776 return false;
1777 Set<?> s = (Set<?>) o;
1778 if (s.size() != c.size())
1779 return false;
1780 return containsAll(s); // Invokes safe containsAll() above
1781 }
1782
1783 /**
1784 * This "wrapper class" serves two purposes: it prevents
1785 * the client from modifying the backing Map, by short-circuiting
1786 * the setValue method, and it protects the backing Map against
1787 * an ill-behaved Map.Entry that attempts to modify another
1788 * Map Entry when asked to perform an equality check.
1789 */
1790 private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
1791 private Map.Entry<? extends K, ? extends V> e;
1792
1793 UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e)
1794 {this.e = Objects.requireNonNull(e);}
1795
1796 public K getKey() {return e.getKey();}
1797 public V getValue() {return e.getValue();}
1798 public V setValue(V value) {
1799 throw new UnsupportedOperationException();
1800 }
1801 public int hashCode() {return e.hashCode();}
1802 public boolean equals(Object o) {
1803 if (this == o)
1804 return true;
1805 if (!(o instanceof Map.Entry))
1806 return false;
1807 Map.Entry<?,?> t = (Map.Entry<?,?>)o;
1808 return eq(e.getKey(), t.getKey()) &&
1809 eq(e.getValue(), t.getValue());
1810 }
1811 public String toString() {return e.toString();}
1812 }
1813 }
1814 }
1815
1816 /**
1817 * Returns an unmodifiable view of the specified sorted map. This method
1818 * allows modules to provide users with "read-only" access to internal
1819 * sorted maps. Query operations on the returned sorted map "read through"
1820 * to the specified sorted map. Attempts to modify the returned
1821 * sorted map, whether direct, via its collection views, or via its
1822 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
1823 * an <tt>UnsupportedOperationException</tt>.<p>
1824 *
1825 * The returned sorted map will be serializable if the specified sorted map
1826 * is serializable.
1827 *
1828 * @param <K> the class of the map keys
1829 * @param <V> the class of the map values
1830 * @param m the sorted map for which an unmodifiable view is to be
1831 * returned.
1832 * @return an unmodifiable view of the specified sorted map.
1833 */
1834 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
1835 return new UnmodifiableSortedMap<>(m);
1836 }
1837
1838 /**
1839 * @serial include
1840 */
1841 static class UnmodifiableSortedMap<K,V>
1842 extends UnmodifiableMap<K,V>
1843 implements SortedMap<K,V>, Serializable {
1844 private static final long serialVersionUID = -8806743815996713206L;
1845
1846 private final SortedMap<K, ? extends V> sm;
1847
1848 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; }
1849 public Comparator<? super K> comparator() { return sm.comparator(); }
1850 public SortedMap<K,V> subMap(K fromKey, K toKey)
1851 { return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); }
1852 public SortedMap<K,V> headMap(K toKey)
1853 { return new UnmodifiableSortedMap<>(sm.headMap(toKey)); }
1854 public SortedMap<K,V> tailMap(K fromKey)
1855 { return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); }
1856 public K firstKey() { return sm.firstKey(); }
1857 public K lastKey() { return sm.lastKey(); }
1858 }
1859
1860 /**
1861 * Returns an unmodifiable view of the specified navigable map. This method
1862 * allows modules to provide users with "read-only" access to internal
1863 * navigable maps. Query operations on the returned navigable map "read
1864 * through" to the specified navigable map. Attempts to modify the returned
1865 * navigable map, whether direct, via its collection views, or via its
1866 * {@code subMap}, {@code headMap}, or {@code tailMap} views, result in
1867 * an {@code UnsupportedOperationException}.<p>
1868 *
1869 * The returned navigable map will be serializable if the specified
1870 * navigable map is serializable.
1871 *
1872 * @param <K> the class of the map keys
1873 * @param <V> the class of the map values
1874 * @param m the navigable map for which an unmodifiable view is to be
1875 * returned
1876 * @return an unmodifiable view of the specified navigable map
1877 * @since 1.8
1878 */
1879 public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {
1880 return new UnmodifiableNavigableMap<>(m);
1881 }
1882
1883 /**
1884 * @serial include
1885 */
1886 static class UnmodifiableNavigableMap<K,V>
1887 extends UnmodifiableSortedMap<K,V>
1888 implements NavigableMap<K,V>, Serializable {
1889 private static final long serialVersionUID = -4858195264774772197L;
1890
1891 /**
1892 * A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve
1893 * to preserve singleton property.
1894 *
1895 * @param <K> type of keys, if there were any, and of bounds
1896 * @param <V> type of values, if there were any
1897 */
1898 private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V>
1899 implements Serializable {
1900
1901 private static final long serialVersionUID = -2239321462712562324L;
1902
1903 EmptyNavigableMap() { super(new TreeMap()); }
1904
1905 @Override
1906 public NavigableSet<K> navigableKeySet()
1907 { return emptyNavigableSet(); }
1908
1909 private Object readResolve() { return EMPTY_NAVIGABLE_MAP; }
1910 }
1911
1912 /**
1913 * Singleton for {@link emptyNavigableMap()} which is also immutable.
1914 */
1915 private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP =
1916 new EmptyNavigableMap<>();
1917
1918 /**
1919 * The instance we wrap and protect.
1920 */
1921 private final NavigableMap<K, ? extends V> nm;
1922
1923 UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m)
1924 {super(m); nm = m;}
1925
1926 public K lowerKey(K key) { return nm.lowerKey(key); }
1927 public K floorKey(K key) { return nm.floorKey(key); }
1928 public K ceilingKey(K key) { return nm.ceilingKey(key); }
1929 public K higherKey(K key) { return nm.higherKey(key); }
1930
1931 public Entry<K, V> lowerEntry(K key) {
1932 Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key);
1933 return (null != lower)
1934 ? new UnmodifiableEntrySet.UnmodifiableEntry(lower)
1935 : null;
1936 }
1937
1938 public Entry<K, V> floorEntry(K key) {
1939 Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key);
1940 return (null != floor)
1941 ? new UnmodifiableEntrySet.UnmodifiableEntry(floor)
1942 : null;
1943 }
1944
1945 public Entry<K, V> ceilingEntry(K key) {
1946 Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key);
1947 return (null != ceiling)
1948 ? new UnmodifiableEntrySet.UnmodifiableEntry(ceiling)
1949 : null;
1950 }
1951
1952
1953 public Entry<K, V> higherEntry(K key) {
1954 Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key);
1955 return (null != higher)
1956 ? new UnmodifiableEntrySet.UnmodifiableEntry(higher)
1957 : null;
1958 }
1959
1960 public Entry<K, V> firstEntry() {
1961 Entry<K,V> first = (Entry<K, V>) nm.firstEntry();
1962 return (null != first)
1963 ? new UnmodifiableEntrySet.UnmodifiableEntry(first)
1964 : null;
1965 }
1966
1967 public Entry<K, V> lastEntry() {
1968 Entry<K,V> last = (Entry<K, V>) nm.lastEntry();
1969 return (null != last)
1970 ? new UnmodifiableEntrySet.UnmodifiableEntry(last)
1971 : null;
1972 }
1973
1974 public Entry<K, V> pollFirstEntry()
1975 { throw new UnsupportedOperationException(); }
1976 public Entry<K, V> pollLastEntry()
1977 { throw new UnsupportedOperationException(); }
1978 public NavigableMap<K, V> descendingMap()
1979 { return unmodifiableNavigableMap(nm.descendingMap()); }
1980 public NavigableSet<K> navigableKeySet()
1981 { return unmodifiableNavigableSet(nm.navigableKeySet()); }
1982 public NavigableSet<K> descendingKeySet()
1983 { return unmodifiableNavigableSet(nm.descendingKeySet()); }
1984
1985 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
1986 return unmodifiableNavigableMap(
1987 nm.subMap(fromKey, fromInclusive, toKey, toInclusive));
1988 }
1989
1990 public NavigableMap<K, V> headMap(K toKey, boolean inclusive)
1991 { return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); }
1992 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive)
1993 { return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); }
1994 }
1995
1996 // Synch Wrappers
1997
1998 /**
1999 * Returns a synchronized (thread-safe) collection backed by the specified
2000 * collection. In order to guarantee serial access, it is critical that
2001 * <strong>all</strong> access to the backing collection is accomplished
2002 * through the returned collection.<p>
2003 *
2004 * It is imperative that the user manually synchronize on the returned
2005 * collection when traversing it via {@link Iterator} or
2006 * {@link Spliterator}:
2007 * <pre>
2008 * Collection c = Collections.synchronizedCollection(myCollection);
2009 * ...
2010 * synchronized (c) {
2011 * Iterator i = c.iterator(); // Must be in the synchronized block
2012 * while (i.hasNext())
2013 * foo(i.next());
2014 * }
2015 * </pre>
2016 * Failure to follow this advice may result in non-deterministic behavior.
2017 *
2018 * <p>The returned collection does <i>not</i> pass the {@code hashCode}
2019 * and {@code equals} operations through to the backing collection, but
2020 * relies on {@code Object}'s equals and hashCode methods. This is
2021 * necessary to preserve the contracts of these operations in the case
2022 * that the backing collection is a set or a list.<p>
2023 *
2024 * The returned collection will be serializable if the specified collection
2025 * is serializable.
2026 *
2027 * @param <T> the class of the objects in the collection
2028 * @param c the collection to be "wrapped" in a synchronized collection.
2029 * @return a synchronized view of the specified collection.
2030 */
2031 public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
2032 return new SynchronizedCollection<>(c);
2033 }
2034
2035 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
2036 return new SynchronizedCollection<>(c, mutex);
2037 }
2038
2039 /**
2040 * @serial include
2041 */
2042 static class SynchronizedCollection<E> implements Collection<E>, Serializable {
2043 private static final long serialVersionUID = 3053995032091335093L;
2044
2045 final Collection<E> c; // Backing Collection
2046 final Object mutex; // Object on which to synchronize
2047
2048 SynchronizedCollection(Collection<E> c) {
2049 this.c = Objects.requireNonNull(c);
2050 mutex = this;
2051 }
2052
2053 SynchronizedCollection(Collection<E> c, Object mutex) {
2054 this.c = Objects.requireNonNull(c);
2055 this.mutex = Objects.requireNonNull(mutex);
2056 }
2057
2058 public int size() {
2059 synchronized (mutex) {return c.size();}
2060 }
2061 public boolean isEmpty() {
2062 synchronized (mutex) {return c.isEmpty();}
2063 }
2064 public boolean contains(Object o) {
2065 synchronized (mutex) {return c.contains(o);}
2066 }
2067 public Object[] toArray() {
2068 synchronized (mutex) {return c.toArray();}
2069 }
2070 public <T> T[] toArray(T[] a) {
2071 synchronized (mutex) {return c.toArray(a);}
2072 }
2073
2074 public Iterator<E> iterator() {
2075 return c.iterator(); // Must be manually synched by user!
2076 }
2077
2078 public boolean add(E e) {
2079 synchronized (mutex) {return c.add(e);}
2080 }
2081 public boolean remove(Object o) {
2082 synchronized (mutex) {return c.remove(o);}
2083 }
2084
2085 public boolean containsAll(Collection<?> coll) {
2086 synchronized (mutex) {return c.containsAll(coll);}
2087 }
2088 public boolean addAll(Collection<? extends E> coll) {
2089 synchronized (mutex) {return c.addAll(coll);}
2090 }
2091 public boolean removeAll(Collection<?> coll) {
2092 synchronized (mutex) {return c.removeAll(coll);}
2093 }
2094 public boolean retainAll(Collection<?> coll) {
2095 synchronized (mutex) {return c.retainAll(coll);}
2096 }
2097 public void clear() {
2098 synchronized (mutex) {c.clear();}
2099 }
2100 public String toString() {
2101 synchronized (mutex) {return c.toString();}
2102 }
2103 // Override default methods in Collection
2104 @Override
2105 public void forEach(Consumer<? super E> consumer) {
2106 synchronized (mutex) {c.forEach(consumer);}
2107 }
2108 @Override
2109 public boolean removeIf(Predicate<? super E> filter) {
2110 synchronized (mutex) {return c.removeIf(filter);}
2111 }
2112 @Override
2113 public Spliterator<E> spliterator() {
2114 return c.spliterator(); // Must be manually synched by user!
2115 }
2116 private void writeObject(ObjectOutputStream s) throws IOException {
2117 synchronized (mutex) {s.defaultWriteObject();}
2118 }
2119 }
2120
2121 /**
2122 * Returns a synchronized (thread-safe) set backed by the specified
2123 * set. In order to guarantee serial access, it is critical that
2124 * <strong>all</strong> access to the backing set is accomplished
2125 * through the returned set.<p>
2126 *
2127 * It is imperative that the user manually synchronize on the returned
2128 * set when iterating over it:
2129 * <pre>
2130 * Set s = Collections.synchronizedSet(new HashSet());
2131 * ...
2132 * synchronized (s) {
2133 * Iterator i = s.iterator(); // Must be in the synchronized block
2134 * while (i.hasNext())
2135 * foo(i.next());
2136 * }
2137 * </pre>
2138 * Failure to follow this advice may result in non-deterministic behavior.
2139 *
2140 * <p>The returned set will be serializable if the specified set is
2141 * serializable.
2142 *
2143 * @param <T> the class of the objects in the set
2144 * @param s the set to be "wrapped" in a synchronized set.
2145 * @return a synchronized view of the specified set.
2146 */
2147 public static <T> Set<T> synchronizedSet(Set<T> s) {
2148 return new SynchronizedSet<>(s);
2149 }
2150
2151 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
2152 return new SynchronizedSet<>(s, mutex);
2153 }
2154
2155 /**
2156 * @serial include
2157 */
2158 static class SynchronizedSet<E>
2159 extends SynchronizedCollection<E>
2160 implements Set<E> {
2161 private static final long serialVersionUID = 487447009682186044L;
2162
2163 SynchronizedSet(Set<E> s) {
2164 super(s);
2165 }
2166 SynchronizedSet(Set<E> s, Object mutex) {
2167 super(s, mutex);
2168 }
2169
2170 public boolean equals(Object o) {
2171 if (this == o)
2172 return true;
2173 synchronized (mutex) {return c.equals(o);}
2174 }
2175 public int hashCode() {
2176 synchronized (mutex) {return c.hashCode();}
2177 }
2178 }
2179
2180 /**
2181 * Returns a synchronized (thread-safe) sorted set backed by the specified
2182 * sorted set. In order to guarantee serial access, it is critical that
2183 * <strong>all</strong> access to the backing sorted set is accomplished
2184 * through the returned sorted set (or its views).<p>
2185 *
2186 * It is imperative that the user manually synchronize on the returned
2187 * sorted set when iterating over it or any of its <tt>subSet</tt>,
2188 * <tt>headSet</tt>, or <tt>tailSet</tt> views.
2189 * <pre>
2190 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2191 * ...
2192 * synchronized (s) {
2193 * Iterator i = s.iterator(); // Must be in the synchronized block
2194 * while (i.hasNext())
2195 * foo(i.next());
2196 * }
2197 * </pre>
2198 * or:
2199 * <pre>
2200 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2201 * SortedSet s2 = s.headSet(foo);
2202 * ...
2203 * synchronized (s) { // Note: s, not s2!!!
2204 * Iterator i = s2.iterator(); // Must be in the synchronized block
2205 * while (i.hasNext())
2206 * foo(i.next());
2207 * }
2208 * </pre>
2209 * Failure to follow this advice may result in non-deterministic behavior.
2210 *
2211 * <p>The returned sorted set will be serializable if the specified
2212 * sorted set is serializable.
2213 *
2214 * @param <T> the class of the objects in the set
2215 * @param s the sorted set to be "wrapped" in a synchronized sorted set.
2216 * @return a synchronized view of the specified sorted set.
2217 */
2218 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
2219 return new SynchronizedSortedSet<>(s);
2220 }
2221
2222 /**
2223 * @serial include
2224 */
2225 static class SynchronizedSortedSet<E>
2226 extends SynchronizedSet<E>
2227 implements SortedSet<E>
2228 {
2229 private static final long serialVersionUID = 8695801310862127406L;
2230
2231 private final SortedSet<E> ss;
2232
2233 SynchronizedSortedSet(SortedSet<E> s) {
2234 super(s);
2235 ss = s;
2236 }
2237 SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
2238 super(s, mutex);
2239 ss = s;
2240 }
2241
2242 public Comparator<? super E> comparator() {
2243 synchronized (mutex) {return ss.comparator();}
2244 }
2245
2246 public SortedSet<E> subSet(E fromElement, E toElement) {
2247 synchronized (mutex) {
2248 return new SynchronizedSortedSet<>(
2249 ss.subSet(fromElement, toElement), mutex);
2250 }
2251 }
2252 public SortedSet<E> headSet(E toElement) {
2253 synchronized (mutex) {
2254 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
2255 }
2256 }
2257 public SortedSet<E> tailSet(E fromElement) {
2258 synchronized (mutex) {
2259 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
2260 }
2261 }
2262
2263 public E first() {
2264 synchronized (mutex) {return ss.first();}
2265 }
2266 public E last() {
2267 synchronized (mutex) {return ss.last();}
2268 }
2269 }
2270
2271 /**
2272 * Returns a synchronized (thread-safe) navigable set backed by the
2273 * specified navigable set. In order to guarantee serial access, it is
2274 * critical that <strong>all</strong> access to the backing navigable set is
2275 * accomplished through the returned navigable set (or its views).<p>
2276 *
2277 * It is imperative that the user manually synchronize on the returned
2278 * navigable set when iterating over it or any of its {@code subSet},
2279 * {@code headSet}, or {@code tailSet} views.
2280 * <pre>
2281 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
2282 * ...
2283 * synchronized (s) {
2284 * Iterator i = s.iterator(); // Must be in the synchronized block
2285 * while (i.hasNext())
2286 * foo(i.next());
2287 * }
2288 * </pre>
2289 * or:
2290 * <pre>
2291 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
2292 * NavigableSet s2 = s.headSet(foo, true);
2293 * ...
2294 * synchronized (s) { // Note: s, not s2!!!
2295 * Iterator i = s2.iterator(); // Must be in the synchronized block
2296 * while (i.hasNext())
2297 * foo(i.next());
2298 * }
2299 * </pre>
2300 * Failure to follow this advice may result in non-deterministic behavior.
2301 *
2302 * <p>The returned navigable set will be serializable if the specified
2303 * navigable set is serializable.
2304 *
2305 * @param <T> the class of the objects in the set
2306 * @param s the navigable set to be "wrapped" in a synchronized navigable
2307 * set
2308 * @return a synchronized view of the specified navigable set
2309 * @since 1.8
2310 */
2311 public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) {
2312 return new SynchronizedNavigableSet<>(s);
2313 }
2314
2315 /**
2316 * @serial include
2317 */
2318 static class SynchronizedNavigableSet<E>
2319 extends SynchronizedSortedSet<E>
2320 implements NavigableSet<E>
2321 {
2322 private static final long serialVersionUID = -5505529816273629798L;
2323
2324 private final NavigableSet<E> ns;
2325
2326 SynchronizedNavigableSet(NavigableSet<E> s) {
2327 super(s);
2328 ns = s;
2329 }
2330
2331 SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) {
2332 super(s, mutex);
2333 ns = s;
2334 }
2335 public E lower(E e) { synchronized (mutex) {return ns.lower(e);} }
2336 public E floor(E e) { synchronized (mutex) {return ns.floor(e);} }
2337 public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} }
2338 public E higher(E e) { synchronized (mutex) {return ns.higher(e);} }
2339 public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} }
2340 public E pollLast() { synchronized (mutex) {return ns.pollLast();} }
2341
2342 public NavigableSet<E> descendingSet() {
2343 synchronized (mutex) {
2344 return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex);
2345 }
2346 }
2347
2348 public Iterator<E> descendingIterator()
2349 { synchronized (mutex) { return descendingSet().iterator(); } }
2350
2351 public NavigableSet<E> subSet(E fromElement, E toElement) {
2352 synchronized (mutex) {
2353 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex);
2354 }
2355 }
2356 public NavigableSet<E> headSet(E toElement) {
2357 synchronized (mutex) {
2358 return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex);
2359 }
2360 }
2361 public NavigableSet<E> tailSet(E fromElement) {
2362 synchronized (mutex) {
2363 return new SynchronizedNavigableSet(ns.tailSet(fromElement, true), mutex);
2364 }
2365 }
2366
2367 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
2368 synchronized (mutex) {
2369 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex);
2370 }
2371 }
2372
2373 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
2374 synchronized (mutex) {
2375 return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex);
2376 }
2377 }
2378
2379 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
2380 synchronized (mutex) {
2381 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive));
2382 }
2383 }
2384 }
2385
2386 /**
2387 * Returns a synchronized (thread-safe) list backed by the specified
2388 * list. In order to guarantee serial access, it is critical that
2389 * <strong>all</strong> access to the backing list is accomplished
2390 * through the returned list.<p>
2391 *
2392 * It is imperative that the user manually synchronize on the returned
2393 * list when iterating over it:
2394 * <pre>
2395 * List list = Collections.synchronizedList(new ArrayList());
2396 * ...
2397 * synchronized (list) {
2398 * Iterator i = list.iterator(); // Must be in synchronized block
2399 * while (i.hasNext())
2400 * foo(i.next());
2401 * }
2402 * </pre>
2403 * Failure to follow this advice may result in non-deterministic behavior.
2404 *
2405 * <p>The returned list will be serializable if the specified list is
2406 * serializable.
2407 *
2408 * @param <T> the class of the objects in the list
2409 * @param list the list to be "wrapped" in a synchronized list.
2410 * @return a synchronized view of the specified list.
2411 */
2412 public static <T> List<T> synchronizedList(List<T> list) {
2413 return (list instanceof RandomAccess ?
2414 new SynchronizedRandomAccessList<>(list) :
2415 new SynchronizedList<>(list));
2416 }
2417
2418 static <T> List<T> synchronizedList(List<T> list, Object mutex) {
2419 return (list instanceof RandomAccess ?
2420 new SynchronizedRandomAccessList<>(list, mutex) :
2421 new SynchronizedList<>(list, mutex));
2422 }
2423
2424 /**
2425 * @serial include
2426 */
2427 static class SynchronizedList<E>
2428 extends SynchronizedCollection<E>
2429 implements List<E> {
2430 private static final long serialVersionUID = -7754090372962971524L;
2431
2432 final List<E> list;
2433
2434 SynchronizedList(List<E> list) {
2435 super(list);
2436 this.list = list;
2437 }
2438 SynchronizedList(List<E> list, Object mutex) {
2439 super(list, mutex);
2440 this.list = list;
2441 }
2442
2443 public boolean equals(Object o) {
2444 if (this == o)
2445 return true;
2446 synchronized (mutex) {return list.equals(o);}
2447 }
2448 public int hashCode() {
2449 synchronized (mutex) {return list.hashCode();}
2450 }
2451
2452 public E get(int index) {
2453 synchronized (mutex) {return list.get(index);}
2454 }
2455 public E set(int index, E element) {
2456 synchronized (mutex) {return list.set(index, element);}
2457 }
2458 public void add(int index, E element) {
2459 synchronized (mutex) {list.add(index, element);}
2460 }
2461 public E remove(int index) {
2462 synchronized (mutex) {return list.remove(index);}
2463 }
2464
2465 public int indexOf(Object o) {
2466 synchronized (mutex) {return list.indexOf(o);}
2467 }
2468 public int lastIndexOf(Object o) {
2469 synchronized (mutex) {return list.lastIndexOf(o);}
2470 }
2471
2472 public boolean addAll(int index, Collection<? extends E> c) {
2473 synchronized (mutex) {return list.addAll(index, c);}
2474 }
2475
2476 public ListIterator<E> listIterator() {
2477 return list.listIterator(); // Must be manually synched by user
2478 }
2479
2480 public ListIterator<E> listIterator(int index) {
2481 return list.listIterator(index); // Must be manually synched by user
2482 }
2483
2484 public List<E> subList(int fromIndex, int toIndex) {
2485 synchronized (mutex) {
2486 return new SynchronizedList<>(list.subList(fromIndex, toIndex),
2487 mutex);
2488 }
2489 }
2490
2491 @Override
2492 public void replaceAll(UnaryOperator<E> operator) {
2493 synchronized (mutex) {list.replaceAll(operator);}
2494 }
2495 @Override
2496 public void sort(Comparator<? super E> c) {
2497 synchronized (mutex) {list.sort(c);}
2498 }
2499
2500 /**
2501 * SynchronizedRandomAccessList instances are serialized as
2502 * SynchronizedList instances to allow them to be deserialized
2503 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
2504 * This method inverts the transformation. As a beneficial
2505 * side-effect, it also grafts the RandomAccess marker onto
2506 * SynchronizedList instances that were serialized in pre-1.4 JREs.
2507 *
2508 * Note: Unfortunately, SynchronizedRandomAccessList instances
2509 * serialized in 1.4.1 and deserialized in 1.4 will become
2510 * SynchronizedList instances, as this method was missing in 1.4.
2511 */
2512 private Object readResolve() {
2513 return (list instanceof RandomAccess
2514 ? new SynchronizedRandomAccessList<>(list)
2515 : this);
2516 }
2517 }
2518
2519 /**
2520 * @serial include
2521 */
2522 static class SynchronizedRandomAccessList<E>
2523 extends SynchronizedList<E>
2524 implements RandomAccess {
2525
2526 SynchronizedRandomAccessList(List<E> list) {
2527 super(list);
2528 }
2529
2530 SynchronizedRandomAccessList(List<E> list, Object mutex) {
2531 super(list, mutex);
2532 }
2533
2534 public List<E> subList(int fromIndex, int toIndex) {
2535 synchronized (mutex) {
2536 return new SynchronizedRandomAccessList<>(
2537 list.subList(fromIndex, toIndex), mutex);
2538 }
2539 }
2540
2541 private static final long serialVersionUID = 1530674583602358482L;
2542
2543 /**
2544 * Allows instances to be deserialized in pre-1.4 JREs (which do
2545 * not have SynchronizedRandomAccessList). SynchronizedList has
2546 * a readResolve method that inverts this transformation upon
2547 * deserialization.
2548 */
2549 private Object writeReplace() {
2550 return new SynchronizedList<>(list);
2551 }
2552 }
2553
2554 /**
2555 * Returns a synchronized (thread-safe) map backed by the specified
2556 * map. In order to guarantee serial access, it is critical that
2557 * <strong>all</strong> access to the backing map is accomplished
2558 * through the returned map.<p>
2559 *
2560 * It is imperative that the user manually synchronize on the returned
2561 * map when iterating over any of its collection views:
2562 * <pre>
2563 * Map m = Collections.synchronizedMap(new HashMap());
2564 * ...
2565 * Set s = m.keySet(); // Needn't be in synchronized block
2566 * ...
2567 * synchronized (m) { // Synchronizing on m, not s!
2568 * Iterator i = s.iterator(); // Must be in synchronized block
2569 * while (i.hasNext())
2570 * foo(i.next());
2571 * }
2572 * </pre>
2573 * Failure to follow this advice may result in non-deterministic behavior.
2574 *
2575 * <p>The returned map will be serializable if the specified map is
2576 * serializable.
2577 *
2578 * @param <K> the class of the map keys
2579 * @param <V> the class of the map values
2580 * @param m the map to be "wrapped" in a synchronized map.
2581 * @return a synchronized view of the specified map.
2582 */
2583 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
2584 return new SynchronizedMap<>(m);
2585 }
2586
2587 /**
2588 * @serial include
2589 */
2590 private static class SynchronizedMap<K,V>
2591 implements Map<K,V>, Serializable {
2592 private static final long serialVersionUID = 1978198479659022715L;
2593
2594 private final Map<K,V> m; // Backing Map
2595 final Object mutex; // Object on which to synchronize
2596
2597 SynchronizedMap(Map<K,V> m) {
2598 this.m = Objects.requireNonNull(m);
2599 mutex = this;
2600 }
2601
2602 SynchronizedMap(Map<K,V> m, Object mutex) {
2603 this.m = m;
2604 this.mutex = mutex;
2605 }
2606
2607 public int size() {
2608 synchronized (mutex) {return m.size();}
2609 }
2610 public boolean isEmpty() {
2611 synchronized (mutex) {return m.isEmpty();}
2612 }
2613 public boolean containsKey(Object key) {
2614 synchronized (mutex) {return m.containsKey(key);}
2615 }
2616 public boolean containsValue(Object value) {
2617 synchronized (mutex) {return m.containsValue(value);}
2618 }
2619 public V get(Object key) {
2620 synchronized (mutex) {return m.get(key);}
2621 }
2622
2623 public V put(K key, V value) {
2624 synchronized (mutex) {return m.put(key, value);}
2625 }
2626 public V remove(Object key) {
2627 synchronized (mutex) {return m.remove(key);}
2628 }
2629 public void putAll(Map<? extends K, ? extends V> map) {
2630 synchronized (mutex) {m.putAll(map);}
2631 }
2632 public void clear() {
2633 synchronized (mutex) {m.clear();}
2634 }
2635
2636 private transient Set<K> keySet = null;
2637 private transient Set<Map.Entry<K,V>> entrySet = null;
2638 private transient Collection<V> values = null;
2639
2640 public Set<K> keySet() {
2641 synchronized (mutex) {
2642 if (keySet==null)
2643 keySet = new SynchronizedSet<>(m.keySet(), mutex);
2644 return keySet;
2645 }
2646 }
2647
2648 public Set<Map.Entry<K,V>> entrySet() {
2649 synchronized (mutex) {
2650 if (entrySet==null)
2651 entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
2652 return entrySet;
2653 }
2654 }
2655
2656 public Collection<V> values() {
2657 synchronized (mutex) {
2658 if (values==null)
2659 values = new SynchronizedCollection<>(m.values(), mutex);
2660 return values;
2661 }
2662 }
2663
2664 public boolean equals(Object o) {
2665 if (this == o)
2666 return true;
2667 synchronized (mutex) {return m.equals(o);}
2668 }
2669 public int hashCode() {
2670 synchronized (mutex) {return m.hashCode();}
2671 }
2672 public String toString() {
2673 synchronized (mutex) {return m.toString();}
2674 }
2675
2676 // Override default methods in Map
2677 @Override
2678 public V getOrDefault(Object k, V defaultValue) {
2679 synchronized (mutex) {return m.getOrDefault(k, defaultValue);}
2680 }
2681 @Override
2682 public void forEach(BiConsumer<? super K, ? super V> action) {
2683 synchronized (mutex) {m.forEach(action);}
2684 }
2685 @Override
2686 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
2687 synchronized (mutex) {m.replaceAll(function);}
2688 }
2689 @Override
2690 public V putIfAbsent(K key, V value) {
2691 synchronized (mutex) {return m.putIfAbsent(key, value);}
2692 }
2693 @Override
2694 public boolean remove(Object key, Object value) {
2695 synchronized (mutex) {return m.remove(key, value);}
2696 }
2697 @Override
2698 public boolean replace(K key, V oldValue, V newValue) {
2699 synchronized (mutex) {return m.replace(key, oldValue, newValue);}
2700 }
2701 @Override
2702 public V replace(K key, V value) {
2703 synchronized (mutex) {return m.replace(key, value);}
2704 }
2705 @Override
2706 public V computeIfAbsent(K key,
2707 Function<? super K, ? extends V> mappingFunction) {
2708 synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);}
2709 }
2710 @Override
2711 public V computeIfPresent(K key,
2712 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2713 synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);}
2714 }
2715 @Override
2716 public V compute(K key,
2717 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2718 synchronized (mutex) {return m.compute(key, remappingFunction);}
2719 }
2720 @Override
2721 public V merge(K key, V value,
2722 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
2723 synchronized (mutex) {return m.merge(key, value, remappingFunction);}
2724 }
2725
2726 private void writeObject(ObjectOutputStream s) throws IOException {
2727 synchronized (mutex) {s.defaultWriteObject();}
2728 }
2729 }
2730
2731 /**
2732 * Returns a synchronized (thread-safe) sorted map backed by the specified
2733 * sorted map. In order to guarantee serial access, it is critical that
2734 * <strong>all</strong> access to the backing sorted map is accomplished
2735 * through the returned sorted map (or its views).<p>
2736 *
2737 * It is imperative that the user manually synchronize on the returned
2738 * sorted map when iterating over any of its collection views, or the
2739 * collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or
2740 * <tt>tailMap</tt> views.
2741 * <pre>
2742 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2743 * ...
2744 * Set s = m.keySet(); // Needn't be in synchronized block
2745 * ...
2746 * synchronized (m) { // Synchronizing on m, not s!
2747 * Iterator i = s.iterator(); // Must be in synchronized block
2748 * while (i.hasNext())
2749 * foo(i.next());
2750 * }
2751 * </pre>
2752 * or:
2753 * <pre>
2754 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2755 * SortedMap m2 = m.subMap(foo, bar);
2756 * ...
2757 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2758 * ...
2759 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2760 * Iterator i = s.iterator(); // Must be in synchronized block
2761 * while (i.hasNext())
2762 * foo(i.next());
2763 * }
2764 * </pre>
2765 * Failure to follow this advice may result in non-deterministic behavior.
2766 *
2767 * <p>The returned sorted map will be serializable if the specified
2768 * sorted map is serializable.
2769 *
2770 * @param <K> the class of the map keys
2771 * @param <V> the class of the map values
2772 * @param m the sorted map to be "wrapped" in a synchronized sorted map.
2773 * @return a synchronized view of the specified sorted map.
2774 */
2775 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
2776 return new SynchronizedSortedMap<>(m);
2777 }
2778
2779 /**
2780 * @serial include
2781 */
2782 static class SynchronizedSortedMap<K,V>
2783 extends SynchronizedMap<K,V>
2784 implements SortedMap<K,V>
2785 {
2786 private static final long serialVersionUID = -8798146769416483793L;
2787
2788 private final SortedMap<K,V> sm;
2789
2790 SynchronizedSortedMap(SortedMap<K,V> m) {
2791 super(m);
2792 sm = m;
2793 }
2794 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
2795 super(m, mutex);
2796 sm = m;
2797 }
2798
2799 public Comparator<? super K> comparator() {
2800 synchronized (mutex) {return sm.comparator();}
2801 }
2802
2803 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2804 synchronized (mutex) {
2805 return new SynchronizedSortedMap<>(
2806 sm.subMap(fromKey, toKey), mutex);
2807 }
2808 }
2809 public SortedMap<K,V> headMap(K toKey) {
2810 synchronized (mutex) {
2811 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
2812 }
2813 }
2814 public SortedMap<K,V> tailMap(K fromKey) {
2815 synchronized (mutex) {
2816 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
2817 }
2818 }
2819
2820 public K firstKey() {
2821 synchronized (mutex) {return sm.firstKey();}
2822 }
2823 public K lastKey() {
2824 synchronized (mutex) {return sm.lastKey();}
2825 }
2826 }
2827
2828 /**
2829 * Returns a synchronized (thread-safe) navigable map backed by the
2830 * specified navigable map. In order to guarantee serial access, it is
2831 * critical that <strong>all</strong> access to the backing navigable map is
2832 * accomplished through the returned navigable map (or its views).<p>
2833 *
2834 * It is imperative that the user manually synchronize on the returned
2835 * navigable map when iterating over any of its collection views, or the
2836 * collections views of any of its {@code subMap}, {@code headMap} or
2837 * {@code tailMap} views.
2838 * <pre>
2839 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
2840 * ...
2841 * Set s = m.keySet(); // Needn't be in synchronized block
2842 * ...
2843 * synchronized (m) { // Synchronizing on m, not s!
2844 * Iterator i = s.iterator(); // Must be in synchronized block
2845 * while (i.hasNext())
2846 * foo(i.next());
2847 * }
2848 * </pre>
2849 * or:
2850 * <pre>
2851 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
2852 * NavigableMap m2 = m.subMap(foo, true, bar, false);
2853 * ...
2854 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2855 * ...
2856 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2857 * Iterator i = s.iterator(); // Must be in synchronized block
2858 * while (i.hasNext())
2859 * foo(i.next());
2860 * }
2861 * </pre>
2862 * Failure to follow this advice may result in non-deterministic behavior.
2863 *
2864 * <p>The returned navigable map will be serializable if the specified
2865 * navigable map is serializable.
2866 *
2867 * @param <K> the class of the map keys
2868 * @param <V> the class of the map values
2869 * @param m the navigable map to be "wrapped" in a synchronized navigable
2870 * map
2871 * @return a synchronized view of the specified navigable map.
2872 * @since 1.8
2873 */
2874 public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) {
2875 return new SynchronizedNavigableMap<>(m);
2876 }
2877
2878 /**
2879 * A synchronized NavigableMap.
2880 *
2881 * @serial include
2882 */
2883 static class SynchronizedNavigableMap<K,V>
2884 extends SynchronizedSortedMap<K,V>
2885 implements NavigableMap<K,V>
2886 {
2887 private static final long serialVersionUID = 699392247599746807L;
2888
2889 private final NavigableMap<K,V> nm;
2890
2891 SynchronizedNavigableMap(NavigableMap<K,V> m) {
2892 super(m);
2893 nm = m;
2894 }
2895 SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) {
2896 super(m, mutex);
2897 nm = m;
2898 }
2899
2900 public Entry<K, V> lowerEntry(K key)
2901 { synchronized (mutex) { return nm.lowerEntry(key); } }
2902 public K lowerKey(K key)
2903 { synchronized (mutex) { return nm.lowerKey(key); } }
2904 public Entry<K, V> floorEntry(K key)
2905 { synchronized (mutex) { return nm.floorEntry(key); } }
2906 public K floorKey(K key)
2907 { synchronized (mutex) { return nm.floorKey(key); } }
2908 public Entry<K, V> ceilingEntry(K key)
2909 { synchronized (mutex) { return nm.ceilingEntry(key); } }
2910 public K ceilingKey(K key)
2911 { synchronized (mutex) { return nm.ceilingKey(key); } }
2912 public Entry<K, V> higherEntry(K key)
2913 { synchronized (mutex) { return nm.higherEntry(key); } }
2914 public K higherKey(K key)
2915 { synchronized (mutex) { return nm.higherKey(key); } }
2916 public Entry<K, V> firstEntry()
2917 { synchronized (mutex) { return nm.firstEntry(); } }
2918 public Entry<K, V> lastEntry()
2919 { synchronized (mutex) { return nm.lastEntry(); } }
2920 public Entry<K, V> pollFirstEntry()
2921 { synchronized (mutex) { return nm.pollFirstEntry(); } }
2922 public Entry<K, V> pollLastEntry()
2923 { synchronized (mutex) { return nm.pollLastEntry(); } }
2924
2925 public NavigableMap<K, V> descendingMap() {
2926 synchronized (mutex) {
2927 return
2928 new SynchronizedNavigableMap(nm.descendingMap(), mutex);
2929 }
2930 }
2931
2932 public NavigableSet<K> keySet() {
2933 return navigableKeySet();
2934 }
2935
2936 public NavigableSet<K> navigableKeySet() {
2937 synchronized (mutex) {
2938 return new SynchronizedNavigableSet(nm.navigableKeySet(), mutex);
2939 }
2940 }
2941
2942 public NavigableSet<K> descendingKeySet() {
2943 synchronized (mutex) {
2944 return new SynchronizedNavigableSet(nm.descendingKeySet(), mutex);
2945 }
2946 }
2947
2948
2949 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2950 synchronized (mutex) {
2951 return new SynchronizedNavigableMap<>(
2952 nm.subMap(fromKey, true, toKey, false), mutex);
2953 }
2954 }
2955 public SortedMap<K,V> headMap(K toKey) {
2956 synchronized (mutex) {
2957 return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex);
2958 }
2959 }
2960 public SortedMap<K,V> tailMap(K fromKey) {
2961 synchronized (mutex) {
2962 return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex);
2963 }
2964 }
2965
2966 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
2967 synchronized (mutex) {
2968 return new SynchronizedNavigableMap(
2969 nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex);
2970 }
2971 }
2972
2973 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
2974 synchronized (mutex) {
2975 return new SynchronizedNavigableMap(
2976 nm.headMap(toKey, inclusive), mutex);
2977 }
2978 }
2979
2980 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
2981 synchronized (mutex) {
2982 return new SynchronizedNavigableMap(
2983 nm.tailMap(fromKey, inclusive), mutex);
2984 }
2985 }
2986 }
2987
2988 // Dynamically typesafe collection wrappers
2989
2990 /**
2991 * Returns a dynamically typesafe view of the specified collection.
2992 * Any attempt to insert an element of the wrong type will result in an
2993 * immediate {@link ClassCastException}. Assuming a collection
2994 * contains no incorrectly typed elements prior to the time a
2995 * dynamically typesafe view is generated, and that all subsequent
2996 * access to the collection takes place through the view, it is
2997 * <i>guaranteed</i> that the collection cannot contain an incorrectly
2998 * typed element.
2999 *
3000 * <p>The generics mechanism in the language provides compile-time
3001 * (static) type checking, but it is possible to defeat this mechanism
3002 * with unchecked casts. Usually this is not a problem, as the compiler
3003 * issues warnings on all such unchecked operations. There are, however,
3004 * times when static type checking alone is not sufficient. For example,
3005 * suppose a collection is passed to a third-party library and it is
3006 * imperative that the library code not corrupt the collection by
3007 * inserting an element of the wrong type.
3008 *
3009 * <p>Another use of dynamically typesafe views is debugging. Suppose a
3010 * program fails with a {@code ClassCastException}, indicating that an
3011 * incorrectly typed element was put into a parameterized collection.
3012 * Unfortunately, the exception can occur at any time after the erroneous
3013 * element is inserted, so it typically provides little or no information
3014 * as to the real source of the problem. If the problem is reproducible,
3015 * one can quickly determine its source by temporarily modifying the
3016 * program to wrap the collection with a dynamically typesafe view.
3017 * For example, this declaration:
3018 * <pre> {@code
3019 * Collection<String> c = new HashSet<>();
3020 * }</pre>
3021 * may be replaced temporarily by this one:
3022 * <pre> {@code
3023 * Collection<String> c = Collections.checkedCollection(
3024 * new HashSet<>(), String.class);
3025 * }</pre>
3026 * Running the program again will cause it to fail at the point where
3027 * an incorrectly typed element is inserted into the collection, clearly
3028 * identifying the source of the problem. Once the problem is fixed, the
3029 * modified declaration may be reverted back to the original.
3030 *
3031 * <p>The returned collection does <i>not</i> pass the hashCode and equals
3032 * operations through to the backing collection, but relies on
3033 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
3034 * is necessary to preserve the contracts of these operations in the case
3035 * that the backing collection is a set or a list.
3036 *
3037 * <p>The returned collection will be serializable if the specified
3038 * collection is serializable.
3039 *
3040 * <p>Since {@code null} is considered to be a value of any reference
3041 * type, the returned collection permits insertion of null elements
3042 * whenever the backing collection does.
3043 *
3044 * @param <E> the class of the objects in the collection
3045 * @param c the collection for which a dynamically typesafe view is to be
3046 * returned
3047 * @param type the type of element that {@code c} is permitted to hold
3048 * @return a dynamically typesafe view of the specified collection
3049 * @since 1.5
3050 */
3051 public static <E> Collection<E> checkedCollection(Collection<E> c,
3052 Class<E> type) {
3053 return new CheckedCollection<>(c, type);
3054 }
3055
3056 @SuppressWarnings("unchecked")
3057 static <T> T[] zeroLengthArray(Class<T> type) {
3058 return (T[]) Array.newInstance(type, 0);
3059 }
3060
3061 /**
3062 * @serial include
3063 */
3064 static class CheckedCollection<E> implements Collection<E>, Serializable {
3065 private static final long serialVersionUID = 1578914078182001775L;
3066
3067 final Collection<E> c;
3068 final Class<E> type;
3069
3070 void typeCheck(Object o) {
3071 if (o != null && !type.isInstance(o))
3072 throw new ClassCastException(badElementMsg(o));
3073 }
3074
3075 private String badElementMsg(Object o) {
3076 return "Attempt to insert " + o.getClass() +
3077 " element into collection with element type " + type;
3078 }
3079
3080 CheckedCollection(Collection<E> c, Class<E> type) {
3081 if (c==null || type == null)
3082 throw new NullPointerException();
3083 this.c = c;
3084 this.type = type;
3085 }
3086
3087 public int size() { return c.size(); }
3088 public boolean isEmpty() { return c.isEmpty(); }
3089 public boolean contains(Object o) { return c.contains(o); }
3090 public Object[] toArray() { return c.toArray(); }
3091 public <T> T[] toArray(T[] a) { return c.toArray(a); }
3092 public String toString() { return c.toString(); }
3093 public boolean remove(Object o) { return c.remove(o); }
3094 public void clear() { c.clear(); }
3095
3096 public boolean containsAll(Collection<?> coll) {
3097 return c.containsAll(coll);
3098 }
3099 public boolean removeAll(Collection<?> coll) {
3100 return c.removeAll(coll);
3101 }
3102 public boolean retainAll(Collection<?> coll) {
3103 return c.retainAll(coll);
3104 }
3105
3106 public Iterator<E> iterator() {
3107 // JDK-6363904 - unwrapped iterator could be typecast to
3108 // ListIterator with unsafe set()
3109 final Iterator<E> it = c.iterator();
3110 return new Iterator<E>() {
3111 public boolean hasNext() { return it.hasNext(); }
3112 public E next() { return it.next(); }
3113 public void remove() { it.remove(); }};
3114 }
3115
3116 public boolean add(E e) {
3117 typeCheck(e);
3118 return c.add(e);
3119 }
3120
3121 private E[] zeroLengthElementArray = null; // Lazily initialized
3122
3123 private E[] zeroLengthElementArray() {
3124 return zeroLengthElementArray != null ? zeroLengthElementArray :
3125 (zeroLengthElementArray = zeroLengthArray(type));
3126 }
3127
3128 @SuppressWarnings("unchecked")
3129 Collection<E> checkedCopyOf(Collection<? extends E> coll) {
3130 Object[] a = null;
3131 try {
3132 E[] z = zeroLengthElementArray();
3133 a = coll.toArray(z);
3134 // Defend against coll violating the toArray contract
3135 if (a.getClass() != z.getClass())
3136 a = Arrays.copyOf(a, a.length, z.getClass());
3137 } catch (ArrayStoreException ignore) {
3138 // To get better and consistent diagnostics,
3139 // we call typeCheck explicitly on each element.
3140 // We call clone() to defend against coll retaining a
3141 // reference to the returned array and storing a bad
3142 // element into it after it has been type checked.
3143 a = coll.toArray().clone();
3144 for (Object o : a)
3145 typeCheck(o);
3146 }
3147 // A slight abuse of the type system, but safe here.
3148 return (Collection<E>) Arrays.asList(a);
3149 }
3150
3151 public boolean addAll(Collection<? extends E> coll) {
3152 // Doing things this way insulates us from concurrent changes
3153 // in the contents of coll and provides all-or-nothing
3154 // semantics (which we wouldn't get if we type-checked each
3155 // element as we added it)
3156 return c.addAll(checkedCopyOf(coll));
3157 }
3158
3159 // Override default methods in Collection
3160 @Override
3161 public void forEach(Consumer<? super E> action) {c.forEach(action);}
3162 @Override
3163 public boolean removeIf(Predicate<? super E> filter) {
3164 return c.removeIf(filter);
3165 }
3166 @Override
3167 public Spliterator<E> spliterator() {return c.spliterator();}
3168 }
3169
3170 /**
3171 * Returns a dynamically typesafe view of the specified queue.
3172 * Any attempt to insert an element of the wrong type will result in
3173 * an immediate {@link ClassCastException}. Assuming a queue contains
3174 * no incorrectly typed elements prior to the time a dynamically typesafe
3175 * view is generated, and that all subsequent access to the queue
3176 * takes place through the view, it is <i>guaranteed</i> that the
3177 * queue cannot contain an incorrectly typed element.
3178 *
3179 * <p>A discussion of the use of dynamically typesafe views may be
3180 * found in the documentation for the {@link #checkedCollection
3181 * checkedCollection} method.
3182 *
3183 * <p>The returned queue will be serializable if the specified queue
3184 * is serializable.
3185 *
3186 * <p>Since {@code null} is considered to be a value of any reference
3187 * type, the returned queue permits insertion of {@code null} elements
3188 * whenever the backing queue does.
3189 *
3190 * @param <E> the class of the objects in the queue
3191 * @param queue the queue for which a dynamically typesafe view is to be
3192 * returned
3193 * @param type the type of element that {@code queue} is permitted to hold
3194 * @return a dynamically typesafe view of the specified queue
3195 * @since 1.8
3196 */
3197 public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) {
3198 return new CheckedQueue<>(queue, type);
3199 }
3200
3201 /**
3202 * @serial include
3203 */
3204 static class CheckedQueue<E>
3205 extends CheckedCollection<E>
3206 implements Queue<E>, Serializable
3207 {
3208 private static final long serialVersionUID = 1433151992604707767L;
3209 final Queue<E> queue;
3210
3211 CheckedQueue(Queue<E> queue, Class<E> elementType) {
3212 super(queue, elementType);
3213 this.queue = queue;
3214 }
3215
3216 public E element() {return queue.element();}
3217 public boolean equals(Object o) {return o == this || c.equals(o);}
3218 public int hashCode() {return c.hashCode();}
3219 public E peek() {return queue.peek();}
3220 public E poll() {return queue.poll();}
3221 public E remove() {return queue.remove();}
3222
3223 public boolean offer(E e) {
3224 typeCheck(e);
3225 return add(e);
3226 }
3227 }
3228
3229 /**
3230 * Returns a dynamically typesafe view of the specified set.
3231 * Any attempt to insert an element of the wrong type will result in
3232 * an immediate {@link ClassCastException}. Assuming a set contains
3233 * no incorrectly typed elements prior to the time a dynamically typesafe
3234 * view is generated, and that all subsequent access to the set
3235 * takes place through the view, it is <i>guaranteed</i> that the
3236 * set cannot contain an incorrectly typed element.
3237 *
3238 * <p>A discussion of the use of dynamically typesafe views may be
3239 * found in the documentation for the {@link #checkedCollection
3240 * checkedCollection} method.
3241 *
3242 * <p>The returned set will be serializable if the specified set is
3243 * serializable.
3244 *
3245 * <p>Since {@code null} is considered to be a value of any reference
3246 * type, the returned set permits insertion of null elements whenever
3247 * the backing set does.
3248 *
3249 * @param <E> the class of the objects in the set
3250 * @param s the set for which a dynamically typesafe view is to be
3251 * returned
3252 * @param type the type of element that {@code s} is permitted to hold
3253 * @return a dynamically typesafe view of the specified set
3254 * @since 1.5
3255 */
3256 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
3257 return new CheckedSet<>(s, type);
3258 }
3259
3260 /**
3261 * @serial include
3262 */
3263 static class CheckedSet<E> extends CheckedCollection<E>
3264 implements Set<E>, Serializable
3265 {
3266 private static final long serialVersionUID = 4694047833775013803L;
3267
3268 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
3269
3270 public boolean equals(Object o) { return o == this || c.equals(o); }
3271 public int hashCode() { return c.hashCode(); }
3272 }
3273
3274 /**
3275 * Returns a dynamically typesafe view of the specified sorted set.
3276 * Any attempt to insert an element of the wrong type will result in an
3277 * immediate {@link ClassCastException}. Assuming a sorted set
3278 * contains no incorrectly typed elements prior to the time a
3279 * dynamically typesafe view is generated, and that all subsequent
3280 * access to the sorted set takes place through the view, it is
3281 * <i>guaranteed</i> that the sorted set cannot contain an incorrectly
3282 * typed element.
3283 *
3284 * <p>A discussion of the use of dynamically typesafe views may be
3285 * found in the documentation for the {@link #checkedCollection
3286 * checkedCollection} method.
3287 *
3288 * <p>The returned sorted set will be serializable if the specified sorted
3289 * set is serializable.
3290 *
3291 * <p>Since {@code null} is considered to be a value of any reference
3292 * type, the returned sorted set permits insertion of null elements
3293 * whenever the backing sorted set does.
3294 *
3295 * @param <E> the class of the objects in the set
3296 * @param s the sorted set for which a dynamically typesafe view is to be
3297 * returned
3298 * @param type the type of element that {@code s} is permitted to hold
3299 * @return a dynamically typesafe view of the specified sorted set
3300 * @since 1.5
3301 */
3302 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
3303 Class<E> type) {
3304 return new CheckedSortedSet<>(s, type);
3305 }
3306
3307 /**
3308 * @serial include
3309 */
3310 static class CheckedSortedSet<E> extends CheckedSet<E>
3311 implements SortedSet<E>, Serializable
3312 {
3313 private static final long serialVersionUID = 1599911165492914959L;
3314
3315 private final SortedSet<E> ss;
3316
3317 CheckedSortedSet(SortedSet<E> s, Class<E> type) {
3318 super(s, type);
3319 ss = s;
3320 }
3321
3322 public Comparator<? super E> comparator() { return ss.comparator(); }
3323 public E first() { return ss.first(); }
3324 public E last() { return ss.last(); }
3325
3326 public SortedSet<E> subSet(E fromElement, E toElement) {
3327 return checkedSortedSet(ss.subSet(fromElement,toElement), type);
3328 }
3329 public SortedSet<E> headSet(E toElement) {
3330 return checkedSortedSet(ss.headSet(toElement), type);
3331 }
3332 public SortedSet<E> tailSet(E fromElement) {
3333 return checkedSortedSet(ss.tailSet(fromElement), type);
3334 }
3335 }
3336
3337 /**
3338 * Returns a dynamically typesafe view of the specified navigable set.
3339 * Any attempt to insert an element of the wrong type will result in an
3340 * immediate {@link ClassCastException}. Assuming a navigable set
3341 * contains no incorrectly typed elements prior to the time a
3342 * dynamically typesafe view is generated, and that all subsequent
3343 * access to the navigable set takes place through the view, it is
3344 * <em>guaranteed</em> that the navigable set cannot contain an incorrectly
3345 * typed element.
3346 *
3347 * <p>A discussion of the use of dynamically typesafe views may be
3348 * found in the documentation for the {@link #checkedCollection
3349 * checkedCollection} method.
3350 *
3351 * <p>The returned navigable set will be serializable if the specified
3352 * navigable set is serializable.
3353 *
3354 * <p>Since {@code null} is considered to be a value of any reference
3355 * type, the returned navigable set permits insertion of null elements
3356 * whenever the backing sorted set does.
3357 *
3358 * @param <E> the class of the objects in the set
3359 * @param s the navigable set for which a dynamically typesafe view is to be
3360 * returned
3361 * @param type the type of element that {@code s} is permitted to hold
3362 * @return a dynamically typesafe view of the specified navigable set
3363 * @since 1.8
3364 */
3365 public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s,
3366 Class<E> type) {
3367 return new CheckedNavigableSet<>(s, type);
3368 }
3369
3370 /**
3371 * @serial include
3372 */
3373 static class CheckedNavigableSet<E> extends CheckedSortedSet<E>
3374 implements NavigableSet<E>, Serializable
3375 {
3376 private static final long serialVersionUID = -5429120189805438922L;
3377
3378 private final NavigableSet<E> ns;
3379
3380 CheckedNavigableSet(NavigableSet<E> s, Class<E> type) {
3381 super(s, type);
3382 ns = s;
3383 }
3384
3385 public E lower(E e) { return ns.lower(e); }
3386 public E floor(E e) { return ns.floor(e); }
3387 public E ceiling(E e) { return ns.ceiling(e); }
3388 public E higher(E e) { return ns.higher(e); }
3389 public E pollFirst() { return ns.pollFirst(); }
3390 public E pollLast() {return ns.pollLast(); }
3391 public NavigableSet<E> descendingSet()
3392 { return checkedNavigableSet(ns.descendingSet(), type); }
3393 public Iterator<E> descendingIterator()
3394 {return checkedNavigableSet(ns.descendingSet(), type).iterator(); }
3395
3396 public NavigableSet<E> subSet(E fromElement, E toElement) {
3397 return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type);
3398 }
3399 public NavigableSet<E> headSet(E toElement) {
3400 return checkedNavigableSet(ns.headSet(toElement, false), type);
3401 }
3402 public NavigableSet<E> tailSet(E fromElement) {
3403 return checkedNavigableSet(ns.tailSet(fromElement, true), type);
3404 }
3405
3406 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
3407 return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type);
3408 }
3409
3410 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
3411 return checkedNavigableSet(ns.headSet(toElement, inclusive), type);
3412 }
3413
3414 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
3415 return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type);
3416 }
3417 }
3418
3419 /**
3420 * Returns a dynamically typesafe view of the specified list.
3421 * Any attempt to insert an element of the wrong type will result in
3422 * an immediate {@link ClassCastException}. Assuming a list contains
3423 * no incorrectly typed elements prior to the time a dynamically typesafe
3424 * view is generated, and that all subsequent access to the list
3425 * takes place through the view, it is <i>guaranteed</i> that the
3426 * list cannot contain an incorrectly typed element.
3427 *
3428 * <p>A discussion of the use of dynamically typesafe views may be
3429 * found in the documentation for the {@link #checkedCollection
3430 * checkedCollection} method.
3431 *
3432 * <p>The returned list will be serializable if the specified list
3433 * is serializable.
3434 *
3435 * <p>Since {@code null} is considered to be a value of any reference
3436 * type, the returned list permits insertion of null elements whenever
3437 * the backing list does.
3438 *
3439 * @param <E> the class of the objects in the list
3440 * @param list the list for which a dynamically typesafe view is to be
3441 * returned
3442 * @param type the type of element that {@code list} is permitted to hold
3443 * @return a dynamically typesafe view of the specified list
3444 * @since 1.5
3445 */
3446 public static <E> List<E> checkedList(List<E> list, Class<E> type) {
3447 return (list instanceof RandomAccess ?
3448 new CheckedRandomAccessList<>(list, type) :
3449 new CheckedList<>(list, type));
3450 }
3451
3452 /**
3453 * @serial include
3454 */
3455 static class CheckedList<E>
3456 extends CheckedCollection<E>
3457 implements List<E>
3458 {
3459 private static final long serialVersionUID = 65247728283967356L;
3460 final List<E> list;
3461
3462 CheckedList(List<E> list, Class<E> type) {
3463 super(list, type);
3464 this.list = list;
3465 }
3466
3467 public boolean equals(Object o) { return o == this || list.equals(o); }
3468 public int hashCode() { return list.hashCode(); }
3469 public E get(int index) { return list.get(index); }
3470 public E remove(int index) { return list.remove(index); }
3471 public int indexOf(Object o) { return list.indexOf(o); }
3472 public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
3473
3474 public E set(int index, E element) {
3475 typeCheck(element);
3476 return list.set(index, element);
3477 }
3478
3479 public void add(int index, E element) {
3480 typeCheck(element);
3481 list.add(index, element);
3482 }
3483
3484 public boolean addAll(int index, Collection<? extends E> c) {
3485 return list.addAll(index, checkedCopyOf(c));
3486 }
3487 public ListIterator<E> listIterator() { return listIterator(0); }
3488
3489 public ListIterator<E> listIterator(final int index) {
3490 final ListIterator<E> i = list.listIterator(index);
3491
3492 return new ListIterator<E>() {
3493 public boolean hasNext() { return i.hasNext(); }
3494 public E next() { return i.next(); }
3495 public boolean hasPrevious() { return i.hasPrevious(); }
3496 public E previous() { return i.previous(); }
3497 public int nextIndex() { return i.nextIndex(); }
3498 public int previousIndex() { return i.previousIndex(); }
3499 public void remove() { i.remove(); }
3500
3501 public void set(E e) {
3502 typeCheck(e);
3503 i.set(e);
3504 }
3505
3506 public void add(E e) {
3507 typeCheck(e);
3508 i.add(e);
3509 }
3510
3511 @Override
3512 public void forEachRemaining(Consumer<? super E> action) {
3513 i.forEachRemaining(action);
3514 }
3515 };
3516 }
3517
3518 public List<E> subList(int fromIndex, int toIndex) {
3519 return new CheckedList<>(list.subList(fromIndex, toIndex), type);
3520 }
3521
3522 @Override
3523 public void replaceAll(UnaryOperator<E> operator) {
3524 list.replaceAll(operator);
3525 }
3526 @Override
3527 public void sort(Comparator<? super E> c) {
3528 list.sort(c);
3529 }
3530 }
3531
3532 /**
3533 * @serial include
3534 */
3535 static class CheckedRandomAccessList<E> extends CheckedList<E>
3536 implements RandomAccess
3537 {
3538 private static final long serialVersionUID = 1638200125423088369L;
3539
3540 CheckedRandomAccessList(List<E> list, Class<E> type) {
3541 super(list, type);
3542 }
3543
3544 public List<E> subList(int fromIndex, int toIndex) {
3545 return new CheckedRandomAccessList<>(
3546 list.subList(fromIndex, toIndex), type);
3547 }
3548 }
3549
3550 /**
3551 * Returns a dynamically typesafe view of the specified map.
3552 * Any attempt to insert a mapping whose key or value have the wrong
3553 * type will result in an immediate {@link ClassCastException}.
3554 * Similarly, any attempt to modify the value currently associated with
3555 * a key will result in an immediate {@link ClassCastException},
3556 * whether the modification is attempted directly through the map
3557 * itself, or through a {@link Map.Entry} instance obtained from the
3558 * map's {@link Map#entrySet() entry set} view.
3559 *
3560 * <p>Assuming a map contains no incorrectly typed keys or values
3561 * prior to the time a dynamically typesafe view is generated, and
3562 * that all subsequent access to the map takes place through the view
3563 * (or one of its collection views), it is <i>guaranteed</i> that the
3564 * map cannot contain an incorrectly typed key or value.
3565 *
3566 * <p>A discussion of the use of dynamically typesafe views may be
3567 * found in the documentation for the {@link #checkedCollection
3568 * checkedCollection} method.
3569 *
3570 * <p>The returned map will be serializable if the specified map is
3571 * serializable.
3572 *
3573 * <p>Since {@code null} is considered to be a value of any reference
3574 * type, the returned map permits insertion of null keys or values
3575 * whenever the backing map does.
3576 *
3577 * @param <K> the class of the map keys
3578 * @param <V> the class of the map values
3579 * @param m the map for which a dynamically typesafe view is to be
3580 * returned
3581 * @param keyType the type of key that {@code m} is permitted to hold
3582 * @param valueType the type of value that {@code m} is permitted to hold
3583 * @return a dynamically typesafe view of the specified map
3584 * @since 1.5
3585 */
3586 public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
3587 Class<K> keyType,
3588 Class<V> valueType) {
3589 return new CheckedMap<>(m, keyType, valueType);
3590 }
3591
3592
3593 /**
3594 * @serial include
3595 */
3596 private static class CheckedMap<K,V>
3597 implements Map<K,V>, Serializable
3598 {
3599 private static final long serialVersionUID = 5742860141034234728L;
3600
3601 private final Map<K, V> m;
3602 final Class<K> keyType;
3603 final Class<V> valueType;
3604
3605 private void typeCheck(Object key, Object value) {
3606 if (key != null && !keyType.isInstance(key))
3607 throw new ClassCastException(badKeyMsg(key));
3608
3609 if (value != null && !valueType.isInstance(value))
3610 throw new ClassCastException(badValueMsg(value));
3611 }
3612
3613 private BiFunction<? super K, ? super V, ? extends V> typeCheck(
3614 BiFunction<? super K, ? super V, ? extends V> func) {
3615 Objects.requireNonNull(func);
3616 return (k, v) -> {
3617 V newValue = func.apply(k, v);
3618 typeCheck(k, newValue);
3619 return newValue;
3620 };
3621 }
3622
3623 private String badKeyMsg(Object key) {
3624 return "Attempt to insert " + key.getClass() +
3625 " key into map with key type " + keyType;
3626 }
3627
3628 private String badValueMsg(Object value) {
3629 return "Attempt to insert " + value.getClass() +
3630 " value into map with value type " + valueType;
3631 }
3632
3633 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
3634 this.m = Objects.requireNonNull(m);
3635 this.keyType = Objects.requireNonNull(keyType);
3636 this.valueType = Objects.requireNonNull(valueType);
3637 }
3638
3639 public int size() { return m.size(); }
3640 public boolean isEmpty() { return m.isEmpty(); }
3641 public boolean containsKey(Object key) { return m.containsKey(key); }
3642 public boolean containsValue(Object v) { return m.containsValue(v); }
3643 public V get(Object key) { return m.get(key); }
3644 public V remove(Object key) { return m.remove(key); }
3645 public void clear() { m.clear(); }
3646 public Set<K> keySet() { return m.keySet(); }
3647 public Collection<V> values() { return m.values(); }
3648 public boolean equals(Object o) { return o == this || m.equals(o); }
3649 public int hashCode() { return m.hashCode(); }
3650 public String toString() { return m.toString(); }
3651
3652 public V put(K key, V value) {
3653 typeCheck(key, value);
3654 return m.put(key, value);
3655 }
3656
3657 @SuppressWarnings("unchecked")
3658 public void putAll(Map<? extends K, ? extends V> t) {
3659 // Satisfy the following goals:
3660 // - good diagnostics in case of type mismatch
3661 // - all-or-nothing semantics
3662 // - protection from malicious t
3663 // - correct behavior if t is a concurrent map
3664 Object[] entries = t.entrySet().toArray();
3665 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length);
3666 for (Object o : entries) {
3667 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3668 Object k = e.getKey();
3669 Object v = e.getValue();
3670 typeCheck(k, v);
3671 checked.add(
3672 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v));
3673 }
3674 for (Map.Entry<K,V> e : checked)
3675 m.put(e.getKey(), e.getValue());
3676 }
3677
3678 private transient Set<Map.Entry<K,V>> entrySet = null;
3679
3680 public Set<Map.Entry<K,V>> entrySet() {
3681 if (entrySet==null)
3682 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
3683 return entrySet;
3684 }
3685
3686 // Override default methods in Map
3687 @Override
3688 public void forEach(BiConsumer<? super K, ? super V> action) {
3689 m.forEach(action);
3690 }
3691
3692 @Override
3693 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
3694 m.replaceAll(typeCheck(function));
3695 }
3696
3697 @Override
3698 public V putIfAbsent(K key, V value) {
3699 typeCheck(key, value);
3700 return m.putIfAbsent(key, value);
3701 }
3702
3703 @Override
3704 public boolean remove(Object key, Object value) {
3705 return m.remove(key, value);
3706 }
3707
3708 @Override
3709 public boolean replace(K key, V oldValue, V newValue) {
3710 typeCheck(key, newValue);
3711 return m.replace(key, oldValue, newValue);
3712 }
3713
3714 @Override
3715 public V replace(K key, V value) {
3716 typeCheck(key, value);
3717 return m.replace(key, value);
3718 }
3719
3720 @Override
3721 public V computeIfAbsent(K key,
3722 Function<? super K, ? extends V> mappingFunction) {
3723 Objects.requireNonNull(mappingFunction);
3724 return m.computeIfAbsent(key, k -> {
3725 V value = mappingFunction.apply(k);
3726 typeCheck(k, value);
3727 return value;
3728 });
3729 }
3730
3731 @Override
3732 public V computeIfPresent(K key,
3733 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3734 return m.computeIfPresent(key, typeCheck(remappingFunction));
3735 }
3736
3737 @Override
3738 public V compute(K key,
3739 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3740 return m.compute(key, typeCheck(remappingFunction));
3741 }
3742
3743 @Override
3744 public V merge(K key, V value,
3745 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
3746 Objects.requireNonNull(remappingFunction);
3747 return m.merge(key, value, (v1, v2) -> {
3748 V newValue = remappingFunction.apply(v1, v2);
3749 typeCheck(null, newValue);
3750 return newValue;
3751 });
3752 }
3753
3754 /**
3755 * We need this class in addition to CheckedSet as Map.Entry permits
3756 * modification of the backing Map via the setValue operation. This
3757 * class is subtle: there are many possible attacks that must be
3758 * thwarted.
3759 *
3760 * @serial exclude
3761 */
3762 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
3763 private final Set<Map.Entry<K,V>> s;
3764 private final Class<V> valueType;
3765
3766 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
3767 this.s = s;
3768 this.valueType = valueType;
3769 }
3770
3771 public int size() { return s.size(); }
3772 public boolean isEmpty() { return s.isEmpty(); }
3773 public String toString() { return s.toString(); }
3774 public int hashCode() { return s.hashCode(); }
3775 public void clear() { s.clear(); }
3776
3777 public boolean add(Map.Entry<K, V> e) {
3778 throw new UnsupportedOperationException();
3779 }
3780 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
3781 throw new UnsupportedOperationException();
3782 }
3783
3784 public Iterator<Map.Entry<K,V>> iterator() {
3785 final Iterator<Map.Entry<K, V>> i = s.iterator();
3786 final Class<V> valueType = this.valueType;
3787
3788 return new Iterator<Map.Entry<K,V>>() {
3789 public boolean hasNext() { return i.hasNext(); }
3790 public void remove() { i.remove(); }
3791
3792 public Map.Entry<K,V> next() {
3793 return checkedEntry(i.next(), valueType);
3794 }
3795 };
3796 }
3797
3798 @SuppressWarnings("unchecked")
3799 public Object[] toArray() {
3800 Object[] source = s.toArray();
3801
3802 /*
3803 * Ensure that we don't get an ArrayStoreException even if
3804 * s.toArray returns an array of something other than Object
3805 */
3806 Object[] dest = (CheckedEntry.class.isInstance(
3807 source.getClass().getComponentType()) ? source :
3808 new Object[source.length]);
3809
3810 for (int i = 0; i < source.length; i++)
3811 dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
3812 valueType);
3813 return dest;
3814 }
3815
3816 @SuppressWarnings("unchecked")
3817 public <T> T[] toArray(T[] a) {
3818 // We don't pass a to s.toArray, to avoid window of
3819 // vulnerability wherein an unscrupulous multithreaded client
3820 // could get his hands on raw (unwrapped) Entries from s.
3821 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
3822
3823 for (int i=0; i<arr.length; i++)
3824 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
3825 valueType);
3826 if (arr.length > a.length)
3827 return arr;
3828
3829 System.arraycopy(arr, 0, a, 0, arr.length);
3830 if (a.length > arr.length)
3831 a[arr.length] = null;
3832 return a;
3833 }
3834
3835 /**
3836 * This method is overridden to protect the backing set against
3837 * an object with a nefarious equals function that senses
3838 * that the equality-candidate is Map.Entry and calls its
3839 * setValue method.
3840 */
3841 public boolean contains(Object o) {
3842 if (!(o instanceof Map.Entry))
3843 return false;
3844 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3845 return s.contains(
3846 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
3847 }
3848
3849 /**
3850 * The bulk collection methods are overridden to protect
3851 * against an unscrupulous collection whose contains(Object o)
3852 * method senses when o is a Map.Entry, and calls o.setValue.
3853 */
3854 public boolean containsAll(Collection<?> c) {
3855 for (Object o : c)
3856 if (!contains(o)) // Invokes safe contains() above
3857 return false;
3858 return true;
3859 }
3860
3861 public boolean remove(Object o) {
3862 if (!(o instanceof Map.Entry))
3863 return false;
3864 return s.remove(new AbstractMap.SimpleImmutableEntry
3865 <>((Map.Entry<?,?>)o));
3866 }
3867
3868 public boolean removeAll(Collection<?> c) {
3869 return batchRemove(c, false);
3870 }
3871 public boolean retainAll(Collection<?> c) {
3872 return batchRemove(c, true);
3873 }
3874 private boolean batchRemove(Collection<?> c, boolean complement) {
3875 boolean modified = false;
3876 Iterator<Map.Entry<K,V>> it = iterator();
3877 while (it.hasNext()) {
3878 if (c.contains(it.next()) != complement) {
3879 it.remove();
3880 modified = true;
3881 }
3882 }
3883 return modified;
3884 }
3885
3886 public boolean equals(Object o) {
3887 if (o == this)
3888 return true;
3889 if (!(o instanceof Set))
3890 return false;
3891 Set<?> that = (Set<?>) o;
3892 return that.size() == s.size()
3893 && containsAll(that); // Invokes safe containsAll() above
3894 }
3895
3896 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
3897 Class<T> valueType) {
3898 return new CheckedEntry<>(e, valueType);
3899 }
3900
3901 /**
3902 * This "wrapper class" serves two purposes: it prevents
3903 * the client from modifying the backing Map, by short-circuiting
3904 * the setValue method, and it protects the backing Map against
3905 * an ill-behaved Map.Entry that attempts to modify another
3906 * Map.Entry when asked to perform an equality check.
3907 */
3908 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
3909 private final Map.Entry<K, V> e;
3910 private final Class<T> valueType;
3911
3912 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
3913 this.e = Objects.requireNonNull(e);
3914 this.valueType = Objects.requireNonNull(valueType);
3915 }
3916
3917 public K getKey() { return e.getKey(); }
3918 public V getValue() { return e.getValue(); }
3919 public int hashCode() { return e.hashCode(); }
3920 public String toString() { return e.toString(); }
3921
3922 public V setValue(V value) {
3923 if (value != null && !valueType.isInstance(value))
3924 throw new ClassCastException(badValueMsg(value));
3925 return e.setValue(value);
3926 }
3927
3928 private String badValueMsg(Object value) {
3929 return "Attempt to insert " + value.getClass() +
3930 " value into map with value type " + valueType;
3931 }
3932
3933 public boolean equals(Object o) {
3934 if (o == this)
3935 return true;
3936 if (!(o instanceof Map.Entry))
3937 return false;
3938 return e.equals(new AbstractMap.SimpleImmutableEntry
3939 <>((Map.Entry<?,?>)o));
3940 }
3941 }
3942 }
3943 }
3944
3945 /**
3946 * Returns a dynamically typesafe view of the specified sorted map.
3947 * Any attempt to insert a mapping whose key or value have the wrong
3948 * type will result in an immediate {@link ClassCastException}.
3949 * Similarly, any attempt to modify the value currently associated with
3950 * a key will result in an immediate {@link ClassCastException},
3951 * whether the modification is attempted directly through the map
3952 * itself, or through a {@link Map.Entry} instance obtained from the
3953 * map's {@link Map#entrySet() entry set} view.
3954 *
3955 * <p>Assuming a map contains no incorrectly typed keys or values
3956 * prior to the time a dynamically typesafe view is generated, and
3957 * that all subsequent access to the map takes place through the view
3958 * (or one of its collection views), it is <i>guaranteed</i> that the
3959 * map cannot contain an incorrectly typed key or value.
3960 *
3961 * <p>A discussion of the use of dynamically typesafe views may be
3962 * found in the documentation for the {@link #checkedCollection
3963 * checkedCollection} method.
3964 *
3965 * <p>The returned map will be serializable if the specified map is
3966 * serializable.
3967 *
3968 * <p>Since {@code null} is considered to be a value of any reference
3969 * type, the returned map permits insertion of null keys or values
3970 * whenever the backing map does.
3971 *
3972 * @param <K> the class of the map keys
3973 * @param <V> the class of the map values
3974 * @param m the map for which a dynamically typesafe view is to be
3975 * returned
3976 * @param keyType the type of key that {@code m} is permitted to hold
3977 * @param valueType the type of value that {@code m} is permitted to hold
3978 * @return a dynamically typesafe view of the specified map
3979 * @since 1.5
3980 */
3981 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
3982 Class<K> keyType,
3983 Class<V> valueType) {
3984 return new CheckedSortedMap<>(m, keyType, valueType);
3985 }
3986
3987 /**
3988 * @serial include
3989 */
3990 static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
3991 implements SortedMap<K,V>, Serializable
3992 {
3993 private static final long serialVersionUID = 1599671320688067438L;
3994
3995 private final SortedMap<K, V> sm;
3996
3997 CheckedSortedMap(SortedMap<K, V> m,
3998 Class<K> keyType, Class<V> valueType) {
3999 super(m, keyType, valueType);
4000 sm = m;
4001 }
4002
4003 public Comparator<? super K> comparator() { return sm.comparator(); }
4004 public K firstKey() { return sm.firstKey(); }
4005 public K lastKey() { return sm.lastKey(); }
4006
4007 public SortedMap<K,V> subMap(K fromKey, K toKey) {
4008 return checkedSortedMap(sm.subMap(fromKey, toKey),
4009 keyType, valueType);
4010 }
4011 public SortedMap<K,V> headMap(K toKey) {
4012 return checkedSortedMap(sm.headMap(toKey), keyType, valueType);
4013 }
4014 public SortedMap<K,V> tailMap(K fromKey) {
4015 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType);
4016 }
4017 }
4018
4019 /**
4020 * Returns a dynamically typesafe view of the specified navigable map.
4021 * Any attempt to insert a mapping whose key or value have the wrong
4022 * type will result in an immediate {@link ClassCastException}.
4023 * Similarly, any attempt to modify the value currently associated with
4024 * a key will result in an immediate {@link ClassCastException},
4025 * whether the modification is attempted directly through the map
4026 * itself, or through a {@link Map.Entry} instance obtained from the
4027 * map's {@link Map#entrySet() entry set} view.
4028 *
4029 * <p>Assuming a map contains no incorrectly typed keys or values
4030 * prior to the time a dynamically typesafe view is generated, and
4031 * that all subsequent access to the map takes place through the view
4032 * (or one of its collection views), it is <em>guaranteed</em> that the
4033 * map cannot contain an incorrectly typed key or value.
4034 *
4035 * <p>A discussion of the use of dynamically typesafe views may be
4036 * found in the documentation for the {@link #checkedCollection
4037 * checkedCollection} method.
4038 *
4039 * <p>The returned map will be serializable if the specified map is
4040 * serializable.
4041 *
4042 * <p>Since {@code null} is considered to be a value of any reference
4043 * type, the returned map permits insertion of null keys or values
4044 * whenever the backing map does.
4045 *
4046 * @param <K> type of map keys
4047 * @param <V> type of map values
4048 * @param m the map for which a dynamically typesafe view is to be
4049 * returned
4050 * @param keyType the type of key that {@code m} is permitted to hold
4051 * @param valueType the type of value that {@code m} is permitted to hold
4052 * @return a dynamically typesafe view of the specified map
4053 * @since 1.8
4054 */
4055 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m,
4056 Class<K> keyType,
4057 Class<V> valueType) {
4058 return new CheckedNavigableMap<>(m, keyType, valueType);
4059 }
4060
4061 /**
4062 * @serial include
4063 */
4064 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V>
4065 implements NavigableMap<K,V>, Serializable
4066 {
4067 private static final long serialVersionUID = -4852462692372534096L;
4068
4069 private final NavigableMap<K, V> nm;
4070
4071 CheckedNavigableMap(NavigableMap<K, V> m,
4072 Class<K> keyType, Class<V> valueType) {
4073 super(m, keyType, valueType);
4074 nm = m;
4075 }
4076
4077 public Comparator<? super K> comparator() { return nm.comparator(); }
4078 public K firstKey() { return nm.firstKey(); }
4079 public K lastKey() { return nm.lastKey(); }
4080
4081 public Entry<K, V> lowerEntry(K key) {
4082 Entry<K,V> lower = nm.lowerEntry(key);
4083 return (null != lower)
4084 ? new CheckedMap.CheckedEntrySet.CheckedEntry(lower, valueType)
4085 : null;
4086 }
4087
4088 public K lowerKey(K key) { return nm.lowerKey(key); }
4089
4090 public Entry<K, V> floorEntry(K key) {
4091 Entry<K,V> floor = nm.floorEntry(key);
4092 return (null != floor)
4093 ? new CheckedMap.CheckedEntrySet.CheckedEntry(floor, valueType)
4094 : null;
4095 }
4096
4097 public K floorKey(K key) { return nm.floorKey(key); }
4098
4099 public Entry<K, V> ceilingEntry(K key) {
4100 Entry<K,V> ceiling = nm.ceilingEntry(key);
4101 return (null != ceiling)
4102 ? new CheckedMap.CheckedEntrySet.CheckedEntry(ceiling, valueType)
4103 : null;
4104 }
4105
4106 public K ceilingKey(K key) { return nm.ceilingKey(key); }
4107
4108 public Entry<K, V> higherEntry(K key) {
4109 Entry<K,V> higher = nm.higherEntry(key);
4110 return (null != higher)
4111 ? new CheckedMap.CheckedEntrySet.CheckedEntry(higher, valueType)
4112 : null;
4113 }
4114
4115 public K higherKey(K key) { return nm.higherKey(key); }
4116
4117 public Entry<K, V> firstEntry() {
4118 Entry<K,V> first = nm.firstEntry();
4119 return (null != first)
4120 ? new CheckedMap.CheckedEntrySet.CheckedEntry(first, valueType)
4121 : null;
4122 }
4123
4124 public Entry<K, V> lastEntry() {
4125 Entry<K,V> last = nm.lastEntry();
4126 return (null != last)
4127 ? new CheckedMap.CheckedEntrySet.CheckedEntry(last, valueType)
4128 : null;
4129 }
4130
4131 public Entry<K, V> pollFirstEntry() {
4132 Entry<K,V> entry = nm.pollFirstEntry();
4133 return (null == entry)
4134 ? null
4135 : new CheckedMap.CheckedEntrySet.CheckedEntry(entry, valueType);
4136 }
4137
4138 public Entry<K, V> pollLastEntry() {
4139 Entry<K,V> entry = nm.pollLastEntry();
4140 return (null == entry)
4141 ? null
4142 : new CheckedMap.CheckedEntrySet.CheckedEntry(entry, valueType);
4143 }
4144
4145 public NavigableMap<K, V> descendingMap() {
4146 return checkedNavigableMap(nm.descendingMap(), keyType, valueType);
4147 }
4148
4149 public NavigableSet<K> keySet() {
4150 return navigableKeySet();
4151 }
4152
4153 public NavigableSet<K> navigableKeySet() {
4154 return checkedNavigableSet(nm.navigableKeySet(), keyType);
4155 }
4156
4157 public NavigableSet<K> descendingKeySet() {
4158 return checkedNavigableSet(nm.descendingKeySet(), keyType);
4159 }
4160
4161 @Override
4162 public NavigableMap<K,V> subMap(K fromKey, K toKey) {
4163 return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false),
4164 keyType, valueType);
4165 }
4166
4167 @Override
4168 public NavigableMap<K,V> headMap(K toKey) {
4169 return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType);
4170 }
4171
4172 @Override
4173 public NavigableMap<K,V> tailMap(K fromKey) {
4174 return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType);
4175 }
4176
4177 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
4178 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType);
4179 }
4180
4181 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
4182 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType);
4183 }
4184
4185 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
4186 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType);
4187 }
4188 }
4189
4190 // Empty collections
4191
4192 /**
4193 * Returns an iterator that has no elements. More precisely,
4194 *
4195 * <ul>
4196 * <li>{@link Iterator#hasNext hasNext} always returns {@code
4197 * false}.</li>
4198 * <li>{@link Iterator#next next} always throws {@link
4199 * NoSuchElementException}.</li>
4200 * <li>{@link Iterator#remove remove} always throws {@link
4201 * IllegalStateException}.</li>
4202 * </ul>
4203 *
4204 * <p>Implementations of this method are permitted, but not
4205 * required, to return the same object from multiple invocations.
4206 *
4207 * @param <T> type of elements, if there were any, in the iterator
4208 * @return an empty iterator
4209 * @since 1.7
4210 */
4211 @SuppressWarnings("unchecked")
4212 public static <T> Iterator<T> emptyIterator() {
4213 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
4214 }
4215
4216 private static class EmptyIterator<E> implements Iterator<E> {
4217 static final EmptyIterator<Object> EMPTY_ITERATOR
4218 = new EmptyIterator<>();
4219
4220 public boolean hasNext() { return false; }
4221 public E next() { throw new NoSuchElementException(); }
4222 public void remove() { throw new IllegalStateException(); }
4223 @Override
4224 public void forEachRemaining(Consumer<? super E> action) {
4225 Objects.requireNonNull(action);
4226 }
4227 }
4228
4229 /**
4230 * Returns a list iterator that has no elements. More precisely,
4231 *
4232 * <ul>
4233 * <li>{@link Iterator#hasNext hasNext} and {@link
4234 * ListIterator#hasPrevious hasPrevious} always return {@code
4235 * false}.</li>
4236 * <li>{@link Iterator#next next} and {@link ListIterator#previous
4237 * previous} always throw {@link NoSuchElementException}.</li>
4238 * <li>{@link Iterator#remove remove} and {@link ListIterator#set
4239 * set} always throw {@link IllegalStateException}.</li>
4240 * <li>{@link ListIterator#add add} always throws {@link
4241 * UnsupportedOperationException}.</li>
4242 * <li>{@link ListIterator#nextIndex nextIndex} always returns
4243 * {@code 0}.</li>
4244 * <li>{@link ListIterator#previousIndex previousIndex} always
4245 * returns {@code -1}.</li>
4246 * </ul>
4247 *
4248 * <p>Implementations of this method are permitted, but not
4249 * required, to return the same object from multiple invocations.
4250 *
4251 * @param <T> type of elements, if there were any, in the iterator
4252 * @return an empty list iterator
4253 * @since 1.7
4254 */
4255 @SuppressWarnings("unchecked")
4256 public static <T> ListIterator<T> emptyListIterator() {
4257 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
4258 }
4259
4260 private static class EmptyListIterator<E>
4261 extends EmptyIterator<E>
4262 implements ListIterator<E>
4263 {
4264 static final EmptyListIterator<Object> EMPTY_ITERATOR
4265 = new EmptyListIterator<>();
4266
4267 public boolean hasPrevious() { return false; }
4268 public E previous() { throw new NoSuchElementException(); }
4269 public int nextIndex() { return 0; }
4270 public int previousIndex() { return -1; }
4271 public void set(E e) { throw new IllegalStateException(); }
4272 public void add(E e) { throw new UnsupportedOperationException(); }
4273 }
4274
4275 /**
4276 * Returns an enumeration that has no elements. More precisely,
4277 *
4278 * <ul>
4279 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
4280 * returns {@code false}.</li>
4281 * <li> {@link Enumeration#nextElement nextElement} always throws
4282 * {@link NoSuchElementException}.</li>
4283 * </ul>
4284 *
4285 * <p>Implementations of this method are permitted, but not
4286 * required, to return the same object from multiple invocations.
4287 *
4288 * @param <T> the class of the objects in the enumeration
4289 * @return an empty enumeration
4290 * @since 1.7
4291 */
4292 @SuppressWarnings("unchecked")
4293 public static <T> Enumeration<T> emptyEnumeration() {
4294 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
4295 }
4296
4297 private static class EmptyEnumeration<E> implements Enumeration<E> {
4298 static final EmptyEnumeration<Object> EMPTY_ENUMERATION
4299 = new EmptyEnumeration<>();
4300
4301 public boolean hasMoreElements() { return false; }
4302 public E nextElement() { throw new NoSuchElementException(); }
4303 }
4304
4305 /**
4306 * The empty set (immutable). This set is serializable.
4307 *
4308 * @see #emptySet()
4309 */
4310 @SuppressWarnings("rawtypes")
4311 public static final Set EMPTY_SET = new EmptySet<>();
4312
4313 /**
4314 * Returns an empty set (immutable). This set is serializable.
4315 * Unlike the like-named field, this method is parameterized.
4316 *
4317 * <p>This example illustrates the type-safe way to obtain an empty set:
4318 * <pre>
4319 * Set<String> s = Collections.emptySet();
4320 * </pre>
4321 * @implNote Implementations of this method need not create a separate
4322 * {@code Set} object for each call. Using this method is likely to have
4323 * comparable cost to using the like-named field. (Unlike this method, the
4324 * field does not provide type safety.)
4325 *
4326 * @param <T> the class of the objects in the set
4327 * @return the empty set
4328 *
4329 * @see #EMPTY_SET
4330 * @since 1.5
4331 */
4332 @SuppressWarnings("unchecked")
4333 public static final <T> Set<T> emptySet() {
4334 return (Set<T>) EMPTY_SET;
4335 }
4336
4337 /**
4338 * @serial include
4339 */
4340 private static class EmptySet<E>
4341 extends AbstractSet<E>
4342 implements Serializable
4343 {
4344 private static final long serialVersionUID = 1582296315990362920L;
4345
4346 public Iterator<E> iterator() { return emptyIterator(); }
4347
4348 public int size() {return 0;}
4349 public boolean isEmpty() {return true;}
4350
4351 public boolean contains(Object obj) {return false;}
4352 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4353
4354 public Object[] toArray() { return new Object[0]; }
4355
4356 public <T> T[] toArray(T[] a) {
4357 if (a.length > 0)
4358 a[0] = null;
4359 return a;
4360 }
4361
4362 // Override default methods in Collection
4363 @Override
4364 public void forEach(Consumer<? super E> action) {
4365 Objects.requireNonNull(action);
4366 }
4367 @Override
4368 public boolean removeIf(Predicate<? super E> filter) {
4369 Objects.requireNonNull(filter);
4370 return false;
4371 }
4372 @Override
4373 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4374
4375 // Preserves singleton property
4376 private Object readResolve() {
4377 return EMPTY_SET;
4378 }
4379 }
4380
4381 /**
4382 * Returns an empty sorted set (immutable). This set is serializable.
4383 *
4384 * <p>This example illustrates the type-safe way to obtain an empty
4385 * sorted set:
4386 * <pre> {@code
4387 * SortedSet<String> s = Collections.emptySortedSet();
4388 * }</pre>
4389 *
4390 * @implNote Implementations of this method need not create a separate
4391 * {@code SortedSet} object for each call.
4392 *
4393 * @param <E> type of elements, if there were any, in the set
4394 * @return the empty sorted set
4395 * @since 1.8
4396 */
4397 @SuppressWarnings("unchecked")
4398 public static <E> SortedSet<E> emptySortedSet() {
4399 return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
4400 }
4401
4402 /**
4403 * Returns an empty navigable set (immutable). This set is serializable.
4404 *
4405 * <p>This example illustrates the type-safe way to obtain an empty
4406 * navigable set:
4407 * <pre> {@code
4408 * NavigableSet<String> s = Collections.emptyNavigableSet();
4409 * }</pre>
4410 *
4411 * @implNote Implementations of this method need not
4412 * create a separate {@code NavigableSet} object for each call.
4413 *
4414 * @param <E> type of elements, if there were any, in the set
4415 * @return the empty navigable set
4416 * @since 1.8
4417 */
4418 @SuppressWarnings("unchecked")
4419 public static <E> NavigableSet<E> emptyNavigableSet() {
4420 return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
4421 }
4422
4423 /**
4424 * The empty list (immutable). This list is serializable.
4425 *
4426 * @see #emptyList()
4427 */
4428 @SuppressWarnings("rawtypes")
4429 public static final List EMPTY_LIST = new EmptyList<>();
4430
4431 /**
4432 * Returns an empty list (immutable). This list is serializable.
4433 *
4434 * <p>This example illustrates the type-safe way to obtain an empty list:
4435 * <pre>
4436 * List<String> s = Collections.emptyList();
4437 * </pre>
4438 * Implementation note: Implementations of this method need not
4439 * create a separate <tt>List</tt> object for each call. Using this
4440 * method is likely to have comparable cost to using the like-named
4441 * field. (Unlike this method, the field does not provide type safety.)
4442 *
4443 * @param <T> type of elements, if there were any, in the list
4444 * @return an empty immutable list
4445 *
4446 * @see #EMPTY_LIST
4447 * @since 1.5
4448 */
4449 @SuppressWarnings("unchecked")
4450 public static final <T> List<T> emptyList() {
4451 return (List<T>) EMPTY_LIST;
4452 }
4453
4454 /**
4455 * @serial include
4456 */
4457 private static class EmptyList<E>
4458 extends AbstractList<E>
4459 implements RandomAccess, Serializable {
4460 private static final long serialVersionUID = 8842843931221139166L;
4461
4462 public Iterator<E> iterator() {
4463 return emptyIterator();
4464 }
4465 public ListIterator<E> listIterator() {
4466 return emptyListIterator();
4467 }
4468
4469 public int size() {return 0;}
4470 public boolean isEmpty() {return true;}
4471
4472 public boolean contains(Object obj) {return false;}
4473 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4474
4475 public Object[] toArray() { return new Object[0]; }
4476
4477 public <T> T[] toArray(T[] a) {
4478 if (a.length > 0)
4479 a[0] = null;
4480 return a;
4481 }
4482
4483 public E get(int index) {
4484 throw new IndexOutOfBoundsException("Index: "+index);
4485 }
4486
4487 public boolean equals(Object o) {
4488 return (o instanceof List) && ((List<?>)o).isEmpty();
4489 }
4490
4491 public int hashCode() { return 1; }
4492
4493 @Override
4494 public boolean removeIf(Predicate<? super E> filter) {
4495 Objects.requireNonNull(filter);
4496 return false;
4497 }
4498 @Override
4499 public void replaceAll(UnaryOperator<E> operator) {
4500 Objects.requireNonNull(operator);
4501 }
4502 @Override
4503 public void sort(Comparator<? super E> c) {
4504 Objects.requireNonNull(c);
4505 }
4506
4507 // Override default methods in Collection
4508 @Override
4509 public void forEach(Consumer<? super E> action) {
4510 Objects.requireNonNull(action);
4511 }
4512
4513 @Override
4514 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4515
4516 // Preserves singleton property
4517 private Object readResolve() {
4518 return EMPTY_LIST;
4519 }
4520 }
4521
4522 /**
4523 * The empty map (immutable). This map is serializable.
4524 *
4525 * @see #emptyMap()
4526 * @since 1.3
4527 */
4528 @SuppressWarnings("rawtypes")
4529 public static final Map EMPTY_MAP = new EmptyMap<>();
4530
4531 /**
4532 * Returns an empty map (immutable). This map is serializable.
4533 *
4534 * <p>This example illustrates the type-safe way to obtain an empty map:
4535 * <pre>
4536 * Map<String, Date> s = Collections.emptyMap();
4537 * </pre>
4538 * @implNote Implementations of this method need not create a separate
4539 * {@code Map} object for each call. Using this method is likely to have
4540 * comparable cost to using the like-named field. (Unlike this method, the
4541 * field does not provide type safety.)
4542 *
4543 * @param <K> the class of the map keys
4544 * @param <V> the class of the map values
4545 * @return an empty map
4546 * @see #EMPTY_MAP
4547 * @since 1.5
4548 */
4549 @SuppressWarnings("unchecked")
4550 public static final <K,V> Map<K,V> emptyMap() {
4551 return (Map<K,V>) EMPTY_MAP;
4552 }
4553
4554 /**
4555 * Returns an empty sorted map (immutable). This map is serializable.
4556 *
4557 * <p>This example illustrates the type-safe way to obtain an empty map:
4558 * <pre> {@code
4559 * SortedMap<String, Date> s = Collections.emptySortedMap();
4560 * }</pre>
4561 *
4562 * @implNote Implementations of this method need not create a separate
4563 * {@code SortedMap} object for each call.
4564 *
4565 * @param <K> the class of the map keys
4566 * @param <V> the class of the map values
4567 * @return an empty sorted map
4568 * @since 1.8
4569 */
4570 @SuppressWarnings("unchecked")
4571 public static final <K,V> SortedMap<K,V> emptySortedMap() {
4572 return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
4573 }
4574
4575 /**
4576 * Returns an empty navigable map (immutable). This map is serializable.
4577 *
4578 * <p>This example illustrates the type-safe way to obtain an empty map:
4579 * <pre> {@code
4580 * NavigableMap<String, Date> s = Collections.emptyNavigableMap();
4581 * }</pre>
4582 *
4583 * @implNote Implementations of this method need not create a separate
4584 * {@code NavigableMap} object for each call.
4585 *
4586 * @param <K> the class of the map keys
4587 * @param <V> the class of the map values
4588 * @return an empty navigable map
4589 * @since 1.8
4590 */
4591 @SuppressWarnings("unchecked")
4592 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() {
4593 return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
4594 }
4595
4596 /**
4597 * @serial include
4598 */
4599 private static class EmptyMap<K,V>
4600 extends AbstractMap<K,V>
4601 implements Serializable
4602 {
4603 private static final long serialVersionUID = 6428348081105594320L;
4604
4605 public int size() {return 0;}
4606 public boolean isEmpty() {return true;}
4607 public boolean containsKey(Object key) {return false;}
4608 public boolean containsValue(Object value) {return false;}
4609 public V get(Object key) {return null;}
4610 public Set<K> keySet() {return emptySet();}
4611 public Collection<V> values() {return emptySet();}
4612 public Set<Map.Entry<K,V>> entrySet() {return emptySet();}
4613
4614 public boolean equals(Object o) {
4615 return (o instanceof Map) && ((Map<?,?>)o).isEmpty();
4616 }
4617
4618 public int hashCode() {return 0;}
4619
4620 // Override default methods in Map
4621 @Override
4622 @SuppressWarnings("unchecked")
4623 public V getOrDefault(Object k, V defaultValue) {
4624 return defaultValue;
4625 }
4626
4627 @Override
4628 public void forEach(BiConsumer<? super K, ? super V> action) {
4629 Objects.requireNonNull(action);
4630 }
4631
4632 @Override
4633 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4634 Objects.requireNonNull(function);
4635 }
4636
4637 @Override
4638 public V putIfAbsent(K key, V value) {
4639 throw new UnsupportedOperationException();
4640 }
4641
4642 @Override
4643 public boolean remove(Object key, Object value) {
4644 throw new UnsupportedOperationException();
4645 }
4646
4647 @Override
4648 public boolean replace(K key, V oldValue, V newValue) {
4649 throw new UnsupportedOperationException();
4650 }
4651
4652 @Override
4653 public V replace(K key, V value) {
4654 throw new UnsupportedOperationException();
4655 }
4656
4657 @Override
4658 public V computeIfAbsent(K key,
4659 Function<? super K, ? extends V> mappingFunction) {
4660 throw new UnsupportedOperationException();
4661 }
4662
4663 @Override
4664 public V computeIfPresent(K key,
4665 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4666 throw new UnsupportedOperationException();
4667 }
4668
4669 @Override
4670 public V compute(K key,
4671 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4672 throw new UnsupportedOperationException();
4673 }
4674
4675 @Override
4676 public V merge(K key, V value,
4677 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4678 throw new UnsupportedOperationException();
4679 }
4680
4681 // Preserves singleton property
4682 private Object readResolve() {
4683 return EMPTY_MAP;
4684 }
4685 }
4686
4687 // Singleton collections
4688
4689 /**
4690 * Returns an immutable set containing only the specified object.
4691 * The returned set is serializable.
4692 *
4693 * @param <T> the class of the objects in the set
4694 * @param o the sole object to be stored in the returned set.
4695 * @return an immutable set containing only the specified object.
4696 */
4697 public static <T> Set<T> singleton(T o) {
4698 return new SingletonSet<>(o);
4699 }
4700
4701 static <E> Iterator<E> singletonIterator(final E e) {
4702 return new Iterator<E>() {
4703 private boolean hasNext = true;
4704 public boolean hasNext() {
4705 return hasNext;
4706 }
4707 public E next() {
4708 if (hasNext) {
4709 hasNext = false;
4710 return e;
4711 }
4712 throw new NoSuchElementException();
4713 }
4714 public void remove() {
4715 throw new UnsupportedOperationException();
4716 }
4717 @Override
4718 public void forEachRemaining(Consumer<? super E> action) {
4719 Objects.requireNonNull(action);
4720 if (hasNext) {
4721 action.accept(e);
4722 hasNext = false;
4723 }
4724 }
4725 };
4726 }
4727
4728 /**
4729 * Creates a {@code Spliterator} with only the specified element
4730 *
4731 * @param <T> Type of elements
4732 * @return A singleton {@code Spliterator}
4733 */
4734 static <T> Spliterator<T> singletonSpliterator(final T element) {
4735 return new Spliterator<T>() {
4736 long est = 1;
4737
4738 @Override
4739 public Spliterator<T> trySplit() {
4740 return null;
4741 }
4742
4743 @Override
4744 public boolean tryAdvance(Consumer<? super T> consumer) {
4745 Objects.requireNonNull(consumer);
4746 if (est > 0) {
4747 est--;
4748 consumer.accept(element);
4749 return true;
4750 }
4751 return false;
4752 }
4753
4754 @Override
4755 public void forEachRemaining(Consumer<? super T> consumer) {
4756 tryAdvance(consumer);
4757 }
4758
4759 @Override
4760 public long estimateSize() {
4761 return est;
4762 }
4763
4764 @Override
4765 public int characteristics() {
4766 int value = (element != null) ? Spliterator.NONNULL : 0;
4767
4768 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE |
4769 Spliterator.DISTINCT | Spliterator.ORDERED;
4770 }
4771 };
4772 }
4773
4774 /**
4775 * @serial include
4776 */
4777 private static class SingletonSet<E>
4778 extends AbstractSet<E>
4779 implements Serializable
4780 {
4781 private static final long serialVersionUID = 3193687207550431679L;
4782
4783 private final E element;
4784
4785 SingletonSet(E e) {element = e;}
4786
4787 public Iterator<E> iterator() {
4788 return singletonIterator(element);
4789 }
4790
4791 public int size() {return 1;}
4792
4793 public boolean contains(Object o) {return eq(o, element);}
4794
4795 // Override default methods for Collection
4796 @Override
4797 public void forEach(Consumer<? super E> action) {
4798 action.accept(element);
4799 }
4800 @Override
4801 public Spliterator<E> spliterator() {
4802 return singletonSpliterator(element);
4803 }
4804 @Override
4805 public boolean removeIf(Predicate<? super E> filter) {
4806 throw new UnsupportedOperationException();
4807 }
4808 }
4809
4810 /**
4811 * Returns an immutable list containing only the specified object.
4812 * The returned list is serializable.
4813 *
4814 * @param <T> the class of the objects in the list
4815 * @param o the sole object to be stored in the returned list.
4816 * @return an immutable list containing only the specified object.
4817 * @since 1.3
4818 */
4819 public static <T> List<T> singletonList(T o) {
4820 return new SingletonList<>(o);
4821 }
4822
4823 /**
4824 * @serial include
4825 */
4826 private static class SingletonList<E>
4827 extends AbstractList<E>
4828 implements RandomAccess, Serializable {
4829
4830 private static final long serialVersionUID = 3093736618740652951L;
4831
4832 private final E element;
4833
4834 SingletonList(E obj) {element = obj;}
4835
4836 public Iterator<E> iterator() {
4837 return singletonIterator(element);
4838 }
4839
4840 public int size() {return 1;}
4841
4842 public boolean contains(Object obj) {return eq(obj, element);}
4843
4844 public E get(int index) {
4845 if (index != 0)
4846 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
4847 return element;
4848 }
4849
4850 // Override default methods for Collection
4851 @Override
4852 public void forEach(Consumer<? super E> action) {
4853 action.accept(element);
4854 }
4855 @Override
4856 public boolean removeIf(Predicate<? super E> filter) {
4857 throw new UnsupportedOperationException();
4858 }
4859 @Override
4860 public void replaceAll(UnaryOperator<E> operator) {
4861 throw new UnsupportedOperationException();
4862 }
4863 @Override
4864 public void sort(Comparator<? super E> c) {
4865 }
4866 @Override
4867 public Spliterator<E> spliterator() {
4868 return singletonSpliterator(element);
4869 }
4870 }
4871
4872 /**
4873 * Returns an immutable map, mapping only the specified key to the
4874 * specified value. The returned map is serializable.
4875 *
4876 * @param <K> the class of the map keys
4877 * @param <V> the class of the map values
4878 * @param key the sole key to be stored in the returned map.
4879 * @param value the value to which the returned map maps <tt>key</tt>.
4880 * @return an immutable map containing only the specified key-value
4881 * mapping.
4882 * @since 1.3
4883 */
4884 public static <K,V> Map<K,V> singletonMap(K key, V value) {
4885 return new SingletonMap<>(key, value);
4886 }
4887
4888 /**
4889 * @serial include
4890 */
4891 private static class SingletonMap<K,V>
4892 extends AbstractMap<K,V>
4893 implements Serializable {
4894 private static final long serialVersionUID = -6979724477215052911L;
4895
4896 private final K k;
4897 private final V v;
4898
4899 SingletonMap(K key, V value) {
4900 k = key;
4901 v = value;
4902 }
4903
4904 public int size() {return 1;}
4905 public boolean isEmpty() {return false;}
4906 public boolean containsKey(Object key) {return eq(key, k);}
4907 public boolean containsValue(Object value) {return eq(value, v);}
4908 public V get(Object key) {return (eq(key, k) ? v : null);}
4909
4910 private transient Set<K> keySet = null;
4911 private transient Set<Map.Entry<K,V>> entrySet = null;
4912 private transient Collection<V> values = null;
4913
4914 public Set<K> keySet() {
4915 if (keySet==null)
4916 keySet = singleton(k);
4917 return keySet;
4918 }
4919
4920 public Set<Map.Entry<K,V>> entrySet() {
4921 if (entrySet==null)
4922 entrySet = Collections.<Map.Entry<K,V>>singleton(
4923 new SimpleImmutableEntry<>(k, v));
4924 return entrySet;
4925 }
4926
4927 public Collection<V> values() {
4928 if (values==null)
4929 values = singleton(v);
4930 return values;
4931 }
4932
4933 // Override default methods in Map
4934 @Override
4935 public V getOrDefault(Object key, V defaultValue) {
4936 return eq(key, k) ? v : defaultValue;
4937 }
4938
4939 @Override
4940 public void forEach(BiConsumer<? super K, ? super V> action) {
4941 action.accept(k, v);
4942 }
4943
4944 @Override
4945 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4946 throw new UnsupportedOperationException();
4947 }
4948
4949 @Override
4950 public V putIfAbsent(K key, V value) {
4951 throw new UnsupportedOperationException();
4952 }
4953
4954 @Override
4955 public boolean remove(Object key, Object value) {
4956 throw new UnsupportedOperationException();
4957 }
4958
4959 @Override
4960 public boolean replace(K key, V oldValue, V newValue) {
4961 throw new UnsupportedOperationException();
4962 }
4963
4964 @Override
4965 public V replace(K key, V value) {
4966 throw new UnsupportedOperationException();
4967 }
4968
4969 @Override
4970 public V computeIfAbsent(K key,
4971 Function<? super K, ? extends V> mappingFunction) {
4972 throw new UnsupportedOperationException();
4973 }
4974
4975 @Override
4976 public V computeIfPresent(K key,
4977 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4978 throw new UnsupportedOperationException();
4979 }
4980
4981 @Override
4982 public V compute(K key,
4983 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4984 throw new UnsupportedOperationException();
4985 }
4986
4987 @Override
4988 public V merge(K key, V value,
4989 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4990 throw new UnsupportedOperationException();
4991 }
4992 }
4993
4994 // Miscellaneous
4995
4996 /**
4997 * Returns an immutable list consisting of <tt>n</tt> copies of the
4998 * specified object. The newly allocated data object is tiny (it contains
4999 * a single reference to the data object). This method is useful in
5000 * combination with the <tt>List.addAll</tt> method to grow lists.
5001 * The returned list is serializable.
5002 *
5003 * @param <T> the class of the object to copy and of the objects
5004 * in the returned list.
5005 * @param n the number of elements in the returned list.
5006 * @param o the element to appear repeatedly in the returned list.
5007 * @return an immutable list consisting of <tt>n</tt> copies of the
5008 * specified object.
5009 * @throws IllegalArgumentException if {@code n < 0}
5010 * @see List#addAll(Collection)
5011 * @see List#addAll(int, Collection)
5012 */
5013 public static <T> List<T> nCopies(int n, T o) {
5014 if (n < 0)
5015 throw new IllegalArgumentException("List length = " + n);
5016 return new CopiesList<>(n, o);
5017 }
5018
5019 /**
5020 * @serial include
5021 */
5022 private static class CopiesList<E>
5023 extends AbstractList<E>
5024 implements RandomAccess, Serializable
5025 {
5026 private static final long serialVersionUID = 2739099268398711800L;
5027
5028 final int n;
5029 final E element;
5030
5031 CopiesList(int n, E e) {
5032 assert n >= 0;
5033 this.n = n;
5034 element = e;
5035 }
5036
5037 public int size() {
5038 return n;
5039 }
5040
5041 public boolean contains(Object obj) {
5042 return n != 0 && eq(obj, element);
5043 }
5044
5045 public int indexOf(Object o) {
5046 return contains(o) ? 0 : -1;
5047 }
5048
5049 public int lastIndexOf(Object o) {
5050 return contains(o) ? n - 1 : -1;
5051 }
5052
5053 public E get(int index) {
5054 if (index < 0 || index >= n)
5055 throw new IndexOutOfBoundsException("Index: "+index+
5056 ", Size: "+n);
5057 return element;
5058 }
5059
5060 public Object[] toArray() {
5061 final Object[] a = new Object[n];
5062 if (element != null)
5063 Arrays.fill(a, 0, n, element);
5064 return a;
5065 }
5066
5067 @SuppressWarnings("unchecked")
5068 public <T> T[] toArray(T[] a) {
5069 final int n = this.n;
5070 if (a.length < n) {
5071 a = (T[])java.lang.reflect.Array
5072 .newInstance(a.getClass().getComponentType(), n);
5073 if (element != null)
5074 Arrays.fill(a, 0, n, element);
5075 } else {
5076 Arrays.fill(a, 0, n, element);
5077 if (a.length > n)
5078 a[n] = null;
5079 }
5080 return a;
5081 }
5082
5083 public List<E> subList(int fromIndex, int toIndex) {
5084 if (fromIndex < 0)
5085 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
5086 if (toIndex > n)
5087 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
5088 if (fromIndex > toIndex)
5089 throw new IllegalArgumentException("fromIndex(" + fromIndex +
5090 ") > toIndex(" + toIndex + ")");
5091 return new CopiesList<>(toIndex - fromIndex, element);
5092 }
5093 }
5094
5095 /**
5096 * Returns a comparator that imposes the reverse of the <em>natural
5097 * ordering</em> on a collection of objects that implement the
5098 * {@code Comparable} interface. (The natural ordering is the ordering
5099 * imposed by the objects' own {@code compareTo} method.) This enables a
5100 * simple idiom for sorting (or maintaining) collections (or arrays) of
5101 * objects that implement the {@code Comparable} interface in
5102 * reverse-natural-order. For example, suppose {@code a} is an array of
5103 * strings. Then: <pre>
5104 * Arrays.sort(a, Collections.reverseOrder());
5105 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
5106 *
5107 * The returned comparator is serializable.
5108 *
5109 * @param <T> the class of the objects compared by the comparator
5110 * @return A comparator that imposes the reverse of the <i>natural
5111 * ordering</i> on a collection of objects that implement
5112 * the <tt>Comparable</tt> interface.
5113 * @see Comparable
5114 */
5115 @SuppressWarnings("unchecked")
5116 public static <T> Comparator<T> reverseOrder() {
5117 return (Comparator<T>) ReverseComparator.REVERSE_ORDER;
5118 }
5119
5120 /**
5121 * @serial include
5122 */
5123 private static class ReverseComparator
5124 implements Comparator<Comparable<Object>>, Serializable {
5125
5126 private static final long serialVersionUID = 7207038068494060240L;
5127
5128 static final ReverseComparator REVERSE_ORDER
5129 = new ReverseComparator();
5130
5131 public int compare(Comparable<Object> c1, Comparable<Object> c2) {
5132 return c2.compareTo(c1);
5133 }
5134
5135 private Object readResolve() { return Collections.reverseOrder(); }
5136
5137 @Override
5138 public Comparator<Comparable<Object>> reversed() {
5139 return Comparator.naturalOrder();
5140 }
5141 }
5142
5143 /**
5144 * Returns a comparator that imposes the reverse ordering of the specified
5145 * comparator. If the specified comparator is {@code null}, this method is
5146 * equivalent to {@link #reverseOrder()} (in other words, it returns a
5147 * comparator that imposes the reverse of the <em>natural ordering</em> on
5148 * a collection of objects that implement the Comparable interface).
5149 *
5150 * <p>The returned comparator is serializable (assuming the specified
5151 * comparator is also serializable or {@code null}).
5152 *
5153 * @param <T> the class of the objects compared by the comparator
5154 * @param cmp a comparator who's ordering is to be reversed by the returned
5155 * comparator or {@code null}
5156 * @return A comparator that imposes the reverse ordering of the
5157 * specified comparator.
5158 * @since 1.5
5159 */
5160 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
5161 if (cmp == null)
5162 return reverseOrder();
5163
5164 if (cmp instanceof ReverseComparator2)
5165 return ((ReverseComparator2<T>)cmp).cmp;
5166
5167 return new ReverseComparator2<>(cmp);
5168 }
5169
5170 /**
5171 * @serial include
5172 */
5173 private static class ReverseComparator2<T> implements Comparator<T>,
5174 Serializable
5175 {
5176 private static final long serialVersionUID = 4374092139857L;
5177
5178 /**
5179 * The comparator specified in the static factory. This will never
5180 * be null, as the static factory returns a ReverseComparator
5181 * instance if its argument is null.
5182 *
5183 * @serial
5184 */
5185 final Comparator<T> cmp;
5186
5187 ReverseComparator2(Comparator<T> cmp) {
5188 assert cmp != null;
5189 this.cmp = cmp;
5190 }
5191
5192 public int compare(T t1, T t2) {
5193 return cmp.compare(t2, t1);
5194 }
5195
5196 public boolean equals(Object o) {
5197 return (o == this) ||
5198 (o instanceof ReverseComparator2 &&
5199 cmp.equals(((ReverseComparator2)o).cmp));
5200 }
5201
5202 public int hashCode() {
5203 return cmp.hashCode() ^ Integer.MIN_VALUE;
5204 }
5205
5206 @Override
5207 public Comparator<T> reversed() {
5208 return cmp;
5209 }
5210 }
5211
5212 /**
5213 * Returns an enumeration over the specified collection. This provides
5214 * interoperability with legacy APIs that require an enumeration
5215 * as input.
5216 *
5217 * @param <T> the class of the objects in the collection
5218 * @param c the collection for which an enumeration is to be returned.
5219 * @return an enumeration over the specified collection.
5220 * @see Enumeration
5221 */
5222 public static <T> Enumeration<T> enumeration(final Collection<T> c) {
5223 return new Enumeration<T>() {
5224 private final Iterator<T> i = c.iterator();
5225
5226 public boolean hasMoreElements() {
5227 return i.hasNext();
5228 }
5229
5230 public T nextElement() {
5231 return i.next();
5232 }
5233 };
5234 }
5235
5236 /**
5237 * Returns an array list containing the elements returned by the
5238 * specified enumeration in the order they are returned by the
5239 * enumeration. This method provides interoperability between
5240 * legacy APIs that return enumerations and new APIs that require
5241 * collections.
5242 *
5243 * @param <T> the class of the objects returned by the enumeration
5244 * @param e enumeration providing elements for the returned
5245 * array list
5246 * @return an array list containing the elements returned
5247 * by the specified enumeration.
5248 * @since 1.4
5249 * @see Enumeration
5250 * @see ArrayList
5251 */
5252 public static <T> ArrayList<T> list(Enumeration<T> e) {
5253 ArrayList<T> l = new ArrayList<>();
5254 while (e.hasMoreElements())
5255 l.add(e.nextElement());
5256 return l;
5257 }
5258
5259 /**
5260 * Returns true if the specified arguments are equal, or both null.
5261 *
5262 * NB: Do not replace with Object.equals until JDK-8015417 is resolved.
5263 */
5264 static boolean eq(Object o1, Object o2) {
5265 return o1==null ? o2==null : o1.equals(o2);
5266 }
5267
5268 /**
5269 * Returns the number of elements in the specified collection equal to the
5270 * specified object. More formally, returns the number of elements
5271 * <tt>e</tt> in the collection such that
5272 * <tt>(o == null ? e == null : o.equals(e))</tt>.
5273 *
5274 * @param c the collection in which to determine the frequency
5275 * of <tt>o</tt>
5276 * @param o the object whose frequency is to be determined
5277 * @return the number of elements in {@code c} equal to {@code o}
5278 * @throws NullPointerException if <tt>c</tt> is null
5279 * @since 1.5
5280 */
5281 public static int frequency(Collection<?> c, Object o) {
5282 int result = 0;
5283 if (o == null) {
5284 for (Object e : c)
5285 if (e == null)
5286 result++;
5287 } else {
5288 for (Object e : c)
5289 if (o.equals(e))
5290 result++;
5291 }
5292 return result;
5293 }
5294
5295 /**
5296 * Returns {@code true} if the two specified collections have no
5297 * elements in common.
5298 *
5299 * <p>Care must be exercised if this method is used on collections that
5300 * do not comply with the general contract for {@code Collection}.
5301 * Implementations may elect to iterate over either collection and test
5302 * for containment in the other collection (or to perform any equivalent
5303 * computation). If either collection uses a nonstandard equality test
5304 * (as does a {@link SortedSet} whose ordering is not <em>compatible with
5305 * equals</em>, or the key set of an {@link IdentityHashMap}), both
5306 * collections must use the same nonstandard equality test, or the
5307 * result of this method is undefined.
5308 *
5309 * <p>Care must also be exercised when using collections that have
5310 * restrictions on the elements that they may contain. Collection
5311 * implementations are allowed to throw exceptions for any operation
5312 * involving elements they deem ineligible. For absolute safety the
5313 * specified collections should contain only elements which are
5314 * eligible elements for both collections.
5315 *
5316 * <p>Note that it is permissible to pass the same collection in both
5317 * parameters, in which case the method will return {@code true} if and
5318 * only if the collection is empty.
5319 *
5320 * @param c1 a collection
5321 * @param c2 a collection
5322 * @return {@code true} if the two specified collections have no
5323 * elements in common.
5324 * @throws NullPointerException if either collection is {@code null}.
5325 * @throws NullPointerException if one collection contains a {@code null}
5326 * element and {@code null} is not an eligible element for the other collection.
5327 * (<a href="Collection.html#optional-restrictions">optional</a>)
5328 * @throws ClassCastException if one collection contains an element that is
5329 * of a type which is ineligible for the other collection.
5330 * (<a href="Collection.html#optional-restrictions">optional</a>)
5331 * @since 1.5
5332 */
5333 public static boolean disjoint(Collection<?> c1, Collection<?> c2) {
5334 // The collection to be used for contains(). Preference is given to
5335 // the collection who's contains() has lower O() complexity.
5336 Collection<?> contains = c2;
5337 // The collection to be iterated. If the collections' contains() impl
5338 // are of different O() complexity, the collection with slower
5339 // contains() will be used for iteration. For collections who's
5340 // contains() are of the same complexity then best performance is
5341 // achieved by iterating the smaller collection.
5342 Collection<?> iterate = c1;
5343
5344 // Performance optimization cases. The heuristics:
5345 // 1. Generally iterate over c1.
5346 // 2. If c1 is a Set then iterate over c2.
5347 // 3. If either collection is empty then result is always true.
5348 // 4. Iterate over the smaller Collection.
5349 if (c1 instanceof Set) {
5350 // Use c1 for contains as a Set's contains() is expected to perform
5351 // better than O(N/2)
5352 iterate = c2;
5353 contains = c1;
5354 } else if (!(c2 instanceof Set)) {
5355 // Both are mere Collections. Iterate over smaller collection.
5356 // Example: If c1 contains 3 elements and c2 contains 50 elements and
5357 // assuming contains() requires ceiling(N/2) comparisons then
5358 // checking for all c1 elements in c2 would require 75 comparisons
5359 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring
5360 // 100 comparisons (50 * ceiling(3/2)).
5361 int c1size = c1.size();
5362 int c2size = c2.size();
5363 if (c1size == 0 || c2size == 0) {
5364 // At least one collection is empty. Nothing will match.
5365 return true;
5366 }
5367
5368 if (c1size > c2size) {
5369 iterate = c2;
5370 contains = c1;
5371 }
5372 }
5373
5374 for (Object e : iterate) {
5375 if (contains.contains(e)) {
5376 // Found a common element. Collections are not disjoint.
5377 return false;
5378 }
5379 }
5380
5381 // No common elements were found.
5382 return true;
5383 }
5384
5385 /**
5386 * Adds all of the specified elements to the specified collection.
5387 * Elements to be added may be specified individually or as an array.
5388 * The behavior of this convenience method is identical to that of
5389 * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely
5390 * to run significantly faster under most implementations.
5391 *
5392 * <p>When elements are specified individually, this method provides a
5393 * convenient way to add a few elements to an existing collection:
5394 * <pre>
5395 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
5396 * </pre>
5397 *
5398 * @param <T> the class of the elements to add and of the collection
5399 * @param c the collection into which <tt>elements</tt> are to be inserted
5400 * @param elements the elements to insert into <tt>c</tt>
5401 * @return <tt>true</tt> if the collection changed as a result of the call
5402 * @throws UnsupportedOperationException if <tt>c</tt> does not support
5403 * the <tt>add</tt> operation
5404 * @throws NullPointerException if <tt>elements</tt> contains one or more
5405 * null values and <tt>c</tt> does not permit null elements, or
5406 * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt>
5407 * @throws IllegalArgumentException if some property of a value in
5408 * <tt>elements</tt> prevents it from being added to <tt>c</tt>
5409 * @see Collection#addAll(Collection)
5410 * @since 1.5
5411 */
5412 @SafeVarargs
5413 public static <T> boolean addAll(Collection<? super T> c, T... elements) {
5414 boolean result = false;
5415 for (T element : elements)
5416 result |= c.add(element);
5417 return result;
5418 }
5419
5420 /**
5421 * Returns a set backed by the specified map. The resulting set displays
5422 * the same ordering, concurrency, and performance characteristics as the
5423 * backing map. In essence, this factory method provides a {@link Set}
5424 * implementation corresponding to any {@link Map} implementation. There
5425 * is no need to use this method on a {@link Map} implementation that
5426 * already has a corresponding {@link Set} implementation (such as {@link
5427 * HashMap} or {@link TreeMap}).
5428 *
5429 * <p>Each method invocation on the set returned by this method results in
5430 * exactly one method invocation on the backing map or its <tt>keySet</tt>
5431 * view, with one exception. The <tt>addAll</tt> method is implemented
5432 * as a sequence of <tt>put</tt> invocations on the backing map.
5433 *
5434 * <p>The specified map must be empty at the time this method is invoked,
5435 * and should not be accessed directly after this method returns. These
5436 * conditions are ensured if the map is created empty, passed directly
5437 * to this method, and no reference to the map is retained, as illustrated
5438 * in the following code fragment:
5439 * <pre>
5440 * Set<Object> weakHashSet = Collections.newSetFromMap(
5441 * new WeakHashMap<Object, Boolean>());
5442 * </pre>
5443 *
5444 * @param <E> the class of the map keys and of the objects in the
5445 * returned set
5446 * @param map the backing map
5447 * @return the set backed by the map
5448 * @throws IllegalArgumentException if <tt>map</tt> is not empty
5449 * @since 1.6
5450 */
5451 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
5452 return new SetFromMap<>(map);
5453 }
5454
5455 /**
5456 * @serial include
5457 */
5458 private static class SetFromMap<E> extends AbstractSet<E>
5459 implements Set<E>, Serializable
5460 {
5461 private final Map<E, Boolean> m; // The backing map
5462 private transient Set<E> s; // Its keySet
5463
5464 SetFromMap(Map<E, Boolean> map) {
5465 if (!map.isEmpty())
5466 throw new IllegalArgumentException("Map is non-empty");
5467 m = map;
5468 s = map.keySet();
5469 }
5470
5471 public void clear() { m.clear(); }
5472 public int size() { return m.size(); }
5473 public boolean isEmpty() { return m.isEmpty(); }
5474 public boolean contains(Object o) { return m.containsKey(o); }
5475 public boolean remove(Object o) { return m.remove(o) != null; }
5476 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
5477 public Iterator<E> iterator() { return s.iterator(); }
5478 public Object[] toArray() { return s.toArray(); }
5479 public <T> T[] toArray(T[] a) { return s.toArray(a); }
5480 public String toString() { return s.toString(); }
5481 public int hashCode() { return s.hashCode(); }
5482 public boolean equals(Object o) { return o == this || s.equals(o); }
5483 public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
5484 public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
5485 public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
5486 // addAll is the only inherited implementation
5487
5488 // Override default methods in Collection
5489 @Override
5490 public void forEach(Consumer<? super E> action) {
5491 s.forEach(action);
5492 }
5493 @Override
5494 public boolean removeIf(Predicate<? super E> filter) {
5495 return s.removeIf(filter);
5496 }
5497
5498 @Override
5499 public Spliterator<E> spliterator() {return s.spliterator();}
5500
5501 private static final long serialVersionUID = 2454657854757543876L;
5502
5503 private void readObject(java.io.ObjectInputStream stream)
5504 throws IOException, ClassNotFoundException
5505 {
5506 stream.defaultReadObject();
5507 s = m.keySet();
5508 }
5509 }
5510
5511 /**
5512 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
5513 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>,
5514 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This
5515 * view can be useful when you would like to use a method
5516 * requiring a <tt>Queue</tt> but you need Lifo ordering.
5517 *
5518 * <p>Each method invocation on the queue returned by this method
5519 * results in exactly one method invocation on the backing deque, with
5520 * one exception. The {@link Queue#addAll addAll} method is
5521 * implemented as a sequence of {@link Deque#addFirst addFirst}
5522 * invocations on the backing deque.
5523 *
5524 * @param <T> the class of the objects in the deque
5525 * @param deque the deque
5526 * @return the queue
5527 * @since 1.6
5528 */
5529 public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
5530 return new AsLIFOQueue<>(deque);
5531 }
5532
5533 /**
5534 * @serial include
5535 */
5536 static class AsLIFOQueue<E> extends AbstractQueue<E>
5537 implements Queue<E>, Serializable {
5538 private static final long serialVersionUID = 1802017725587941708L;
5539 private final Deque<E> q;
5540 AsLIFOQueue(Deque<E> q) { this.q = q; }
5541 public boolean add(E e) { q.addFirst(e); return true; }
5542 public boolean offer(E e) { return q.offerFirst(e); }
5543 public E poll() { return q.pollFirst(); }
5544 public E remove() { return q.removeFirst(); }
5545 public E peek() { return q.peekFirst(); }
5546 public E element() { return q.getFirst(); }
5547 public void clear() { q.clear(); }
5548 public int size() { return q.size(); }
5549 public boolean isEmpty() { return q.isEmpty(); }
5550 public boolean contains(Object o) { return q.contains(o); }
5551 public boolean remove(Object o) { return q.remove(o); }
5552 public Iterator<E> iterator() { return q.iterator(); }
5553 public Object[] toArray() { return q.toArray(); }
5554 public <T> T[] toArray(T[] a) { return q.toArray(a); }
5555 public String toString() { return q.toString(); }
5556 public boolean containsAll(Collection<?> c) {return q.containsAll(c);}
5557 public boolean removeAll(Collection<?> c) {return q.removeAll(c);}
5558 public boolean retainAll(Collection<?> c) {return q.retainAll(c);}
5559 // We use inherited addAll; forwarding addAll would be wrong
5560
5561 // Override default methods in Collection
5562 @Override
5563 public void forEach(Consumer<? super E> action) {q.forEach(action);}
5564 @Override
5565 public Spliterator<E> spliterator() {return q.spliterator();}
5566 @Override
5567 public boolean removeIf(Predicate<? super E> filter) {
5568 return q.removeIf(filter);
5569 }
5570 }
5571 }