1 /*
2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.util;
27 import java.io.Serializable;
28 import java.io.ObjectOutputStream;
29 import java.io.IOException;
30 import java.io.InvalidObjectException;
31 import java.lang.reflect.Array;
32 import java.util.function.BiConsumer;
33 import java.util.function.BiFunction;
34 import java.util.function.Consumer;
35 import java.util.function.Function;
36 import java.util.function.Predicate;
37 import java.util.function.UnaryOperator;
38
39 /**
40 * This class consists exclusively of static methods that operate on or return
41 * collections. It contains polymorphic algorithms that operate on
42 * collections, "wrappers", which return a new collection backed by a
43 * specified collection, and a few other odds and ends.
44 *
45 * <p>The methods of this class all throw a <tt>NullPointerException</tt>
46 * if the collections or class objects provided to them are null.
47 *
48 * <p>The documentation for the polymorphic algorithms contained in this class
49 * generally includes a brief description of the <i>implementation</i>. Such
50 * descriptions should be regarded as <i>implementation notes</i>, rather than
51 * parts of the <i>specification</i>. Implementors should feel free to
52 * substitute other algorithms, so long as the specification itself is adhered
53 * to. (For example, the algorithm used by <tt>sort</tt> does not have to be
54 * a mergesort, but it does have to be <i>stable</i>.)
55 *
56 * <p>The "destructive" algorithms contained in this class, that is, the
57 * algorithms that modify the collection on which they operate, are specified
58 * to throw <tt>UnsupportedOperationException</tt> if the collection does not
59 * support the appropriate mutation primitive(s), such as the <tt>set</tt>
60 * method. These algorithms may, but are not required to, throw this
61 * exception if an invocation would have no effect on the collection. For
62 * example, invoking the <tt>sort</tt> method on an unmodifiable list that is
63 * already sorted may or may not throw <tt>UnsupportedOperationException</tt>.
64 *
65 * <p>This class is a member of the
66 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
67 * Java Collections Framework</a>.
68 *
69 * @author Josh Bloch
70 * @author Neal Gafter
71 * @see Collection
72 * @see Set
73 * @see List
74 * @see Map
75 * @since 1.2
76 */
77
78 public class Collections {
79 // Suppresses default constructor, ensuring non-instantiability.
80 private Collections() {
81 }
82
83 // Algorithms
84
85 /*
86 * Tuning parameters for algorithms - Many of the List algorithms have
87 * two implementations, one of which is appropriate for RandomAccess
88 * lists, the other for "sequential." Often, the random access variant
89 * yields better performance on small sequential access lists. The
90 * tuning parameters below determine the cutoff point for what constitutes
91 * a "small" sequential access list for each algorithm. The values below
92 * were empirically determined to work well for LinkedList. Hopefully
93 * they should be reasonable for other sequential access List
94 * implementations. Those doing performance work on this code would
95 * do well to validate the values of these parameters from time to time.
96 * (The first word of each tuning parameter name is the algorithm to which
97 * it applies.)
98 */
99 private static final int BINARYSEARCH_THRESHOLD = 5000;
100 private static final int REVERSE_THRESHOLD = 18;
101 private static final int SHUFFLE_THRESHOLD = 5;
102 private static final int FILL_THRESHOLD = 25;
103 private static final int ROTATE_THRESHOLD = 100;
104 private static final int COPY_THRESHOLD = 10;
105 private static final int REPLACEALL_THRESHOLD = 11;
106 private static final int INDEXOFSUBLIST_THRESHOLD = 35;
107
108 /**
109 * Sorts the specified list into ascending order, according to the
110 * {@linkplain Comparable natural ordering} of its elements.
111 * All elements in the list must implement the {@link Comparable}
112 * interface. Furthermore, all elements in the list must be
113 * <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)}
114 * must not throw a {@code ClassCastException} for any elements
115 * {@code e1} and {@code e2} in the list).
116 *
117 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will
118 * not be reordered as a result of the sort.
119 *
120 * <p>The specified list must be modifiable, but need not be resizable.
121 *
122 * <p>Implementation note: This implementation is a stable, adaptive,
123 * iterative mergesort that requires far fewer than n lg(n) comparisons
124 * when the input array is partially sorted, while offering the
125 * performance of a traditional mergesort when the input array is
126 * randomly ordered. If the input array is nearly sorted, the
127 * implementation requires approximately n comparisons. Temporary
128 * storage requirements vary from a small constant for nearly sorted
129 * input arrays to n/2 object references for randomly ordered input
130 * arrays.
131 *
132 * <p>The implementation takes equal advantage of ascending and
133 * descending order in its input array, and can take advantage of
134 * ascending and descending order in different parts of the same
135 * input array. It is well-suited to merging two or more sorted arrays:
136 * simply concatenate the arrays and sort the resulting array.
137 *
138 * <p>The implementation was adapted from Tim Peters's list sort for Python
139 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
140 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
141 * Sorting and Information Theoretic Complexity", in Proceedings of the
142 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
143 * January 1993.
144 *
145 * <p>This implementation dumps the specified list into an array, sorts
146 * the array, and iterates over the list resetting each element
147 * from the corresponding position in the array. This avoids the
148 * n<sup>2</sup> log(n) performance that would result from attempting
149 * to sort a linked list in place.
150 *
151 * @param list the list to be sorted.
152 * @throws ClassCastException if the list contains elements that are not
153 * <i>mutually comparable</i> (for example, strings and integers).
154 * @throws UnsupportedOperationException if the specified list's
155 * list-iterator does not support the {@code set} operation.
156 * @throws IllegalArgumentException (optional) if the implementation
157 * detects that the natural ordering of the list elements is
158 * found to violate the {@link Comparable} contract
159 */
160 @SuppressWarnings("unchecked")
161 public static <T extends Comparable<? super T>> void sort(List<T> list) {
162 Object[] a = list.toArray();
163 Arrays.sort(a);
164 ListIterator<T> i = list.listIterator();
165 for (int j=0; j<a.length; j++) {
166 i.next();
167 i.set((T)a[j]);
168 }
169 }
170
171 /**
172 * Sorts the specified list according to the order induced by the
173 * specified comparator. All elements in the list must be <i>mutually
174 * comparable</i> using the specified comparator (that is,
175 * {@code c.compare(e1, e2)} must not throw a {@code ClassCastException}
176 * for any elements {@code e1} and {@code e2} in the list).
177 *
178 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will
179 * not be reordered as a result of the sort.
180 *
181 * <p>The specified list must be modifiable, but need not be resizable.
182 *
183 * <p>Implementation note: This implementation is a stable, adaptive,
184 * iterative mergesort that requires far fewer than n lg(n) comparisons
185 * when the input array is partially sorted, while offering the
186 * performance of a traditional mergesort when the input array is
187 * randomly ordered. If the input array is nearly sorted, the
188 * implementation requires approximately n comparisons. Temporary
189 * storage requirements vary from a small constant for nearly sorted
190 * input arrays to n/2 object references for randomly ordered input
191 * arrays.
192 *
193 * <p>The implementation takes equal advantage of ascending and
194 * descending order in its input array, and can take advantage of
195 * ascending and descending order in different parts of the same
196 * input array. It is well-suited to merging two or more sorted arrays:
197 * simply concatenate the arrays and sort the resulting array.
198 *
199 * <p>The implementation was adapted from Tim Peters's list sort for Python
200 * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
201 * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
202 * Sorting and Information Theoretic Complexity", in Proceedings of the
203 * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
204 * January 1993.
205 *
206 * <p>This implementation dumps the specified list into an array, sorts
207 * the array, and iterates over the list resetting each element
208 * from the corresponding position in the array. This avoids the
209 * n<sup>2</sup> log(n) performance that would result from attempting
210 * to sort a linked list in place.
211 *
212 * @param list the list to be sorted.
213 * @param c the comparator to determine the order of the list. A
214 * {@code null} value indicates that the elements' <i>natural
215 * ordering</i> should be used.
216 * @throws ClassCastException if the list contains elements that are not
217 * <i>mutually comparable</i> using the specified comparator.
218 * @throws UnsupportedOperationException if the specified list's
219 * list-iterator does not support the {@code set} operation.
220 * @throws IllegalArgumentException (optional) if the comparator is
221 * found to violate the {@link Comparator} contract
222 */
223 @SuppressWarnings({"unchecked", "rawtypes"})
224 public static <T> void sort(List<T> list, Comparator<? super T> c) {
225 Object[] a = list.toArray();
226 Arrays.sort(a, (Comparator)c);
227 ListIterator<T> i = list.listIterator();
228 for (int j=0; j<a.length; j++) {
229 i.next();
230 i.set((T)a[j]);
231 }
232 }
233
234
235 /**
236 * Searches the specified list for the specified object using the binary
237 * search algorithm. The list must be sorted into ascending order
238 * according to the {@linkplain Comparable natural ordering} of its
239 * elements (as by the {@link #sort(List)} method) prior to making this
240 * call. If it is not sorted, the results are undefined. If the list
241 * contains multiple elements equal to the specified object, there is no
242 * guarantee which one will be found.
243 *
244 * <p>This method runs in log(n) time for a "random access" list (which
245 * provides near-constant-time positional access). If the specified list
246 * does not implement the {@link RandomAccess} interface and is large,
247 * this method will do an iterator-based binary search that performs
248 * O(n) link traversals and O(log n) element comparisons.
249 *
250 * @param list the list to be searched.
251 * @param key the key to be searched for.
252 * @return the index of the search key, if it is contained in the list;
253 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
254 * <i>insertion point</i> is defined as the point at which the
255 * key would be inserted into the list: the index of the first
256 * element greater than the key, or <tt>list.size()</tt> if all
257 * elements in the list are less than the specified key. Note
258 * that this guarantees that the return value will be >= 0 if
259 * and only if the key is found.
260 * @throws ClassCastException if the list contains elements that are not
261 * <i>mutually comparable</i> (for example, strings and
262 * integers), or the search key is not mutually comparable
263 * with the elements of the list.
264 */
265 public static <T>
266 int binarySearch(List<? extends Comparable<? super T>> list, T key) {
267 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
268 return Collections.indexedBinarySearch(list, key);
269 else
270 return Collections.iteratorBinarySearch(list, key);
271 }
272
273 private static <T>
274 int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) {
275 int low = 0;
276 int high = list.size()-1;
277
278 while (low <= high) {
279 int mid = (low + high) >>> 1;
280 Comparable<? super T> midVal = list.get(mid);
281 int cmp = midVal.compareTo(key);
282
283 if (cmp < 0)
284 low = mid + 1;
285 else if (cmp > 0)
286 high = mid - 1;
287 else
288 return mid; // key found
289 }
290 return -(low + 1); // key not found
291 }
292
293 private static <T>
294 int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key)
295 {
296 int low = 0;
297 int high = list.size()-1;
298 ListIterator<? extends Comparable<? super T>> i = list.listIterator();
299
300 while (low <= high) {
301 int mid = (low + high) >>> 1;
302 Comparable<? super T> midVal = get(i, mid);
303 int cmp = midVal.compareTo(key);
304
305 if (cmp < 0)
306 low = mid + 1;
307 else if (cmp > 0)
308 high = mid - 1;
309 else
310 return mid; // key found
311 }
312 return -(low + 1); // key not found
313 }
314
315 /**
316 * Gets the ith element from the given list by repositioning the specified
317 * list listIterator.
318 */
319 private static <T> T get(ListIterator<? extends T> i, int index) {
320 T obj = null;
321 int pos = i.nextIndex();
322 if (pos <= index) {
323 do {
324 obj = i.next();
325 } while (pos++ < index);
326 } else {
327 do {
328 obj = i.previous();
329 } while (--pos > index);
330 }
331 return obj;
332 }
333
334 /**
335 * Searches the specified list for the specified object using the binary
336 * search algorithm. The list must be sorted into ascending order
337 * according to the specified comparator (as by the
338 * {@link #sort(List, Comparator) sort(List, Comparator)}
339 * method), prior to making this call. If it is
340 * not sorted, the results are undefined. If the list contains multiple
341 * elements equal to the specified object, there is no guarantee which one
342 * will be found.
343 *
344 * <p>This method runs in log(n) time for a "random access" list (which
345 * provides near-constant-time positional access). If the specified list
346 * does not implement the {@link RandomAccess} interface and is large,
347 * this method will do an iterator-based binary search that performs
348 * O(n) link traversals and O(log n) element comparisons.
349 *
350 * @param list the list to be searched.
351 * @param key the key to be searched for.
352 * @param c the comparator by which the list is ordered.
353 * A <tt>null</tt> value indicates that the elements'
354 * {@linkplain Comparable natural ordering} should be used.
355 * @return the index of the search key, if it is contained in the list;
356 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The
357 * <i>insertion point</i> is defined as the point at which the
358 * key would be inserted into the list: the index of the first
359 * element greater than the key, or <tt>list.size()</tt> if all
360 * elements in the list are less than the specified key. Note
361 * that this guarantees that the return value will be >= 0 if
362 * and only if the key is found.
363 * @throws ClassCastException if the list contains elements that are not
364 * <i>mutually comparable</i> using the specified comparator,
365 * or the search key is not mutually comparable with the
366 * elements of the list using this comparator.
367 */
368 @SuppressWarnings("unchecked")
369 public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) {
370 if (c==null)
371 return binarySearch((List<? extends Comparable<? super T>>) list, key);
372
373 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD)
374 return Collections.indexedBinarySearch(list, key, c);
375 else
376 return Collections.iteratorBinarySearch(list, key, c);
377 }
378
379 private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
380 int low = 0;
381 int high = l.size()-1;
382
383 while (low <= high) {
384 int mid = (low + high) >>> 1;
385 T midVal = l.get(mid);
386 int cmp = c.compare(midVal, key);
387
388 if (cmp < 0)
389 low = mid + 1;
390 else if (cmp > 0)
391 high = mid - 1;
392 else
393 return mid; // key found
394 }
395 return -(low + 1); // key not found
396 }
397
398 private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) {
399 int low = 0;
400 int high = l.size()-1;
401 ListIterator<? extends T> i = l.listIterator();
402
403 while (low <= high) {
404 int mid = (low + high) >>> 1;
405 T midVal = get(i, mid);
406 int cmp = c.compare(midVal, key);
407
408 if (cmp < 0)
409 low = mid + 1;
410 else if (cmp > 0)
411 high = mid - 1;
412 else
413 return mid; // key found
414 }
415 return -(low + 1); // key not found
416 }
417
418 /**
419 * Reverses the order of the elements in the specified list.<p>
420 *
421 * This method runs in linear time.
422 *
423 * @param list the list whose elements are to be reversed.
424 * @throws UnsupportedOperationException if the specified list or
425 * its list-iterator does not support the <tt>set</tt> operation.
426 */
427 @SuppressWarnings({"rawtypes", "unchecked"})
428 public static void reverse(List<?> list) {
429 int size = list.size();
430 if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) {
431 for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--)
432 swap(list, i, j);
433 } else {
434 // instead of using a raw type here, it's possible to capture
435 // the wildcard but it will require a call to a supplementary
436 // private method
437 ListIterator fwd = list.listIterator();
438 ListIterator rev = list.listIterator(size);
439 for (int i=0, mid=list.size()>>1; i<mid; i++) {
440 Object tmp = fwd.next();
441 fwd.set(rev.previous());
442 rev.set(tmp);
443 }
444 }
445 }
446
447 /**
448 * Randomly permutes the specified list using a default source of
449 * randomness. All permutations occur with approximately equal
450 * likelihood.
451 *
452 * <p>The hedge "approximately" is used in the foregoing description because
453 * default source of randomness is only approximately an unbiased source
454 * of independently chosen bits. If it were a perfect source of randomly
455 * chosen bits, then the algorithm would choose permutations with perfect
456 * uniformity.
457 *
458 * <p>This implementation traverses the list backwards, from the last
459 * element up to the second, repeatedly swapping a randomly selected element
460 * into the "current position". Elements are randomly selected from the
461 * portion of the list that runs from the first element to the current
462 * position, inclusive.
463 *
464 * <p>This method runs in linear time. If the specified list does not
465 * implement the {@link RandomAccess} interface and is large, this
466 * implementation dumps the specified list into an array before shuffling
467 * it, and dumps the shuffled array back into the list. This avoids the
468 * quadratic behavior that would result from shuffling a "sequential
469 * access" list in place.
470 *
471 * @param list the list to be shuffled.
472 * @throws UnsupportedOperationException if the specified list or
473 * its list-iterator does not support the <tt>set</tt> operation.
474 */
475 public static void shuffle(List<?> list) {
476 Random rnd = r;
477 if (rnd == null)
478 r = rnd = new Random(); // harmless race.
479 shuffle(list, rnd);
480 }
481
482 private static Random r;
483
484 /**
485 * Randomly permute the specified list using the specified source of
486 * randomness. All permutations occur with equal likelihood
487 * assuming that the source of randomness is fair.<p>
488 *
489 * This implementation traverses the list backwards, from the last element
490 * up to the second, repeatedly swapping a randomly selected element into
491 * the "current position". Elements are randomly selected from the
492 * portion of the list that runs from the first element to the current
493 * position, inclusive.<p>
494 *
495 * This method runs in linear time. If the specified list does not
496 * implement the {@link RandomAccess} interface and is large, this
497 * implementation dumps the specified list into an array before shuffling
498 * it, and dumps the shuffled array back into the list. This avoids the
499 * quadratic behavior that would result from shuffling a "sequential
500 * access" list in place.
501 *
502 * @param list the list to be shuffled.
503 * @param rnd the source of randomness to use to shuffle the list.
504 * @throws UnsupportedOperationException if the specified list or its
505 * list-iterator does not support the <tt>set</tt> operation.
506 */
507 @SuppressWarnings({"rawtypes", "unchecked"})
508 public static void shuffle(List<?> list, Random rnd) {
509 int size = list.size();
510 if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) {
511 for (int i=size; i>1; i--)
512 swap(list, i-1, rnd.nextInt(i));
513 } else {
514 Object arr[] = list.toArray();
515
516 // Shuffle array
517 for (int i=size; i>1; i--)
518 swap(arr, i-1, rnd.nextInt(i));
519
520 // Dump array back into list
521 // instead of using a raw type here, it's possible to capture
522 // the wildcard but it will require a call to a supplementary
523 // private method
524 ListIterator it = list.listIterator();
525 for (int i=0; i<arr.length; i++) {
526 it.next();
527 it.set(arr[i]);
528 }
529 }
530 }
531
532 /**
533 * Swaps the elements at the specified positions in the specified list.
534 * (If the specified positions are equal, invoking this method leaves
535 * the list unchanged.)
536 *
537 * @param list The list in which to swap elements.
538 * @param i the index of one element to be swapped.
539 * @param j the index of the other element to be swapped.
540 * @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt>
541 * is out of range (i < 0 || i >= list.size()
542 * || j < 0 || j >= list.size()).
543 * @since 1.4
544 */
545 @SuppressWarnings({"rawtypes", "unchecked"})
546 public static void swap(List<?> list, int i, int j) {
547 // instead of using a raw type here, it's possible to capture
548 // the wildcard but it will require a call to a supplementary
549 // private method
550 final List l = list;
551 l.set(i, l.set(j, l.get(i)));
552 }
553
554 /**
555 * Swaps the two specified elements in the specified array.
556 */
557 private static void swap(Object[] arr, int i, int j) {
558 Object tmp = arr[i];
559 arr[i] = arr[j];
560 arr[j] = tmp;
561 }
562
563 /**
564 * Replaces all of the elements of the specified list with the specified
565 * element. <p>
566 *
567 * This method runs in linear time.
568 *
569 * @param list the list to be filled with the specified element.
570 * @param obj The element with which to fill the specified list.
571 * @throws UnsupportedOperationException if the specified list or its
572 * list-iterator does not support the <tt>set</tt> operation.
573 */
574 public static <T> void fill(List<? super T> list, T obj) {
575 int size = list.size();
576
577 if (size < FILL_THRESHOLD || list instanceof RandomAccess) {
578 for (int i=0; i<size; i++)
579 list.set(i, obj);
580 } else {
581 ListIterator<? super T> itr = list.listIterator();
582 for (int i=0; i<size; i++) {
583 itr.next();
584 itr.set(obj);
585 }
586 }
587 }
588
589 /**
590 * Copies all of the elements from one list into another. After the
591 * operation, the index of each copied element in the destination list
592 * will be identical to its index in the source list. The destination
593 * list must be at least as long as the source list. If it is longer, the
594 * remaining elements in the destination list are unaffected. <p>
595 *
596 * This method runs in linear time.
597 *
598 * @param dest The destination list.
599 * @param src The source list.
600 * @throws IndexOutOfBoundsException if the destination list is too small
601 * to contain the entire source List.
602 * @throws UnsupportedOperationException if the destination list's
603 * list-iterator does not support the <tt>set</tt> operation.
604 */
605 public static <T> void copy(List<? super T> dest, List<? extends T> src) {
606 int srcSize = src.size();
607 if (srcSize > dest.size())
608 throw new IndexOutOfBoundsException("Source does not fit in dest");
609
610 if (srcSize < COPY_THRESHOLD ||
611 (src instanceof RandomAccess && dest instanceof RandomAccess)) {
612 for (int i=0; i<srcSize; i++)
613 dest.set(i, src.get(i));
614 } else {
615 ListIterator<? super T> di=dest.listIterator();
616 ListIterator<? extends T> si=src.listIterator();
617 for (int i=0; i<srcSize; i++) {
618 di.next();
619 di.set(si.next());
620 }
621 }
622 }
623
624 /**
625 * Returns the minimum element of the given collection, according to the
626 * <i>natural ordering</i> of its elements. All elements in the
627 * collection must implement the <tt>Comparable</tt> interface.
628 * Furthermore, all elements in the collection must be <i>mutually
629 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
630 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
631 * <tt>e2</tt> in the collection).<p>
632 *
633 * This method iterates over the entire collection, hence it requires
634 * time proportional to the size of the collection.
635 *
636 * @param coll the collection whose minimum element is to be determined.
637 * @return the minimum element of the given collection, according
638 * to the <i>natural ordering</i> of its elements.
639 * @throws ClassCastException if the collection contains elements that are
640 * not <i>mutually comparable</i> (for example, strings and
641 * integers).
642 * @throws NoSuchElementException if the collection is empty.
643 * @see Comparable
644 */
645 public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) {
646 Iterator<? extends T> i = coll.iterator();
647 T candidate = i.next();
648
649 while (i.hasNext()) {
650 T next = i.next();
651 if (next.compareTo(candidate) < 0)
652 candidate = next;
653 }
654 return candidate;
655 }
656
657 /**
658 * Returns the minimum element of the given collection, according to the
659 * order induced by the specified comparator. All elements in the
660 * collection must be <i>mutually comparable</i> by the specified
661 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
662 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
663 * <tt>e2</tt> in the collection).<p>
664 *
665 * This method iterates over the entire collection, hence it requires
666 * time proportional to the size of the collection.
667 *
668 * @param coll the collection whose minimum element is to be determined.
669 * @param comp the comparator with which to determine the minimum element.
670 * A <tt>null</tt> value indicates that the elements' <i>natural
671 * ordering</i> should be used.
672 * @return the minimum element of the given collection, according
673 * to the specified comparator.
674 * @throws ClassCastException if the collection contains elements that are
675 * not <i>mutually comparable</i> using the specified comparator.
676 * @throws NoSuchElementException if the collection is empty.
677 * @see Comparable
678 */
679 @SuppressWarnings({"unchecked", "rawtypes"})
680 public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) {
681 if (comp==null)
682 return (T)min((Collection) coll);
683
684 Iterator<? extends T> i = coll.iterator();
685 T candidate = i.next();
686
687 while (i.hasNext()) {
688 T next = i.next();
689 if (comp.compare(next, candidate) < 0)
690 candidate = next;
691 }
692 return candidate;
693 }
694
695 /**
696 * Returns the maximum element of the given collection, according to the
697 * <i>natural ordering</i> of its elements. All elements in the
698 * collection must implement the <tt>Comparable</tt> interface.
699 * Furthermore, all elements in the collection must be <i>mutually
700 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a
701 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
702 * <tt>e2</tt> in the collection).<p>
703 *
704 * This method iterates over the entire collection, hence it requires
705 * time proportional to the size of the collection.
706 *
707 * @param coll the collection whose maximum element is to be determined.
708 * @return the maximum element of the given collection, according
709 * to the <i>natural ordering</i> of its elements.
710 * @throws ClassCastException if the collection contains elements that are
711 * not <i>mutually comparable</i> (for example, strings and
712 * integers).
713 * @throws NoSuchElementException if the collection is empty.
714 * @see Comparable
715 */
716 public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) {
717 Iterator<? extends T> i = coll.iterator();
718 T candidate = i.next();
719
720 while (i.hasNext()) {
721 T next = i.next();
722 if (next.compareTo(candidate) > 0)
723 candidate = next;
724 }
725 return candidate;
726 }
727
728 /**
729 * Returns the maximum element of the given collection, according to the
730 * order induced by the specified comparator. All elements in the
731 * collection must be <i>mutually comparable</i> by the specified
732 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a
733 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and
734 * <tt>e2</tt> in the collection).<p>
735 *
736 * This method iterates over the entire collection, hence it requires
737 * time proportional to the size of the collection.
738 *
739 * @param coll the collection whose maximum element is to be determined.
740 * @param comp the comparator with which to determine the maximum element.
741 * A <tt>null</tt> value indicates that the elements' <i>natural
742 * ordering</i> should be used.
743 * @return the maximum element of the given collection, according
744 * to the specified comparator.
745 * @throws ClassCastException if the collection contains elements that are
746 * not <i>mutually comparable</i> using the specified comparator.
747 * @throws NoSuchElementException if the collection is empty.
748 * @see Comparable
749 */
750 @SuppressWarnings({"unchecked", "rawtypes"})
751 public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) {
752 if (comp==null)
753 return (T)max((Collection) coll);
754
755 Iterator<? extends T> i = coll.iterator();
756 T candidate = i.next();
757
758 while (i.hasNext()) {
759 T next = i.next();
760 if (comp.compare(next, candidate) > 0)
761 candidate = next;
762 }
763 return candidate;
764 }
765
766 /**
767 * Rotates the elements in the specified list by the specified distance.
768 * After calling this method, the element at index <tt>i</tt> will be
769 * the element previously at index <tt>(i - distance)</tt> mod
770 * <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt>
771 * and <tt>list.size()-1</tt>, inclusive. (This method has no effect on
772 * the size of the list.)
773 *
774 * <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>.
775 * After invoking <tt>Collections.rotate(list, 1)</tt> (or
776 * <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise
777 * <tt>[s, t, a, n, k]</tt>.
778 *
779 * <p>Note that this method can usefully be applied to sublists to
780 * move one or more elements within a list while preserving the
781 * order of the remaining elements. For example, the following idiom
782 * moves the element at index <tt>j</tt> forward to position
783 * <tt>k</tt> (which must be greater than or equal to <tt>j</tt>):
784 * <pre>
785 * Collections.rotate(list.subList(j, k+1), -1);
786 * </pre>
787 * To make this concrete, suppose <tt>list</tt> comprises
788 * <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt>
789 * (<tt>b</tt>) forward two positions, perform the following invocation:
790 * <pre>
791 * Collections.rotate(l.subList(1, 4), -1);
792 * </pre>
793 * The resulting list is <tt>[a, c, d, b, e]</tt>.
794 *
795 * <p>To move more than one element forward, increase the absolute value
796 * of the rotation distance. To move elements backward, use a positive
797 * shift distance.
798 *
799 * <p>If the specified list is small or implements the {@link
800 * RandomAccess} interface, this implementation exchanges the first
801 * element into the location it should go, and then repeatedly exchanges
802 * the displaced element into the location it should go until a displaced
803 * element is swapped into the first element. If necessary, the process
804 * is repeated on the second and successive elements, until the rotation
805 * is complete. If the specified list is large and doesn't implement the
806 * <tt>RandomAccess</tt> interface, this implementation breaks the
807 * list into two sublist views around index <tt>-distance mod size</tt>.
808 * Then the {@link #reverse(List)} method is invoked on each sublist view,
809 * and finally it is invoked on the entire list. For a more complete
810 * description of both algorithms, see Section 2.3 of Jon Bentley's
811 * <i>Programming Pearls</i> (Addison-Wesley, 1986).
812 *
813 * @param list the list to be rotated.
814 * @param distance the distance to rotate the list. There are no
815 * constraints on this value; it may be zero, negative, or
816 * greater than <tt>list.size()</tt>.
817 * @throws UnsupportedOperationException if the specified list or
818 * its list-iterator does not support the <tt>set</tt> operation.
819 * @since 1.4
820 */
821 public static void rotate(List<?> list, int distance) {
822 if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD)
823 rotate1(list, distance);
824 else
825 rotate2(list, distance);
826 }
827
828 private static <T> void rotate1(List<T> list, int distance) {
829 int size = list.size();
830 if (size == 0)
831 return;
832 distance = distance % size;
833 if (distance < 0)
834 distance += size;
835 if (distance == 0)
836 return;
837
838 for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) {
839 T displaced = list.get(cycleStart);
840 int i = cycleStart;
841 do {
842 i += distance;
843 if (i >= size)
844 i -= size;
845 displaced = list.set(i, displaced);
846 nMoved ++;
847 } while (i != cycleStart);
848 }
849 }
850
851 private static void rotate2(List<?> list, int distance) {
852 int size = list.size();
853 if (size == 0)
854 return;
855 int mid = -distance % size;
856 if (mid < 0)
857 mid += size;
858 if (mid == 0)
859 return;
860
861 reverse(list.subList(0, mid));
862 reverse(list.subList(mid, size));
863 reverse(list);
864 }
865
866 /**
867 * Replaces all occurrences of one specified value in a list with another.
868 * More formally, replaces with <tt>newVal</tt> each element <tt>e</tt>
869 * in <tt>list</tt> such that
870 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
871 * (This method has no effect on the size of the list.)
872 *
873 * @param list the list in which replacement is to occur.
874 * @param oldVal the old value to be replaced.
875 * @param newVal the new value with which <tt>oldVal</tt> is to be
876 * replaced.
877 * @return <tt>true</tt> if <tt>list</tt> contained one or more elements
878 * <tt>e</tt> such that
879 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>.
880 * @throws UnsupportedOperationException if the specified list or
881 * its list-iterator does not support the <tt>set</tt> operation.
882 * @since 1.4
883 */
884 public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) {
885 boolean result = false;
886 int size = list.size();
887 if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) {
888 if (oldVal==null) {
889 for (int i=0; i<size; i++) {
890 if (list.get(i)==null) {
891 list.set(i, newVal);
892 result = true;
893 }
894 }
895 } else {
896 for (int i=0; i<size; i++) {
897 if (oldVal.equals(list.get(i))) {
898 list.set(i, newVal);
899 result = true;
900 }
901 }
902 }
903 } else {
904 ListIterator<T> itr=list.listIterator();
905 if (oldVal==null) {
906 for (int i=0; i<size; i++) {
907 if (itr.next()==null) {
908 itr.set(newVal);
909 result = true;
910 }
911 }
912 } else {
913 for (int i=0; i<size; i++) {
914 if (oldVal.equals(itr.next())) {
915 itr.set(newVal);
916 result = true;
917 }
918 }
919 }
920 }
921 return result;
922 }
923
924 /**
925 * Returns the starting position of the first occurrence of the specified
926 * target list within the specified source list, or -1 if there is no
927 * such occurrence. More formally, returns the lowest index <tt>i</tt>
928 * such that {@code source.subList(i, i+target.size()).equals(target)},
929 * or -1 if there is no such index. (Returns -1 if
930 * {@code target.size() > source.size()})
931 *
932 * <p>This implementation uses the "brute force" technique of scanning
933 * over the source list, looking for a match with the target at each
934 * location in turn.
935 *
936 * @param source the list in which to search for the first occurrence
937 * of <tt>target</tt>.
938 * @param target the list to search for as a subList of <tt>source</tt>.
939 * @return the starting position of the first occurrence of the specified
940 * target list within the specified source list, or -1 if there
941 * is no such occurrence.
942 * @since 1.4
943 */
944 public static int indexOfSubList(List<?> source, List<?> target) {
945 int sourceSize = source.size();
946 int targetSize = target.size();
947 int maxCandidate = sourceSize - targetSize;
948
949 if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
950 (source instanceof RandomAccess&&target instanceof RandomAccess)) {
951 nextCand:
952 for (int candidate = 0; candidate <= maxCandidate; candidate++) {
953 for (int i=0, j=candidate; i<targetSize; i++, j++)
954 if (!eq(target.get(i), source.get(j)))
955 continue nextCand; // Element mismatch, try next cand
956 return candidate; // All elements of candidate matched target
957 }
958 } else { // Iterator version of above algorithm
959 ListIterator<?> si = source.listIterator();
960 nextCand:
961 for (int candidate = 0; candidate <= maxCandidate; candidate++) {
962 ListIterator<?> ti = target.listIterator();
963 for (int i=0; i<targetSize; i++) {
964 if (!eq(ti.next(), si.next())) {
965 // Back up source iterator to next candidate
966 for (int j=0; j<i; j++)
967 si.previous();
968 continue nextCand;
969 }
970 }
971 return candidate;
972 }
973 }
974 return -1; // No candidate matched the target
975 }
976
977 /**
978 * Returns the starting position of the last occurrence of the specified
979 * target list within the specified source list, or -1 if there is no such
980 * occurrence. More formally, returns the highest index <tt>i</tt>
981 * such that {@code source.subList(i, i+target.size()).equals(target)},
982 * or -1 if there is no such index. (Returns -1 if
983 * {@code target.size() > source.size()})
984 *
985 * <p>This implementation uses the "brute force" technique of iterating
986 * over the source list, looking for a match with the target at each
987 * location in turn.
988 *
989 * @param source the list in which to search for the last occurrence
990 * of <tt>target</tt>.
991 * @param target the list to search for as a subList of <tt>source</tt>.
992 * @return the starting position of the last occurrence of the specified
993 * target list within the specified source list, or -1 if there
994 * is no such occurrence.
995 * @since 1.4
996 */
997 public static int lastIndexOfSubList(List<?> source, List<?> target) {
998 int sourceSize = source.size();
999 int targetSize = target.size();
1000 int maxCandidate = sourceSize - targetSize;
1001
1002 if (sourceSize < INDEXOFSUBLIST_THRESHOLD ||
1003 source instanceof RandomAccess) { // Index access version
1004 nextCand:
1005 for (int candidate = maxCandidate; candidate >= 0; candidate--) {
1006 for (int i=0, j=candidate; i<targetSize; i++, j++)
1007 if (!eq(target.get(i), source.get(j)))
1008 continue nextCand; // Element mismatch, try next cand
1009 return candidate; // All elements of candidate matched target
1010 }
1011 } else { // Iterator version of above algorithm
1012 if (maxCandidate < 0)
1013 return -1;
1014 ListIterator<?> si = source.listIterator(maxCandidate);
1015 nextCand:
1016 for (int candidate = maxCandidate; candidate >= 0; candidate--) {
1017 ListIterator<?> ti = target.listIterator();
1018 for (int i=0; i<targetSize; i++) {
1019 if (!eq(ti.next(), si.next())) {
1020 if (candidate != 0) {
1021 // Back up source iterator to next candidate
1022 for (int j=0; j<=i+1; j++)
1023 si.previous();
1024 }
1025 continue nextCand;
1026 }
1027 }
1028 return candidate;
1029 }
1030 }
1031 return -1; // No candidate matched the target
1032 }
1033
1034
1035 // Unmodifiable Wrappers
1036
1037 /**
1038 * Returns an unmodifiable view of the specified collection. This method
1039 * allows modules to provide users with "read-only" access to internal
1040 * collections. Query operations on the returned collection "read through"
1041 * to the specified collection, and attempts to modify the returned
1042 * collection, whether direct or via its iterator, result in an
1043 * <tt>UnsupportedOperationException</tt>.<p>
1044 *
1045 * The returned collection does <i>not</i> pass the hashCode and equals
1046 * operations through to the backing collection, but relies on
1047 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This
1048 * is necessary to preserve the contracts of these operations in the case
1049 * that the backing collection is a set or a list.<p>
1050 *
1051 * The returned collection will be serializable if the specified collection
1052 * is serializable.
1053 *
1054 * @param c the collection for which an unmodifiable view is to be
1055 * returned.
1056 * @return an unmodifiable view of the specified collection.
1057 */
1058 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
1059 return new UnmodifiableCollection<>(c);
1060 }
1061
1062 /**
1063 * @serial include
1064 */
1065 static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
1066 private static final long serialVersionUID = 1820017752578914078L;
1067
1068 final Collection<? extends E> c;
1069
1070 UnmodifiableCollection(Collection<? extends E> c) {
1071 if (c==null)
1072 throw new NullPointerException();
1073 this.c = c;
1074 }
1075
1076 public int size() {return c.size();}
1077 public boolean isEmpty() {return c.isEmpty();}
1078 public boolean contains(Object o) {return c.contains(o);}
1079 public Object[] toArray() {return c.toArray();}
1080 public <T> T[] toArray(T[] a) {return c.toArray(a);}
1081 public String toString() {return c.toString();}
1082
1083 public Iterator<E> iterator() {
1084 return new Iterator<E>() {
1085 private final Iterator<? extends E> i = c.iterator();
1086
1087 public boolean hasNext() {return i.hasNext();}
1088 public E next() {return i.next();}
1089 public void remove() {
1090 throw new UnsupportedOperationException();
1091 }
1092 @Override
1093 public void forEachRemaining(Consumer<? super E> action) {
1094 // Use backing collection version
1095 i.forEachRemaining(action);
1096 }
1097 };
1098 }
1099
1100 public boolean add(E e) {
1101 throw new UnsupportedOperationException();
1102 }
1103 public boolean remove(Object o) {
1104 throw new UnsupportedOperationException();
1105 }
1106
1107 public boolean containsAll(Collection<?> coll) {
1108 return c.containsAll(coll);
1109 }
1110 public boolean addAll(Collection<? extends E> coll) {
1111 throw new UnsupportedOperationException();
1112 }
1113 public boolean removeAll(Collection<?> coll) {
1114 throw new UnsupportedOperationException();
1115 }
1116 public boolean retainAll(Collection<?> coll) {
1117 throw new UnsupportedOperationException();
1118 }
1119 public void clear() {
1120 throw new UnsupportedOperationException();
1121 }
1122
1123 // Override default methods in Collection
1124 @Override
1125 public void forEach(Consumer<? super E> action) {
1126 c.forEach(action);
1127 }
1128 @Override
1129 public boolean removeIf(Predicate<? super E> filter) {
1130 throw new UnsupportedOperationException();
1131 }
1132 @Override
1133 public Spliterator<E> spliterator() {
1134 return (Spliterator<E>)c.spliterator();
1135 }
1136
1137 }
1138
1139 /**
1140 * Returns an unmodifiable view of the specified set. This method allows
1141 * modules to provide users with "read-only" access to internal sets.
1142 * Query operations on the returned set "read through" to the specified
1143 * set, and attempts to modify the returned set, whether direct or via its
1144 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p>
1145 *
1146 * The returned set will be serializable if the specified set
1147 * is serializable.
1148 *
1149 * @param s the set for which an unmodifiable view is to be returned.
1150 * @return an unmodifiable view of the specified set.
1151 */
1152 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
1153 return new UnmodifiableSet<>(s);
1154 }
1155
1156 /**
1157 * @serial include
1158 */
1159 static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
1160 implements Set<E>, Serializable {
1161 private static final long serialVersionUID = -9215047833775013803L;
1162
1163 UnmodifiableSet(Set<? extends E> s) {super(s);}
1164 public boolean equals(Object o) {return o == this || c.equals(o);}
1165 public int hashCode() {return c.hashCode();}
1166 }
1167
1168 /**
1169 * Returns an unmodifiable view of the specified sorted set. This method
1170 * allows modules to provide users with "read-only" access to internal
1171 * sorted sets. Query operations on the returned sorted set "read
1172 * through" to the specified sorted set. Attempts to modify the returned
1173 * sorted set, whether direct, via its iterator, or via its
1174 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in
1175 * an <tt>UnsupportedOperationException</tt>.<p>
1176 *
1177 * The returned sorted set will be serializable if the specified sorted set
1178 * is serializable.
1179 *
1180 * @param s the sorted set for which an unmodifiable view is to be
1181 * returned.
1182 * @return an unmodifiable view of the specified sorted set.
1183 */
1184 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
1185 return new UnmodifiableSortedSet<>(s);
1186 }
1187
1188 /**
1189 * @serial include
1190 */
1191 static class UnmodifiableSortedSet<E>
1192 extends UnmodifiableSet<E>
1193 implements SortedSet<E>, Serializable {
1194 private static final long serialVersionUID = -4929149591599911165L;
1195 private final SortedSet<E> ss;
1196
1197 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
1198
1199 public Comparator<? super E> comparator() {return ss.comparator();}
1200
1201 public SortedSet<E> subSet(E fromElement, E toElement) {
1202 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
1203 }
1204 public SortedSet<E> headSet(E toElement) {
1205 return new UnmodifiableSortedSet<>(ss.headSet(toElement));
1206 }
1207 public SortedSet<E> tailSet(E fromElement) {
1208 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
1209 }
1210
1211 public E first() {return ss.first();}
1212 public E last() {return ss.last();}
1213 }
1214
1215 /**
1216 * Returns an unmodifiable view of the specified navigable set. This method
1217 * allows modules to provide users with "read-only" access to internal
1218 * navigable sets. Query operations on the returned navigable set "read
1219 * through" to the specified navigable set. Attempts to modify the returned
1220 * navigable set, whether direct, via its iterator, or via its
1221 * {@code subSet}, {@code headSet}, or {@code tailSet} views, result in
1222 * an {@code UnsupportedOperationException}.<p>
1223 *
1224 * The returned navigable set will be serializable if the specified
1225 * navigable set is serializable.
1226 *
1227 * @param s the navigable set for which an unmodifiable view is to be
1228 * returned
1229 * @return an unmodifiable view of the specified navigable set
1230 * @since 1.8
1231 */
1232 public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
1233 return new UnmodifiableNavigableSet<>(s);
1234 }
1235
1236 /**
1237 * Wraps a navigable set and disables all of the mutative operations.
1238 *
1239 * @param <E> type of elements
1240 * @serial include
1241 */
1242 static class UnmodifiableNavigableSet<E>
1243 extends UnmodifiableSortedSet<E>
1244 implements NavigableSet<E>, Serializable {
1245
1246 private static final long serialVersionUID = -6027448201786391929L;
1247
1248 /**
1249 * A singleton empty unmodifiable navigable set used for
1250 * {@link #emptyNavigableSet()}.
1251 *
1252 * @param <E> type of elements, if there were any, and bounds
1253 */
1254 private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E>
1255 implements Serializable {
1256 private static final long serialVersionUID = -6291252904449939134L;
1257
1258 public EmptyNavigableSet() {
1259 super(new TreeSet<E>());
1260 }
1261
1262 private Object readResolve() { return EMPTY_NAVIGABLE_SET; }
1263 }
1264
1265 @SuppressWarnings("rawtypes")
1266 private static final NavigableSet<?> EMPTY_NAVIGABLE_SET =
1267 new EmptyNavigableSet<>();
1268
1269 /**
1270 * The instance we are protecting.
1271 */
1272 private final NavigableSet<E> ns;
1273
1274 UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;}
1275
1276 public E lower(E e) { return ns.lower(e); }
1277 public E floor(E e) { return ns.floor(e); }
1278 public E ceiling(E e) { return ns.ceiling(e); }
1279 public E higher(E e) { return ns.higher(e); }
1280 public E pollFirst() { throw new UnsupportedOperationException(); }
1281 public E pollLast() { throw new UnsupportedOperationException(); }
1282 public NavigableSet<E> descendingSet()
1283 { return new UnmodifiableNavigableSet<>(ns.descendingSet()); }
1284 public Iterator<E> descendingIterator()
1285 { return descendingSet().iterator(); }
1286
1287 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
1288 return new UnmodifiableNavigableSet<>(
1289 ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
1290 }
1291
1292 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
1293 return new UnmodifiableNavigableSet<>(
1294 ns.headSet(toElement, inclusive));
1295 }
1296
1297 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
1298 return new UnmodifiableNavigableSet<>(
1299 ns.tailSet(fromElement, inclusive));
1300 }
1301 }
1302
1303 /**
1304 * Returns an unmodifiable view of the specified list. This method allows
1305 * modules to provide users with "read-only" access to internal
1306 * lists. Query operations on the returned list "read through" to the
1307 * specified list, and attempts to modify the returned list, whether
1308 * direct or via its iterator, result in an
1309 * <tt>UnsupportedOperationException</tt>.<p>
1310 *
1311 * The returned list will be serializable if the specified list
1312 * is serializable. Similarly, the returned list will implement
1313 * {@link RandomAccess} if the specified list does.
1314 *
1315 * @param list the list for which an unmodifiable view is to be returned.
1316 * @return an unmodifiable view of the specified list.
1317 */
1318 public static <T> List<T> unmodifiableList(List<? extends T> list) {
1319 return (list instanceof RandomAccess ?
1320 new UnmodifiableRandomAccessList<>(list) :
1321 new UnmodifiableList<>(list));
1322 }
1323
1324 /**
1325 * @serial include
1326 */
1327 static class UnmodifiableList<E> extends UnmodifiableCollection<E>
1328 implements List<E> {
1329 private static final long serialVersionUID = -283967356065247728L;
1330
1331 final List<? extends E> list;
1332
1333 UnmodifiableList(List<? extends E> list) {
1334 super(list);
1335 this.list = list;
1336 }
1337
1338 public boolean equals(Object o) {return o == this || list.equals(o);}
1339 public int hashCode() {return list.hashCode();}
1340
1341 public E get(int index) {return list.get(index);}
1342 public E set(int index, E element) {
1343 throw new UnsupportedOperationException();
1344 }
1345 public void add(int index, E element) {
1346 throw new UnsupportedOperationException();
1347 }
1348 public E remove(int index) {
1349 throw new UnsupportedOperationException();
1350 }
1351 public int indexOf(Object o) {return list.indexOf(o);}
1352 public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
1353 public boolean addAll(int index, Collection<? extends E> c) {
1354 throw new UnsupportedOperationException();
1355 }
1356
1357 @Override
1358 public void replaceAll(UnaryOperator<E> operator) {
1359 throw new UnsupportedOperationException();
1360 }
1361 @Override
1362 public void sort(Comparator<? super E> c) {
1363 throw new UnsupportedOperationException();
1364 }
1365
1366 public ListIterator<E> listIterator() {return listIterator(0);}
1367
1368 public ListIterator<E> listIterator(final int index) {
1369 return new ListIterator<E>() {
1370 private final ListIterator<? extends E> i
1371 = list.listIterator(index);
1372
1373 public boolean hasNext() {return i.hasNext();}
1374 public E next() {return i.next();}
1375 public boolean hasPrevious() {return i.hasPrevious();}
1376 public E previous() {return i.previous();}
1377 public int nextIndex() {return i.nextIndex();}
1378 public int previousIndex() {return i.previousIndex();}
1379
1380 public void remove() {
1381 throw new UnsupportedOperationException();
1382 }
1383 public void set(E e) {
1384 throw new UnsupportedOperationException();
1385 }
1386 public void add(E e) {
1387 throw new UnsupportedOperationException();
1388 }
1389
1390 @Override
1391 public void forEachRemaining(Consumer<? super E> action) {
1392 i.forEachRemaining(action);
1393 }
1394 };
1395 }
1396
1397 public List<E> subList(int fromIndex, int toIndex) {
1398 return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
1399 }
1400
1401 /**
1402 * UnmodifiableRandomAccessList instances are serialized as
1403 * UnmodifiableList instances to allow them to be deserialized
1404 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
1405 * This method inverts the transformation. As a beneficial
1406 * side-effect, it also grafts the RandomAccess marker onto
1407 * UnmodifiableList instances that were serialized in pre-1.4 JREs.
1408 *
1409 * Note: Unfortunately, UnmodifiableRandomAccessList instances
1410 * serialized in 1.4.1 and deserialized in 1.4 will become
1411 * UnmodifiableList instances, as this method was missing in 1.4.
1412 */
1413 private Object readResolve() {
1414 return (list instanceof RandomAccess
1415 ? new UnmodifiableRandomAccessList<>(list)
1416 : this);
1417 }
1418 }
1419
1420 /**
1421 * @serial include
1422 */
1423 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
1424 implements RandomAccess
1425 {
1426 UnmodifiableRandomAccessList(List<? extends E> list) {
1427 super(list);
1428 }
1429
1430 public List<E> subList(int fromIndex, int toIndex) {
1431 return new UnmodifiableRandomAccessList<>(
1432 list.subList(fromIndex, toIndex));
1433 }
1434
1435 private static final long serialVersionUID = -2542308836966382001L;
1436
1437 /**
1438 * Allows instances to be deserialized in pre-1.4 JREs (which do
1439 * not have UnmodifiableRandomAccessList). UnmodifiableList has
1440 * a readResolve method that inverts this transformation upon
1441 * deserialization.
1442 */
1443 private Object writeReplace() {
1444 return new UnmodifiableList<>(list);
1445 }
1446 }
1447
1448 /**
1449 * Returns an unmodifiable view of the specified map. This method
1450 * allows modules to provide users with "read-only" access to internal
1451 * maps. Query operations on the returned map "read through"
1452 * to the specified map, and attempts to modify the returned
1453 * map, whether direct or via its collection views, result in an
1454 * <tt>UnsupportedOperationException</tt>.<p>
1455 *
1456 * The returned map will be serializable if the specified map
1457 * is serializable.
1458 *
1459 * @param m the map for which an unmodifiable view is to be returned.
1460 * @return an unmodifiable view of the specified map.
1461 */
1462 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
1463 return new UnmodifiableMap<>(m);
1464 }
1465
1466 /**
1467 * @serial include
1468 */
1469 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
1470 private static final long serialVersionUID = -1034234728574286014L;
1471
1472 private final Map<? extends K, ? extends V> m;
1473
1474 UnmodifiableMap(Map<? extends K, ? extends V> m) {
1475 if (m==null)
1476 throw new NullPointerException();
1477 this.m = m;
1478 }
1479
1480 public int size() {return m.size();}
1481 public boolean isEmpty() {return m.isEmpty();}
1482 public boolean containsKey(Object key) {return m.containsKey(key);}
1483 public boolean containsValue(Object val) {return m.containsValue(val);}
1484 public V get(Object key) {return m.get(key);}
1485
1486 public V put(K key, V value) {
1487 throw new UnsupportedOperationException();
1488 }
1489 public V remove(Object key) {
1490 throw new UnsupportedOperationException();
1491 }
1492 public void putAll(Map<? extends K, ? extends V> m) {
1493 throw new UnsupportedOperationException();
1494 }
1495 public void clear() {
1496 throw new UnsupportedOperationException();
1497 }
1498
1499 private transient Set<K> keySet = null;
1500 private transient Set<Map.Entry<K,V>> entrySet = null;
1501 private transient Collection<V> values = null;
1502
1503 public Set<K> keySet() {
1504 if (keySet==null)
1505 keySet = unmodifiableSet(m.keySet());
1506 return keySet;
1507 }
1508
1509 public Set<Map.Entry<K,V>> entrySet() {
1510 if (entrySet==null)
1511 entrySet = new UnmodifiableEntrySet<>(m.entrySet());
1512 return entrySet;
1513 }
1514
1515 public Collection<V> values() {
1516 if (values==null)
1517 values = unmodifiableCollection(m.values());
1518 return values;
1519 }
1520
1521 public boolean equals(Object o) {return o == this || m.equals(o);}
1522 public int hashCode() {return m.hashCode();}
1523 public String toString() {return m.toString();}
1524
1525 // Override default methods in Map
1526 @Override
1527 @SuppressWarnings("unchecked")
1528 public V getOrDefault(Object k, V defaultValue) {
1529 // Safe cast as we don't change the value
1530 return ((Map<K, V>)m).getOrDefault(k, defaultValue);
1531 }
1532
1533 @Override
1534 public void forEach(BiConsumer<? super K, ? super V> action) {
1535 m.forEach(action);
1536 }
1537
1538 @Override
1539 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1540 throw new UnsupportedOperationException();
1541 }
1542
1543 @Override
1544 public V putIfAbsent(K key, V value) {
1545 throw new UnsupportedOperationException();
1546 }
1547
1548 @Override
1549 public boolean remove(Object key, Object value) {
1550 throw new UnsupportedOperationException();
1551 }
1552
1553 @Override
1554 public boolean replace(K key, V oldValue, V newValue) {
1555 throw new UnsupportedOperationException();
1556 }
1557
1558 @Override
1559 public V replace(K key, V value) {
1560 throw new UnsupportedOperationException();
1561 }
1562
1563 @Override
1564 public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
1565 throw new UnsupportedOperationException();
1566 }
1567
1568 @Override
1569 public V computeIfPresent(K key,
1570 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1571 throw new UnsupportedOperationException();
1572 }
1573
1574 @Override
1575 public V compute(K key,
1576 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1577 throw new UnsupportedOperationException();
1578 }
1579
1580 @Override
1581 public V merge(K key, V value,
1582 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1583 throw new UnsupportedOperationException();
1584 }
1585
1586 /**
1587 * We need this class in addition to UnmodifiableSet as
1588 * Map.Entries themselves permit modification of the backing Map
1589 * via their setValue operation. This class is subtle: there are
1590 * many possible attacks that must be thwarted.
1591 *
1592 * @serial include
1593 */
1594 static class UnmodifiableEntrySet<K,V>
1595 extends UnmodifiableSet<Map.Entry<K,V>> {
1596 private static final long serialVersionUID = 7854390611657943733L;
1597
1598 @SuppressWarnings({"unchecked", "rawtypes"})
1599 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
1600 // Need to cast to raw in order to work around a limitation in the type system
1601 super((Set)s);
1602 }
1603 public Iterator<Map.Entry<K,V>> iterator() {
1604 return new Iterator<Map.Entry<K,V>>() {
1605 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
1606
1607 public boolean hasNext() {
1608 return i.hasNext();
1609 }
1610 public Map.Entry<K,V> next() {
1611 return new UnmodifiableEntry<>(i.next());
1612 }
1613 public void remove() {
1614 throw new UnsupportedOperationException();
1615 }
1616 };
1617 }
1618
1619 @SuppressWarnings("unchecked")
1620 public Object[] toArray() {
1621 Object[] a = c.toArray();
1622 for (int i=0; i<a.length; i++)
1623 a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]);
1624 return a;
1625 }
1626
1627 @SuppressWarnings("unchecked")
1628 public <T> T[] toArray(T[] a) {
1629 // We don't pass a to c.toArray, to avoid window of
1630 // vulnerability wherein an unscrupulous multithreaded client
1631 // could get his hands on raw (unwrapped) Entries from c.
1632 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
1633
1634 for (int i=0; i<arr.length; i++)
1635 arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]);
1636
1637 if (arr.length > a.length)
1638 return (T[])arr;
1639
1640 System.arraycopy(arr, 0, a, 0, arr.length);
1641 if (a.length > arr.length)
1642 a[arr.length] = null;
1643 return a;
1644 }
1645
1646 /**
1647 * This method is overridden to protect the backing set against
1648 * an object with a nefarious equals function that senses
1649 * that the equality-candidate is Map.Entry and calls its
1650 * setValue method.
1651 */
1652 public boolean contains(Object o) {
1653 if (!(o instanceof Map.Entry))
1654 return false;
1655 return c.contains(
1656 new UnmodifiableEntry<>((Map.Entry<?,?>) o));
1657 }
1658
1659 /**
1660 * The next two methods are overridden to protect against
1661 * an unscrupulous List whose contains(Object o) method senses
1662 * when o is a Map.Entry, and calls o.setValue.
1663 */
1664 public boolean containsAll(Collection<?> coll) {
1665 for (Object e : coll) {
1666 if (!contains(e)) // Invokes safe contains() above
1667 return false;
1668 }
1669 return true;
1670 }
1671 public boolean equals(Object o) {
1672 if (o == this)
1673 return true;
1674
1675 if (!(o instanceof Set))
1676 return false;
1677 Set<?> s = (Set<?>) o;
1678 if (s.size() != c.size())
1679 return false;
1680 return containsAll(s); // Invokes safe containsAll() above
1681 }
1682
1683 /**
1684 * This "wrapper class" serves two purposes: it prevents
1685 * the client from modifying the backing Map, by short-circuiting
1686 * the setValue method, and it protects the backing Map against
1687 * an ill-behaved Map.Entry that attempts to modify another
1688 * Map Entry when asked to perform an equality check.
1689 */
1690 private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
1691 private Map.Entry<? extends K, ? extends V> e;
1692
1693 UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e)
1694 {this.e = Objects.requireNonNull(e);}
1695
1696 public K getKey() {return e.getKey();}
1697 public V getValue() {return e.getValue();}
1698 public V setValue(V value) {
1699 throw new UnsupportedOperationException();
1700 }
1701 public int hashCode() {return e.hashCode();}
1702 public boolean equals(Object o) {
1703 if (this == o)
1704 return true;
1705 if (!(o instanceof Map.Entry))
1706 return false;
1707 Map.Entry<?,?> t = (Map.Entry<?,?>)o;
1708 return eq(e.getKey(), t.getKey()) &&
1709 eq(e.getValue(), t.getValue());
1710 }
1711 public String toString() {return e.toString();}
1712 }
1713 }
1714 }
1715
1716 /**
1717 * Returns an unmodifiable view of the specified sorted map. This method
1718 * allows modules to provide users with "read-only" access to internal
1719 * sorted maps. Query operations on the returned sorted map "read through"
1720 * to the specified sorted map. Attempts to modify the returned
1721 * sorted map, whether direct, via its collection views, or via its
1722 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in
1723 * an <tt>UnsupportedOperationException</tt>.<p>
1724 *
1725 * The returned sorted map will be serializable if the specified sorted map
1726 * is serializable.
1727 *
1728 * @param m the sorted map for which an unmodifiable view is to be
1729 * returned.
1730 * @return an unmodifiable view of the specified sorted map.
1731 */
1732 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
1733 return new UnmodifiableSortedMap<>(m);
1734 }
1735
1736 /**
1737 * @serial include
1738 */
1739 static class UnmodifiableSortedMap<K,V>
1740 extends UnmodifiableMap<K,V>
1741 implements SortedMap<K,V>, Serializable {
1742 private static final long serialVersionUID = -8806743815996713206L;
1743
1744 private final SortedMap<K, ? extends V> sm;
1745
1746 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; }
1747 public Comparator<? super K> comparator() { return sm.comparator(); }
1748 public SortedMap<K,V> subMap(K fromKey, K toKey)
1749 { return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); }
1750 public SortedMap<K,V> headMap(K toKey)
1751 { return new UnmodifiableSortedMap<>(sm.headMap(toKey)); }
1752 public SortedMap<K,V> tailMap(K fromKey)
1753 { return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); }
1754 public K firstKey() { return sm.firstKey(); }
1755 public K lastKey() { return sm.lastKey(); }
1756 }
1757
1758 /**
1759 * Returns an unmodifiable view of the specified navigable map. This method
1760 * allows modules to provide users with "read-only" access to internal
1761 * navigable maps. Query operations on the returned navigable map "read
1762 * through" to the specified navigable map. Attempts to modify the returned
1763 * navigable map, whether direct, via its collection views, or via its
1764 * {@code subMap}, {@code headMap}, or {@code tailMap} views, result in
1765 * an {@code UnsupportedOperationException}.<p>
1766 *
1767 * The returned navigable map will be serializable if the specified
1768 * navigable map is serializable.
1769 *
1770 * @param m the navigable map for which an unmodifiable view is to be
1771 * returned
1772 * @return an unmodifiable view of the specified navigable map
1773 * @since 1.8
1774 */
1775 public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {
1776 return new UnmodifiableNavigableMap<>(m);
1777 }
1778
1779 /**
1780 * @serial include
1781 */
1782 static class UnmodifiableNavigableMap<K,V>
1783 extends UnmodifiableSortedMap<K,V>
1784 implements NavigableMap<K,V>, Serializable {
1785 private static final long serialVersionUID = -4858195264774772197L;
1786
1787 /**
1788 * A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve
1789 * to preserve singleton property.
1790 *
1791 * @param <K> type of keys, if there were any, and of bounds
1792 * @param <V> type of values, if there were any
1793 */
1794 private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V>
1795 implements Serializable {
1796
1797 private static final long serialVersionUID = -2239321462712562324L;
1798
1799 EmptyNavigableMap() { super(new TreeMap()); }
1800
1801 @Override
1802 public NavigableSet<K> navigableKeySet()
1803 { return emptyNavigableSet(); }
1804
1805 private Object readResolve() { return EMPTY_NAVIGABLE_MAP; }
1806 }
1807
1808 /**
1809 * Singleton for {@link emptyNavigableMap()} which is also immutable.
1810 */
1811 private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP =
1812 new EmptyNavigableMap<>();
1813
1814 /**
1815 * The instance we wrap and protect.
1816 */
1817 private final NavigableMap<K, ? extends V> nm;
1818
1819 UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m)
1820 {super(m); nm = m;}
1821
1822 public K lowerKey(K key) { return nm.lowerKey(key); }
1823 public K floorKey(K key) { return nm.floorKey(key); }
1824 public K ceilingKey(K key) { return nm.ceilingKey(key); }
1825 public K higherKey(K key) { return nm.higherKey(key); }
1826
1827 public Entry<K, V> lowerEntry(K key) {
1828 Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key);
1829 return (null != lower)
1830 ? new UnmodifiableEntrySet.UnmodifiableEntry(lower)
1831 : null;
1832 }
1833
1834 public Entry<K, V> floorEntry(K key) {
1835 Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key);
1836 return (null != floor)
1837 ? new UnmodifiableEntrySet.UnmodifiableEntry(floor)
1838 : null;
1839 }
1840
1841 public Entry<K, V> ceilingEntry(K key) {
1842 Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key);
1843 return (null != ceiling)
1844 ? new UnmodifiableEntrySet.UnmodifiableEntry(ceiling)
1845 : null;
1846 }
1847
1848
1849 public Entry<K, V> higherEntry(K key) {
1850 Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key);
1851 return (null != higher)
1852 ? new UnmodifiableEntrySet.UnmodifiableEntry(higher)
1853 : null;
1854 }
1855
1856 public Entry<K, V> firstEntry() {
1857 Entry<K,V> first = (Entry<K, V>) nm.firstEntry();
1858 return (null != first)
1859 ? new UnmodifiableEntrySet.UnmodifiableEntry(first)
1860 : null;
1861 }
1862
1863 public Entry<K, V> lastEntry() {
1864 Entry<K,V> last = (Entry<K, V>) nm.lastEntry();
1865 return (null != last)
1866 ? new UnmodifiableEntrySet.UnmodifiableEntry(last)
1867 : null;
1868 }
1869
1870 public Entry<K, V> pollFirstEntry()
1871 { throw new UnsupportedOperationException(); }
1872 public Entry<K, V> pollLastEntry()
1873 { throw new UnsupportedOperationException(); }
1874 public NavigableMap<K, V> descendingMap()
1875 { return unmodifiableNavigableMap(nm.descendingMap()); }
1876 public NavigableSet<K> navigableKeySet()
1877 { return unmodifiableNavigableSet(nm.navigableKeySet()); }
1878 public NavigableSet<K> descendingKeySet()
1879 { return unmodifiableNavigableSet(nm.descendingKeySet()); }
1880
1881 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
1882 return unmodifiableNavigableMap(
1883 nm.subMap(fromKey, fromInclusive, toKey, toInclusive));
1884 }
1885
1886 public NavigableMap<K, V> headMap(K toKey, boolean inclusive)
1887 { return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); }
1888 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive)
1889 { return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); }
1890 }
1891
1892 // Synch Wrappers
1893
1894 /**
1895 * Returns a synchronized (thread-safe) collection backed by the specified
1896 * collection. In order to guarantee serial access, it is critical that
1897 * <strong>all</strong> access to the backing collection is accomplished
1898 * through the returned collection.<p>
1899 *
1900 * It is imperative that the user manually synchronize on the returned
1901 * collection when traversing it via {@link Iterator} or
1902 * {@link Spliterator}:
1903 * <pre>
1904 * Collection c = Collections.synchronizedCollection(myCollection);
1905 * ...
1906 * synchronized (c) {
1907 * Iterator i = c.iterator(); // Must be in the synchronized block
1908 * while (i.hasNext())
1909 * foo(i.next());
1910 * }
1911 * </pre>
1912 * Failure to follow this advice may result in non-deterministic behavior.
1913 *
1914 * <p>The returned collection does <i>not</i> pass the {@code hashCode}
1915 * and {@code equals} operations through to the backing collection, but
1916 * relies on {@code Object}'s equals and hashCode methods. This is
1917 * necessary to preserve the contracts of these operations in the case
1918 * that the backing collection is a set or a list.<p>
1919 *
1920 * The returned collection will be serializable if the specified collection
1921 * is serializable.
1922 *
1923 * @param c the collection to be "wrapped" in a synchronized collection.
1924 * @return a synchronized view of the specified collection.
1925 */
1926 public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
1927 return new SynchronizedCollection<>(c);
1928 }
1929
1930 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
1931 return new SynchronizedCollection<>(c, mutex);
1932 }
1933
1934 /**
1935 * @serial include
1936 */
1937 static class SynchronizedCollection<E> implements Collection<E>, Serializable {
1938 private static final long serialVersionUID = 3053995032091335093L;
1939
1940 final Collection<E> c; // Backing Collection
1941 final Object mutex; // Object on which to synchronize
1942
1943 SynchronizedCollection(Collection<E> c) {
1944 this.c = Objects.requireNonNull(c);
1945 mutex = this;
1946 }
1947
1948 SynchronizedCollection(Collection<E> c, Object mutex) {
1949 this.c = Objects.requireNonNull(c);
1950 this.mutex = Objects.requireNonNull(mutex);
1951 }
1952
1953 public int size() {
1954 synchronized (mutex) {return c.size();}
1955 }
1956 public boolean isEmpty() {
1957 synchronized (mutex) {return c.isEmpty();}
1958 }
1959 public boolean contains(Object o) {
1960 synchronized (mutex) {return c.contains(o);}
1961 }
1962 public Object[] toArray() {
1963 synchronized (mutex) {return c.toArray();}
1964 }
1965 public <T> T[] toArray(T[] a) {
1966 synchronized (mutex) {return c.toArray(a);}
1967 }
1968
1969 public Iterator<E> iterator() {
1970 return c.iterator(); // Must be manually synched by user!
1971 }
1972
1973 public boolean add(E e) {
1974 synchronized (mutex) {return c.add(e);}
1975 }
1976 public boolean remove(Object o) {
1977 synchronized (mutex) {return c.remove(o);}
1978 }
1979
1980 public boolean containsAll(Collection<?> coll) {
1981 synchronized (mutex) {return c.containsAll(coll);}
1982 }
1983 public boolean addAll(Collection<? extends E> coll) {
1984 synchronized (mutex) {return c.addAll(coll);}
1985 }
1986 public boolean removeAll(Collection<?> coll) {
1987 synchronized (mutex) {return c.removeAll(coll);}
1988 }
1989 public boolean retainAll(Collection<?> coll) {
1990 synchronized (mutex) {return c.retainAll(coll);}
1991 }
1992 public void clear() {
1993 synchronized (mutex) {c.clear();}
1994 }
1995 public String toString() {
1996 synchronized (mutex) {return c.toString();}
1997 }
1998 // Override default methods in Collection
1999 @Override
2000 public void forEach(Consumer<? super E> consumer) {
2001 synchronized (mutex) {c.forEach(consumer);}
2002 }
2003 @Override
2004 public boolean removeIf(Predicate<? super E> filter) {
2005 synchronized (mutex) {return c.removeIf(filter);}
2006 }
2007 @Override
2008 public Spliterator<E> spliterator() {
2009 return c.spliterator(); // Must be manually synched by user!
2010 }
2011 private void writeObject(ObjectOutputStream s) throws IOException {
2012 synchronized (mutex) {s.defaultWriteObject();}
2013 }
2014 }
2015
2016 /**
2017 * Returns a synchronized (thread-safe) set backed by the specified
2018 * set. In order to guarantee serial access, it is critical that
2019 * <strong>all</strong> access to the backing set is accomplished
2020 * through the returned set.<p>
2021 *
2022 * It is imperative that the user manually synchronize on the returned
2023 * set when iterating over it:
2024 * <pre>
2025 * Set s = Collections.synchronizedSet(new HashSet());
2026 * ...
2027 * synchronized (s) {
2028 * Iterator i = s.iterator(); // Must be in the synchronized block
2029 * while (i.hasNext())
2030 * foo(i.next());
2031 * }
2032 * </pre>
2033 * Failure to follow this advice may result in non-deterministic behavior.
2034 *
2035 * <p>The returned set will be serializable if the specified set is
2036 * serializable.
2037 *
2038 * @param s the set to be "wrapped" in a synchronized set.
2039 * @return a synchronized view of the specified set.
2040 */
2041 public static <T> Set<T> synchronizedSet(Set<T> s) {
2042 return new SynchronizedSet<>(s);
2043 }
2044
2045 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
2046 return new SynchronizedSet<>(s, mutex);
2047 }
2048
2049 /**
2050 * @serial include
2051 */
2052 static class SynchronizedSet<E>
2053 extends SynchronizedCollection<E>
2054 implements Set<E> {
2055 private static final long serialVersionUID = 487447009682186044L;
2056
2057 SynchronizedSet(Set<E> s) {
2058 super(s);
2059 }
2060 SynchronizedSet(Set<E> s, Object mutex) {
2061 super(s, mutex);
2062 }
2063
2064 public boolean equals(Object o) {
2065 if (this == o)
2066 return true;
2067 synchronized (mutex) {return c.equals(o);}
2068 }
2069 public int hashCode() {
2070 synchronized (mutex) {return c.hashCode();}
2071 }
2072 }
2073
2074 /**
2075 * Returns a synchronized (thread-safe) sorted set backed by the specified
2076 * sorted set. In order to guarantee serial access, it is critical that
2077 * <strong>all</strong> access to the backing sorted set is accomplished
2078 * through the returned sorted set (or its views).<p>
2079 *
2080 * It is imperative that the user manually synchronize on the returned
2081 * sorted set when iterating over it or any of its <tt>subSet</tt>,
2082 * <tt>headSet</tt>, or <tt>tailSet</tt> views.
2083 * <pre>
2084 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2085 * ...
2086 * synchronized (s) {
2087 * Iterator i = s.iterator(); // Must be in the synchronized block
2088 * while (i.hasNext())
2089 * foo(i.next());
2090 * }
2091 * </pre>
2092 * or:
2093 * <pre>
2094 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2095 * SortedSet s2 = s.headSet(foo);
2096 * ...
2097 * synchronized (s) { // Note: s, not s2!!!
2098 * Iterator i = s2.iterator(); // Must be in the synchronized block
2099 * while (i.hasNext())
2100 * foo(i.next());
2101 * }
2102 * </pre>
2103 * Failure to follow this advice may result in non-deterministic behavior.
2104 *
2105 * <p>The returned sorted set will be serializable if the specified
2106 * sorted set is serializable.
2107 *
2108 * @param s the sorted set to be "wrapped" in a synchronized sorted set.
2109 * @return a synchronized view of the specified sorted set.
2110 */
2111 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
2112 return new SynchronizedSortedSet<>(s);
2113 }
2114
2115 /**
2116 * @serial include
2117 */
2118 static class SynchronizedSortedSet<E>
2119 extends SynchronizedSet<E>
2120 implements SortedSet<E>
2121 {
2122 private static final long serialVersionUID = 8695801310862127406L;
2123
2124 private final SortedSet<E> ss;
2125
2126 SynchronizedSortedSet(SortedSet<E> s) {
2127 super(s);
2128 ss = s;
2129 }
2130 SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
2131 super(s, mutex);
2132 ss = s;
2133 }
2134
2135 public Comparator<? super E> comparator() {
2136 synchronized (mutex) {return ss.comparator();}
2137 }
2138
2139 public SortedSet<E> subSet(E fromElement, E toElement) {
2140 synchronized (mutex) {
2141 return new SynchronizedSortedSet<>(
2142 ss.subSet(fromElement, toElement), mutex);
2143 }
2144 }
2145 public SortedSet<E> headSet(E toElement) {
2146 synchronized (mutex) {
2147 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
2148 }
2149 }
2150 public SortedSet<E> tailSet(E fromElement) {
2151 synchronized (mutex) {
2152 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
2153 }
2154 }
2155
2156 public E first() {
2157 synchronized (mutex) {return ss.first();}
2158 }
2159 public E last() {
2160 synchronized (mutex) {return ss.last();}
2161 }
2162 }
2163
2164 /**
2165 * Returns a synchronized (thread-safe) navigable set backed by the
2166 * specified navigable set. In order to guarantee serial access, it is
2167 * critical that <strong>all</strong> access to the backing navigable set is
2168 * accomplished through the returned navigable set (or its views).<p>
2169 *
2170 * It is imperative that the user manually synchronize on the returned
2171 * navigable set when iterating over it or any of its {@code subSet},
2172 * {@code headSet}, or {@code tailSet} views.
2173 * <pre>
2174 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
2175 * ...
2176 * synchronized (s) {
2177 * Iterator i = s.iterator(); // Must be in the synchronized block
2178 * while (i.hasNext())
2179 * foo(i.next());
2180 * }
2181 * </pre>
2182 * or:
2183 * <pre>
2184 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
2185 * NavigableSet s2 = s.headSet(foo, true);
2186 * ...
2187 * synchronized (s) { // Note: s, not s2!!!
2188 * Iterator i = s2.iterator(); // Must be in the synchronized block
2189 * while (i.hasNext())
2190 * foo(i.next());
2191 * }
2192 * </pre>
2193 * Failure to follow this advice may result in non-deterministic behavior.
2194 *
2195 * <p>The returned navigable set will be serializable if the specified
2196 * navigable set is serializable.
2197 *
2198 * @param s the navigable set to be "wrapped" in a synchronized navigable
2199 * set
2200 * @return a synchronized view of the specified navigable set
2201 * @since 1.8
2202 */
2203 public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) {
2204 return new SynchronizedNavigableSet<>(s);
2205 }
2206
2207 /**
2208 * @serial include
2209 */
2210 static class SynchronizedNavigableSet<E>
2211 extends SynchronizedSortedSet<E>
2212 implements NavigableSet<E>
2213 {
2214 private static final long serialVersionUID = -5505529816273629798L;
2215
2216 private final NavigableSet<E> ns;
2217
2218 SynchronizedNavigableSet(NavigableSet<E> s) {
2219 super(s);
2220 ns = s;
2221 }
2222
2223 SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) {
2224 super(s, mutex);
2225 ns = s;
2226 }
2227 public E lower(E e) { synchronized (mutex) {return ns.lower(e);} }
2228 public E floor(E e) { synchronized (mutex) {return ns.floor(e);} }
2229 public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} }
2230 public E higher(E e) { synchronized (mutex) {return ns.higher(e);} }
2231 public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} }
2232 public E pollLast() { synchronized (mutex) {return ns.pollLast();} }
2233
2234 public NavigableSet<E> descendingSet() {
2235 synchronized (mutex) {
2236 return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex);
2237 }
2238 }
2239
2240 public Iterator<E> descendingIterator()
2241 { synchronized (mutex) { return descendingSet().iterator(); } }
2242
2243 public NavigableSet<E> subSet(E fromElement, E toElement) {
2244 synchronized (mutex) {
2245 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex);
2246 }
2247 }
2248 public NavigableSet<E> headSet(E toElement) {
2249 synchronized (mutex) {
2250 return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex);
2251 }
2252 }
2253 public NavigableSet<E> tailSet(E fromElement) {
2254 synchronized (mutex) {
2255 return new SynchronizedNavigableSet(ns.tailSet(fromElement, true), mutex);
2256 }
2257 }
2258
2259 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
2260 synchronized (mutex) {
2261 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex);
2262 }
2263 }
2264
2265 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
2266 synchronized (mutex) {
2267 return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex);
2268 }
2269 }
2270
2271 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
2272 synchronized (mutex) {
2273 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive));
2274 }
2275 }
2276 }
2277
2278 /**
2279 * Returns a synchronized (thread-safe) list backed by the specified
2280 * list. In order to guarantee serial access, it is critical that
2281 * <strong>all</strong> access to the backing list is accomplished
2282 * through the returned list.<p>
2283 *
2284 * It is imperative that the user manually synchronize on the returned
2285 * list when iterating over it:
2286 * <pre>
2287 * List list = Collections.synchronizedList(new ArrayList());
2288 * ...
2289 * synchronized (list) {
2290 * Iterator i = list.iterator(); // Must be in synchronized block
2291 * while (i.hasNext())
2292 * foo(i.next());
2293 * }
2294 * </pre>
2295 * Failure to follow this advice may result in non-deterministic behavior.
2296 *
2297 * <p>The returned list will be serializable if the specified list is
2298 * serializable.
2299 *
2300 * @param list the list to be "wrapped" in a synchronized list.
2301 * @return a synchronized view of the specified list.
2302 */
2303 public static <T> List<T> synchronizedList(List<T> list) {
2304 return (list instanceof RandomAccess ?
2305 new SynchronizedRandomAccessList<>(list) :
2306 new SynchronizedList<>(list));
2307 }
2308
2309 static <T> List<T> synchronizedList(List<T> list, Object mutex) {
2310 return (list instanceof RandomAccess ?
2311 new SynchronizedRandomAccessList<>(list, mutex) :
2312 new SynchronizedList<>(list, mutex));
2313 }
2314
2315 /**
2316 * @serial include
2317 */
2318 static class SynchronizedList<E>
2319 extends SynchronizedCollection<E>
2320 implements List<E> {
2321 private static final long serialVersionUID = -7754090372962971524L;
2322
2323 final List<E> list;
2324
2325 SynchronizedList(List<E> list) {
2326 super(list);
2327 this.list = list;
2328 }
2329 SynchronizedList(List<E> list, Object mutex) {
2330 super(list, mutex);
2331 this.list = list;
2332 }
2333
2334 public boolean equals(Object o) {
2335 if (this == o)
2336 return true;
2337 synchronized (mutex) {return list.equals(o);}
2338 }
2339 public int hashCode() {
2340 synchronized (mutex) {return list.hashCode();}
2341 }
2342
2343 public E get(int index) {
2344 synchronized (mutex) {return list.get(index);}
2345 }
2346 public E set(int index, E element) {
2347 synchronized (mutex) {return list.set(index, element);}
2348 }
2349 public void add(int index, E element) {
2350 synchronized (mutex) {list.add(index, element);}
2351 }
2352 public E remove(int index) {
2353 synchronized (mutex) {return list.remove(index);}
2354 }
2355
2356 public int indexOf(Object o) {
2357 synchronized (mutex) {return list.indexOf(o);}
2358 }
2359 public int lastIndexOf(Object o) {
2360 synchronized (mutex) {return list.lastIndexOf(o);}
2361 }
2362
2363 public boolean addAll(int index, Collection<? extends E> c) {
2364 synchronized (mutex) {return list.addAll(index, c);}
2365 }
2366
2367 public ListIterator<E> listIterator() {
2368 return list.listIterator(); // Must be manually synched by user
2369 }
2370
2371 public ListIterator<E> listIterator(int index) {
2372 return list.listIterator(index); // Must be manually synched by user
2373 }
2374
2375 public List<E> subList(int fromIndex, int toIndex) {
2376 synchronized (mutex) {
2377 return new SynchronizedList<>(list.subList(fromIndex, toIndex),
2378 mutex);
2379 }
2380 }
2381
2382 @Override
2383 public void replaceAll(UnaryOperator<E> operator) {
2384 synchronized (mutex) {list.replaceAll(operator);}
2385 }
2386 @Override
2387 public void sort(Comparator<? super E> c) {
2388 synchronized (mutex) {list.sort(c);}
2389 }
2390
2391 /**
2392 * SynchronizedRandomAccessList instances are serialized as
2393 * SynchronizedList instances to allow them to be deserialized
2394 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
2395 * This method inverts the transformation. As a beneficial
2396 * side-effect, it also grafts the RandomAccess marker onto
2397 * SynchronizedList instances that were serialized in pre-1.4 JREs.
2398 *
2399 * Note: Unfortunately, SynchronizedRandomAccessList instances
2400 * serialized in 1.4.1 and deserialized in 1.4 will become
2401 * SynchronizedList instances, as this method was missing in 1.4.
2402 */
2403 private Object readResolve() {
2404 return (list instanceof RandomAccess
2405 ? new SynchronizedRandomAccessList<>(list)
2406 : this);
2407 }
2408 }
2409
2410 /**
2411 * @serial include
2412 */
2413 static class SynchronizedRandomAccessList<E>
2414 extends SynchronizedList<E>
2415 implements RandomAccess {
2416
2417 SynchronizedRandomAccessList(List<E> list) {
2418 super(list);
2419 }
2420
2421 SynchronizedRandomAccessList(List<E> list, Object mutex) {
2422 super(list, mutex);
2423 }
2424
2425 public List<E> subList(int fromIndex, int toIndex) {
2426 synchronized (mutex) {
2427 return new SynchronizedRandomAccessList<>(
2428 list.subList(fromIndex, toIndex), mutex);
2429 }
2430 }
2431
2432 private static final long serialVersionUID = 1530674583602358482L;
2433
2434 /**
2435 * Allows instances to be deserialized in pre-1.4 JREs (which do
2436 * not have SynchronizedRandomAccessList). SynchronizedList has
2437 * a readResolve method that inverts this transformation upon
2438 * deserialization.
2439 */
2440 private Object writeReplace() {
2441 return new SynchronizedList<>(list);
2442 }
2443 }
2444
2445 /**
2446 * Returns a synchronized (thread-safe) map backed by the specified
2447 * map. In order to guarantee serial access, it is critical that
2448 * <strong>all</strong> access to the backing map is accomplished
2449 * through the returned map.<p>
2450 *
2451 * It is imperative that the user manually synchronize on the returned
2452 * map when iterating over any of its collection views:
2453 * <pre>
2454 * Map m = Collections.synchronizedMap(new HashMap());
2455 * ...
2456 * Set s = m.keySet(); // Needn't be in synchronized block
2457 * ...
2458 * synchronized (m) { // Synchronizing on m, not s!
2459 * Iterator i = s.iterator(); // Must be in synchronized block
2460 * while (i.hasNext())
2461 * foo(i.next());
2462 * }
2463 * </pre>
2464 * Failure to follow this advice may result in non-deterministic behavior.
2465 *
2466 * <p>The returned map will be serializable if the specified map is
2467 * serializable.
2468 *
2469 * @param m the map to be "wrapped" in a synchronized map.
2470 * @return a synchronized view of the specified map.
2471 */
2472 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
2473 return new SynchronizedMap<>(m);
2474 }
2475
2476 /**
2477 * @serial include
2478 */
2479 private static class SynchronizedMap<K,V>
2480 implements Map<K,V>, Serializable {
2481 private static final long serialVersionUID = 1978198479659022715L;
2482
2483 private final Map<K,V> m; // Backing Map
2484 final Object mutex; // Object on which to synchronize
2485
2486 SynchronizedMap(Map<K,V> m) {
2487 this.m = Objects.requireNonNull(m);
2488 mutex = this;
2489 }
2490
2491 SynchronizedMap(Map<K,V> m, Object mutex) {
2492 this.m = m;
2493 this.mutex = mutex;
2494 }
2495
2496 public int size() {
2497 synchronized (mutex) {return m.size();}
2498 }
2499 public boolean isEmpty() {
2500 synchronized (mutex) {return m.isEmpty();}
2501 }
2502 public boolean containsKey(Object key) {
2503 synchronized (mutex) {return m.containsKey(key);}
2504 }
2505 public boolean containsValue(Object value) {
2506 synchronized (mutex) {return m.containsValue(value);}
2507 }
2508 public V get(Object key) {
2509 synchronized (mutex) {return m.get(key);}
2510 }
2511
2512 public V put(K key, V value) {
2513 synchronized (mutex) {return m.put(key, value);}
2514 }
2515 public V remove(Object key) {
2516 synchronized (mutex) {return m.remove(key);}
2517 }
2518 public void putAll(Map<? extends K, ? extends V> map) {
2519 synchronized (mutex) {m.putAll(map);}
2520 }
2521 public void clear() {
2522 synchronized (mutex) {m.clear();}
2523 }
2524
2525 private transient Set<K> keySet = null;
2526 private transient Set<Map.Entry<K,V>> entrySet = null;
2527 private transient Collection<V> values = null;
2528
2529 public Set<K> keySet() {
2530 synchronized (mutex) {
2531 if (keySet==null)
2532 keySet = new SynchronizedSet<>(m.keySet(), mutex);
2533 return keySet;
2534 }
2535 }
2536
2537 public Set<Map.Entry<K,V>> entrySet() {
2538 synchronized (mutex) {
2539 if (entrySet==null)
2540 entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
2541 return entrySet;
2542 }
2543 }
2544
2545 public Collection<V> values() {
2546 synchronized (mutex) {
2547 if (values==null)
2548 values = new SynchronizedCollection<>(m.values(), mutex);
2549 return values;
2550 }
2551 }
2552
2553 public boolean equals(Object o) {
2554 if (this == o)
2555 return true;
2556 synchronized (mutex) {return m.equals(o);}
2557 }
2558 public int hashCode() {
2559 synchronized (mutex) {return m.hashCode();}
2560 }
2561 public String toString() {
2562 synchronized (mutex) {return m.toString();}
2563 }
2564
2565 // Override default methods in Map
2566 @Override
2567 public V getOrDefault(Object k, V defaultValue) {
2568 synchronized (mutex) {return m.getOrDefault(k, defaultValue);}
2569 }
2570 @Override
2571 public void forEach(BiConsumer<? super K, ? super V> action) {
2572 synchronized (mutex) {m.forEach(action);}
2573 }
2574 @Override
2575 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
2576 synchronized (mutex) {m.replaceAll(function);}
2577 }
2578 @Override
2579 public V putIfAbsent(K key, V value) {
2580 synchronized (mutex) {return m.putIfAbsent(key, value);}
2581 }
2582 @Override
2583 public boolean remove(Object key, Object value) {
2584 synchronized (mutex) {return m.remove(key, value);}
2585 }
2586 @Override
2587 public boolean replace(K key, V oldValue, V newValue) {
2588 synchronized (mutex) {return m.replace(key, oldValue, newValue);}
2589 }
2590 @Override
2591 public V replace(K key, V value) {
2592 synchronized (mutex) {return m.replace(key, value);}
2593 }
2594 @Override
2595 public V computeIfAbsent(K key,
2596 Function<? super K, ? extends V> mappingFunction) {
2597 synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);}
2598 }
2599 @Override
2600 public V computeIfPresent(K key,
2601 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2602 synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);}
2603 }
2604 @Override
2605 public V compute(K key,
2606 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2607 synchronized (mutex) {return m.compute(key, remappingFunction);}
2608 }
2609 @Override
2610 public V merge(K key, V value,
2611 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
2612 synchronized (mutex) {return m.merge(key, value, remappingFunction);}
2613 }
2614
2615 private void writeObject(ObjectOutputStream s) throws IOException {
2616 synchronized (mutex) {s.defaultWriteObject();}
2617 }
2618 }
2619
2620 /**
2621 * Returns a synchronized (thread-safe) sorted map backed by the specified
2622 * sorted map. In order to guarantee serial access, it is critical that
2623 * <strong>all</strong> access to the backing sorted map is accomplished
2624 * through the returned sorted map (or its views).<p>
2625 *
2626 * It is imperative that the user manually synchronize on the returned
2627 * sorted map when iterating over any of its collection views, or the
2628 * collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or
2629 * <tt>tailMap</tt> views.
2630 * <pre>
2631 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2632 * ...
2633 * Set s = m.keySet(); // Needn't be in synchronized block
2634 * ...
2635 * synchronized (m) { // Synchronizing on m, not s!
2636 * Iterator i = s.iterator(); // Must be in synchronized block
2637 * while (i.hasNext())
2638 * foo(i.next());
2639 * }
2640 * </pre>
2641 * or:
2642 * <pre>
2643 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2644 * SortedMap m2 = m.subMap(foo, bar);
2645 * ...
2646 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2647 * ...
2648 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2649 * Iterator i = s.iterator(); // Must be in synchronized block
2650 * while (i.hasNext())
2651 * foo(i.next());
2652 * }
2653 * </pre>
2654 * Failure to follow this advice may result in non-deterministic behavior.
2655 *
2656 * <p>The returned sorted map will be serializable if the specified
2657 * sorted map is serializable.
2658 *
2659 * @param m the sorted map to be "wrapped" in a synchronized sorted map.
2660 * @return a synchronized view of the specified sorted map.
2661 */
2662 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
2663 return new SynchronizedSortedMap<>(m);
2664 }
2665
2666 /**
2667 * @serial include
2668 */
2669 static class SynchronizedSortedMap<K,V>
2670 extends SynchronizedMap<K,V>
2671 implements SortedMap<K,V>
2672 {
2673 private static final long serialVersionUID = -8798146769416483793L;
2674
2675 private final SortedMap<K,V> sm;
2676
2677 SynchronizedSortedMap(SortedMap<K,V> m) {
2678 super(m);
2679 sm = m;
2680 }
2681 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
2682 super(m, mutex);
2683 sm = m;
2684 }
2685
2686 public Comparator<? super K> comparator() {
2687 synchronized (mutex) {return sm.comparator();}
2688 }
2689
2690 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2691 synchronized (mutex) {
2692 return new SynchronizedSortedMap<>(
2693 sm.subMap(fromKey, toKey), mutex);
2694 }
2695 }
2696 public SortedMap<K,V> headMap(K toKey) {
2697 synchronized (mutex) {
2698 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
2699 }
2700 }
2701 public SortedMap<K,V> tailMap(K fromKey) {
2702 synchronized (mutex) {
2703 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
2704 }
2705 }
2706
2707 public K firstKey() {
2708 synchronized (mutex) {return sm.firstKey();}
2709 }
2710 public K lastKey() {
2711 synchronized (mutex) {return sm.lastKey();}
2712 }
2713 }
2714
2715 /**
2716 * Returns a synchronized (thread-safe) navigable map backed by the
2717 * specified navigable map. In order to guarantee serial access, it is
2718 * critical that <strong>all</strong> access to the backing navigable map is
2719 * accomplished through the returned navigable map (or its views).<p>
2720 *
2721 * It is imperative that the user manually synchronize on the returned
2722 * navigable map when iterating over any of its collection views, or the
2723 * collections views of any of its {@code subMap}, {@code headMap} or
2724 * {@code tailMap} views.
2725 * <pre>
2726 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
2727 * ...
2728 * Set s = m.keySet(); // Needn't be in synchronized block
2729 * ...
2730 * synchronized (m) { // Synchronizing on m, not s!
2731 * Iterator i = s.iterator(); // Must be in synchronized block
2732 * while (i.hasNext())
2733 * foo(i.next());
2734 * }
2735 * </pre>
2736 * or:
2737 * <pre>
2738 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
2739 * NavigableMap m2 = m.subMap(foo, true, bar, false);
2740 * ...
2741 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2742 * ...
2743 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2744 * Iterator i = s.iterator(); // Must be in synchronized block
2745 * while (i.hasNext())
2746 * foo(i.next());
2747 * }
2748 * </pre>
2749 * Failure to follow this advice may result in non-deterministic behavior.
2750 *
2751 * <p>The returned navigable map will be serializable if the specified
2752 * navigable map is serializable.
2753 *
2754 * @param m the navigable map to be "wrapped" in a synchronized navigable
2755 * map
2756 * @return a synchronized view of the specified navigable map.
2757 * @since 1.8
2758 */
2759 public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) {
2760 return new SynchronizedNavigableMap<>(m);
2761 }
2762
2763 /**
2764 * A synchronized NavigableMap.
2765 *
2766 * @serial include
2767 */
2768 static class SynchronizedNavigableMap<K,V>
2769 extends SynchronizedSortedMap<K,V>
2770 implements NavigableMap<K,V>
2771 {
2772 private static final long serialVersionUID = 699392247599746807L;
2773
2774 private final NavigableMap<K,V> nm;
2775
2776 SynchronizedNavigableMap(NavigableMap<K,V> m) {
2777 super(m);
2778 nm = m;
2779 }
2780 SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) {
2781 super(m, mutex);
2782 nm = m;
2783 }
2784
2785 public Entry<K, V> lowerEntry(K key)
2786 { synchronized (mutex) { return nm.lowerEntry(key); } }
2787 public K lowerKey(K key)
2788 { synchronized (mutex) { return nm.lowerKey(key); } }
2789 public Entry<K, V> floorEntry(K key)
2790 { synchronized (mutex) { return nm.floorEntry(key); } }
2791 public K floorKey(K key)
2792 { synchronized (mutex) { return nm.floorKey(key); } }
2793 public Entry<K, V> ceilingEntry(K key)
2794 { synchronized (mutex) { return nm.ceilingEntry(key); } }
2795 public K ceilingKey(K key)
2796 { synchronized (mutex) { return nm.ceilingKey(key); } }
2797 public Entry<K, V> higherEntry(K key)
2798 { synchronized (mutex) { return nm.higherEntry(key); } }
2799 public K higherKey(K key)
2800 { synchronized (mutex) { return nm.higherKey(key); } }
2801 public Entry<K, V> firstEntry()
2802 { synchronized (mutex) { return nm.firstEntry(); } }
2803 public Entry<K, V> lastEntry()
2804 { synchronized (mutex) { return nm.lastEntry(); } }
2805 public Entry<K, V> pollFirstEntry()
2806 { synchronized (mutex) { return nm.pollFirstEntry(); } }
2807 public Entry<K, V> pollLastEntry()
2808 { synchronized (mutex) { return nm.pollLastEntry(); } }
2809
2810 public NavigableMap<K, V> descendingMap() {
2811 synchronized (mutex) {
2812 return
2813 new SynchronizedNavigableMap(nm.descendingMap(), mutex);
2814 }
2815 }
2816
2817 public NavigableSet<K> keySet() {
2818 return navigableKeySet();
2819 }
2820
2821 public NavigableSet<K> navigableKeySet() {
2822 synchronized (mutex) {
2823 return new SynchronizedNavigableSet(nm.navigableKeySet(), mutex);
2824 }
2825 }
2826
2827 public NavigableSet<K> descendingKeySet() {
2828 synchronized (mutex) {
2829 return new SynchronizedNavigableSet(nm.descendingKeySet(), mutex);
2830 }
2831 }
2832
2833
2834 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2835 synchronized (mutex) {
2836 return new SynchronizedNavigableMap<>(
2837 nm.subMap(fromKey, true, toKey, false), mutex);
2838 }
2839 }
2840 public SortedMap<K,V> headMap(K toKey) {
2841 synchronized (mutex) {
2842 return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex);
2843 }
2844 }
2845 public SortedMap<K,V> tailMap(K fromKey) {
2846 synchronized (mutex) {
2847 return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex);
2848 }
2849 }
2850
2851 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
2852 synchronized (mutex) {
2853 return new SynchronizedNavigableMap(
2854 nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex);
2855 }
2856 }
2857
2858 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
2859 synchronized (mutex) {
2860 return new SynchronizedNavigableMap(
2861 nm.headMap(toKey, inclusive), mutex);
2862 }
2863 }
2864
2865 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
2866 synchronized (mutex) {
2867 return new SynchronizedNavigableMap(
2868 nm.tailMap(fromKey, inclusive), mutex);
2869 }
2870 }
2871 }
2872
2873 // Dynamically typesafe collection wrappers
2874
2875 /**
2876 * Returns a dynamically typesafe view of the specified collection.
2877 * Any attempt to insert an element of the wrong type will result in an
2878 * immediate {@link ClassCastException}. Assuming a collection
2879 * contains no incorrectly typed elements prior to the time a
2880 * dynamically typesafe view is generated, and that all subsequent
2881 * access to the collection takes place through the view, it is
2882 * <i>guaranteed</i> that the collection cannot contain an incorrectly
2883 * typed element.
2884 *
2885 * <p>The generics mechanism in the language provides compile-time
2886 * (static) type checking, but it is possible to defeat this mechanism
2887 * with unchecked casts. Usually this is not a problem, as the compiler
2888 * issues warnings on all such unchecked operations. There are, however,
2889 * times when static type checking alone is not sufficient. For example,
2890 * suppose a collection is passed to a third-party library and it is
2891 * imperative that the library code not corrupt the collection by
2892 * inserting an element of the wrong type.
2893 *
2894 * <p>Another use of dynamically typesafe views is debugging. Suppose a
2895 * program fails with a {@code ClassCastException}, indicating that an
2896 * incorrectly typed element was put into a parameterized collection.
2897 * Unfortunately, the exception can occur at any time after the erroneous
2898 * element is inserted, so it typically provides little or no information
2899 * as to the real source of the problem. If the problem is reproducible,
2900 * one can quickly determine its source by temporarily modifying the
2901 * program to wrap the collection with a dynamically typesafe view.
2902 * For example, this declaration:
2903 * <pre> {@code
2904 * Collection<String> c = new HashSet<>();
2905 * }</pre>
2906 * may be replaced temporarily by this one:
2907 * <pre> {@code
2908 * Collection<String> c = Collections.checkedCollection(
2909 * new HashSet<>(), String.class);
2910 * }</pre>
2911 * Running the program again will cause it to fail at the point where
2912 * an incorrectly typed element is inserted into the collection, clearly
2913 * identifying the source of the problem. Once the problem is fixed, the
2914 * modified declaration may be reverted back to the original.
2915 *
2916 * <p>The returned collection does <i>not</i> pass the hashCode and equals
2917 * operations through to the backing collection, but relies on
2918 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
2919 * is necessary to preserve the contracts of these operations in the case
2920 * that the backing collection is a set or a list.
2921 *
2922 * <p>The returned collection will be serializable if the specified
2923 * collection is serializable.
2924 *
2925 * <p>Since {@code null} is considered to be a value of any reference
2926 * type, the returned collection permits insertion of null elements
2927 * whenever the backing collection does.
2928 *
2929 * @param c the collection for which a dynamically typesafe view is to be
2930 * returned
2931 * @param type the type of element that {@code c} is permitted to hold
2932 * @return a dynamically typesafe view of the specified collection
2933 * @since 1.5
2934 */
2935 public static <E> Collection<E> checkedCollection(Collection<E> c,
2936 Class<E> type) {
2937 return new CheckedCollection<>(c, type);
2938 }
2939
2940 @SuppressWarnings("unchecked")
2941 static <T> T[] zeroLengthArray(Class<T> type) {
2942 return (T[]) Array.newInstance(type, 0);
2943 }
2944
2945 /**
2946 * @serial include
2947 */
2948 static class CheckedCollection<E> implements Collection<E>, Serializable {
2949 private static final long serialVersionUID = 1578914078182001775L;
2950
2951 final Collection<E> c;
2952 final Class<E> type;
2953
2954 void typeCheck(Object o) {
2955 if (o != null && !type.isInstance(o))
2956 throw new ClassCastException(badElementMsg(o));
2957 }
2958
2959 private String badElementMsg(Object o) {
2960 return "Attempt to insert " + o.getClass() +
2961 " element into collection with element type " + type;
2962 }
2963
2964 CheckedCollection(Collection<E> c, Class<E> type) {
2965 if (c==null || type == null)
2966 throw new NullPointerException();
2967 this.c = c;
2968 this.type = type;
2969 }
2970
2971 public int size() { return c.size(); }
2972 public boolean isEmpty() { return c.isEmpty(); }
2973 public boolean contains(Object o) { return c.contains(o); }
2974 public Object[] toArray() { return c.toArray(); }
2975 public <T> T[] toArray(T[] a) { return c.toArray(a); }
2976 public String toString() { return c.toString(); }
2977 public boolean remove(Object o) { return c.remove(o); }
2978 public void clear() { c.clear(); }
2979
2980 public boolean containsAll(Collection<?> coll) {
2981 return c.containsAll(coll);
2982 }
2983 public boolean removeAll(Collection<?> coll) {
2984 return c.removeAll(coll);
2985 }
2986 public boolean retainAll(Collection<?> coll) {
2987 return c.retainAll(coll);
2988 }
2989
2990 public Iterator<E> iterator() {
2991 // JDK-6363904 - unwrapped iterator could be typecast to
2992 // ListIterator with unsafe set()
2993 final Iterator<E> it = c.iterator();
2994 return new Iterator<E>() {
2995 public boolean hasNext() { return it.hasNext(); }
2996 public E next() { return it.next(); }
2997 public void remove() { it.remove(); }};
2998 }
2999
3000 public boolean add(E e) {
3001 typeCheck(e);
3002 return c.add(e);
3003 }
3004
3005 private E[] zeroLengthElementArray = null; // Lazily initialized
3006
3007 private E[] zeroLengthElementArray() {
3008 return zeroLengthElementArray != null ? zeroLengthElementArray :
3009 (zeroLengthElementArray = zeroLengthArray(type));
3010 }
3011
3012 @SuppressWarnings("unchecked")
3013 Collection<E> checkedCopyOf(Collection<? extends E> coll) {
3014 Object[] a = null;
3015 try {
3016 E[] z = zeroLengthElementArray();
3017 a = coll.toArray(z);
3018 // Defend against coll violating the toArray contract
3019 if (a.getClass() != z.getClass())
3020 a = Arrays.copyOf(a, a.length, z.getClass());
3021 } catch (ArrayStoreException ignore) {
3022 // To get better and consistent diagnostics,
3023 // we call typeCheck explicitly on each element.
3024 // We call clone() to defend against coll retaining a
3025 // reference to the returned array and storing a bad
3026 // element into it after it has been type checked.
3027 a = coll.toArray().clone();
3028 for (Object o : a)
3029 typeCheck(o);
3030 }
3031 // A slight abuse of the type system, but safe here.
3032 return (Collection<E>) Arrays.asList(a);
3033 }
3034
3035 public boolean addAll(Collection<? extends E> coll) {
3036 // Doing things this way insulates us from concurrent changes
3037 // in the contents of coll and provides all-or-nothing
3038 // semantics (which we wouldn't get if we type-checked each
3039 // element as we added it)
3040 return c.addAll(checkedCopyOf(coll));
3041 }
3042
3043 // Override default methods in Collection
3044 @Override
3045 public void forEach(Consumer<? super E> action) {c.forEach(action);}
3046 @Override
3047 public boolean removeIf(Predicate<? super E> filter) {
3048 return c.removeIf(filter);
3049 }
3050 @Override
3051 public Spliterator<E> spliterator() {return c.spliterator();}
3052 }
3053
3054 /**
3055 * Returns a dynamically typesafe view of the specified queue.
3056 * Any attempt to insert an element of the wrong type will result in
3057 * an immediate {@link ClassCastException}. Assuming a queue contains
3058 * no incorrectly typed elements prior to the time a dynamically typesafe
3059 * view is generated, and that all subsequent access to the queue
3060 * takes place through the view, it is <i>guaranteed</i> that the
3061 * queue cannot contain an incorrectly typed element.
3062 *
3063 * <p>A discussion of the use of dynamically typesafe views may be
3064 * found in the documentation for the {@link #checkedCollection
3065 * checkedCollection} method.
3066 *
3067 * <p>The returned queue will be serializable if the specified queue
3068 * is serializable.
3069 *
3070 * <p>Since {@code null} is considered to be a value of any reference
3071 * type, the returned queue permits insertion of {@code null} elements
3072 * whenever the backing queue does.
3073 *
3074 * @param queue the queue for which a dynamically typesafe view is to be
3075 * returned
3076 * @param type the type of element that {@code queue} is permitted to hold
3077 * @return a dynamically typesafe view of the specified queue
3078 * @since 1.8
3079 */
3080 public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) {
3081 return new CheckedQueue<>(queue, type);
3082 }
3083
3084 /**
3085 * @serial include
3086 */
3087 static class CheckedQueue<E>
3088 extends CheckedCollection<E>
3089 implements Queue<E>, Serializable
3090 {
3091 private static final long serialVersionUID = 1433151992604707767L;
3092 final Queue<E> queue;
3093
3094 CheckedQueue(Queue<E> queue, Class<E> elementType) {
3095 super(queue, elementType);
3096 this.queue = queue;
3097 }
3098
3099 public E element() {return queue.element();}
3100 public boolean equals(Object o) {return o == this || c.equals(o);}
3101 public int hashCode() {return c.hashCode();}
3102 public E peek() {return queue.peek();}
3103 public E poll() {return queue.poll();}
3104 public E remove() {return queue.remove();}
3105
3106 public boolean offer(E e) {
3107 typeCheck(e);
3108 return add(e);
3109 }
3110 }
3111
3112 /**
3113 * Returns a dynamically typesafe view of the specified set.
3114 * Any attempt to insert an element of the wrong type will result in
3115 * an immediate {@link ClassCastException}. Assuming a set contains
3116 * no incorrectly typed elements prior to the time a dynamically typesafe
3117 * view is generated, and that all subsequent access to the set
3118 * takes place through the view, it is <i>guaranteed</i> that the
3119 * set cannot contain an incorrectly typed element.
3120 *
3121 * <p>A discussion of the use of dynamically typesafe views may be
3122 * found in the documentation for the {@link #checkedCollection
3123 * checkedCollection} method.
3124 *
3125 * <p>The returned set will be serializable if the specified set is
3126 * serializable.
3127 *
3128 * <p>Since {@code null} is considered to be a value of any reference
3129 * type, the returned set permits insertion of null elements whenever
3130 * the backing set does.
3131 *
3132 * @param s the set for which a dynamically typesafe view is to be
3133 * returned
3134 * @param type the type of element that {@code s} is permitted to hold
3135 * @return a dynamically typesafe view of the specified set
3136 * @since 1.5
3137 */
3138 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
3139 return new CheckedSet<>(s, type);
3140 }
3141
3142 /**
3143 * @serial include
3144 */
3145 static class CheckedSet<E> extends CheckedCollection<E>
3146 implements Set<E>, Serializable
3147 {
3148 private static final long serialVersionUID = 4694047833775013803L;
3149
3150 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
3151
3152 public boolean equals(Object o) { return o == this || c.equals(o); }
3153 public int hashCode() { return c.hashCode(); }
3154 }
3155
3156 /**
3157 * Returns a dynamically typesafe view of the specified sorted set.
3158 * Any attempt to insert an element of the wrong type will result in an
3159 * immediate {@link ClassCastException}. Assuming a sorted set
3160 * contains no incorrectly typed elements prior to the time a
3161 * dynamically typesafe view is generated, and that all subsequent
3162 * access to the sorted set takes place through the view, it is
3163 * <i>guaranteed</i> that the sorted set cannot contain an incorrectly
3164 * typed element.
3165 *
3166 * <p>A discussion of the use of dynamically typesafe views may be
3167 * found in the documentation for the {@link #checkedCollection
3168 * checkedCollection} method.
3169 *
3170 * <p>The returned sorted set will be serializable if the specified sorted
3171 * set is serializable.
3172 *
3173 * <p>Since {@code null} is considered to be a value of any reference
3174 * type, the returned sorted set permits insertion of null elements
3175 * whenever the backing sorted set does.
3176 *
3177 * @param s the sorted set for which a dynamically typesafe view is to be
3178 * returned
3179 * @param type the type of element that {@code s} is permitted to hold
3180 * @return a dynamically typesafe view of the specified sorted set
3181 * @since 1.5
3182 */
3183 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
3184 Class<E> type) {
3185 return new CheckedSortedSet<>(s, type);
3186 }
3187
3188 /**
3189 * @serial include
3190 */
3191 static class CheckedSortedSet<E> extends CheckedSet<E>
3192 implements SortedSet<E>, Serializable
3193 {
3194 private static final long serialVersionUID = 1599911165492914959L;
3195
3196 private final SortedSet<E> ss;
3197
3198 CheckedSortedSet(SortedSet<E> s, Class<E> type) {
3199 super(s, type);
3200 ss = s;
3201 }
3202
3203 public Comparator<? super E> comparator() { return ss.comparator(); }
3204 public E first() { return ss.first(); }
3205 public E last() { return ss.last(); }
3206
3207 public SortedSet<E> subSet(E fromElement, E toElement) {
3208 return checkedSortedSet(ss.subSet(fromElement,toElement), type);
3209 }
3210 public SortedSet<E> headSet(E toElement) {
3211 return checkedSortedSet(ss.headSet(toElement), type);
3212 }
3213 public SortedSet<E> tailSet(E fromElement) {
3214 return checkedSortedSet(ss.tailSet(fromElement), type);
3215 }
3216 }
3217
3218 /**
3219 * Returns a dynamically typesafe view of the specified navigable set.
3220 * Any attempt to insert an element of the wrong type will result in an
3221 * immediate {@link ClassCastException}. Assuming a navigable set
3222 * contains no incorrectly typed elements prior to the time a
3223 * dynamically typesafe view is generated, and that all subsequent
3224 * access to the navigable set takes place through the view, it is
3225 * <em>guaranteed</em> that the navigable set cannot contain an incorrectly
3226 * typed element.
3227 *
3228 * <p>A discussion of the use of dynamically typesafe views may be
3229 * found in the documentation for the {@link #checkedCollection
3230 * checkedCollection} method.
3231 *
3232 * <p>The returned navigable set will be serializable if the specified
3233 * navigable set is serializable.
3234 *
3235 * <p>Since {@code null} is considered to be a value of any reference
3236 * type, the returned navigable set permits insertion of null elements
3237 * whenever the backing sorted set does.
3238 *
3239 * @param s the navigable set for which a dynamically typesafe view is to be
3240 * returned
3241 * @param type the type of element that {@code s} is permitted to hold
3242 * @return a dynamically typesafe view of the specified navigable set
3243 * @since 1.8
3244 */
3245 public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s,
3246 Class<E> type) {
3247 return new CheckedNavigableSet<>(s, type);
3248 }
3249
3250 /**
3251 * @serial include
3252 */
3253 static class CheckedNavigableSet<E> extends CheckedSortedSet<E>
3254 implements NavigableSet<E>, Serializable
3255 {
3256 private static final long serialVersionUID = -5429120189805438922L;
3257
3258 private final NavigableSet<E> ns;
3259
3260 CheckedNavigableSet(NavigableSet<E> s, Class<E> type) {
3261 super(s, type);
3262 ns = s;
3263 }
3264
3265 public E lower(E e) { return ns.lower(e); }
3266 public E floor(E e) { return ns.floor(e); }
3267 public E ceiling(E e) { return ns.ceiling(e); }
3268 public E higher(E e) { return ns.higher(e); }
3269 public E pollFirst() { return ns.pollFirst(); }
3270 public E pollLast() {return ns.pollLast(); }
3271 public NavigableSet<E> descendingSet()
3272 { return checkedNavigableSet(ns.descendingSet(), type); }
3273 public Iterator<E> descendingIterator()
3274 {return checkedNavigableSet(ns.descendingSet(), type).iterator(); }
3275
3276 public NavigableSet<E> subSet(E fromElement, E toElement) {
3277 return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type);
3278 }
3279 public NavigableSet<E> headSet(E toElement) {
3280 return checkedNavigableSet(ns.headSet(toElement, false), type);
3281 }
3282 public NavigableSet<E> tailSet(E fromElement) {
3283 return checkedNavigableSet(ns.tailSet(fromElement, true), type);
3284 }
3285
3286 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
3287 return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type);
3288 }
3289
3290 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
3291 return checkedNavigableSet(ns.headSet(toElement, inclusive), type);
3292 }
3293
3294 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
3295 return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type);
3296 }
3297 }
3298
3299 /**
3300 * Returns a dynamically typesafe view of the specified list.
3301 * Any attempt to insert an element of the wrong type will result in
3302 * an immediate {@link ClassCastException}. Assuming a list contains
3303 * no incorrectly typed elements prior to the time a dynamically typesafe
3304 * view is generated, and that all subsequent access to the list
3305 * takes place through the view, it is <i>guaranteed</i> that the
3306 * list cannot contain an incorrectly typed element.
3307 *
3308 * <p>A discussion of the use of dynamically typesafe views may be
3309 * found in the documentation for the {@link #checkedCollection
3310 * checkedCollection} method.
3311 *
3312 * <p>The returned list will be serializable if the specified list
3313 * is serializable.
3314 *
3315 * <p>Since {@code null} is considered to be a value of any reference
3316 * type, the returned list permits insertion of null elements whenever
3317 * the backing list does.
3318 *
3319 * @param list the list for which a dynamically typesafe view is to be
3320 * returned
3321 * @param type the type of element that {@code list} is permitted to hold
3322 * @return a dynamically typesafe view of the specified list
3323 * @since 1.5
3324 */
3325 public static <E> List<E> checkedList(List<E> list, Class<E> type) {
3326 return (list instanceof RandomAccess ?
3327 new CheckedRandomAccessList<>(list, type) :
3328 new CheckedList<>(list, type));
3329 }
3330
3331 /**
3332 * @serial include
3333 */
3334 static class CheckedList<E>
3335 extends CheckedCollection<E>
3336 implements List<E>
3337 {
3338 private static final long serialVersionUID = 65247728283967356L;
3339 final List<E> list;
3340
3341 CheckedList(List<E> list, Class<E> type) {
3342 super(list, type);
3343 this.list = list;
3344 }
3345
3346 public boolean equals(Object o) { return o == this || list.equals(o); }
3347 public int hashCode() { return list.hashCode(); }
3348 public E get(int index) { return list.get(index); }
3349 public E remove(int index) { return list.remove(index); }
3350 public int indexOf(Object o) { return list.indexOf(o); }
3351 public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
3352
3353 public E set(int index, E element) {
3354 typeCheck(element);
3355 return list.set(index, element);
3356 }
3357
3358 public void add(int index, E element) {
3359 typeCheck(element);
3360 list.add(index, element);
3361 }
3362
3363 public boolean addAll(int index, Collection<? extends E> c) {
3364 return list.addAll(index, checkedCopyOf(c));
3365 }
3366 public ListIterator<E> listIterator() { return listIterator(0); }
3367
3368 public ListIterator<E> listIterator(final int index) {
3369 final ListIterator<E> i = list.listIterator(index);
3370
3371 return new ListIterator<E>() {
3372 public boolean hasNext() { return i.hasNext(); }
3373 public E next() { return i.next(); }
3374 public boolean hasPrevious() { return i.hasPrevious(); }
3375 public E previous() { return i.previous(); }
3376 public int nextIndex() { return i.nextIndex(); }
3377 public int previousIndex() { return i.previousIndex(); }
3378 public void remove() { i.remove(); }
3379
3380 public void set(E e) {
3381 typeCheck(e);
3382 i.set(e);
3383 }
3384
3385 public void add(E e) {
3386 typeCheck(e);
3387 i.add(e);
3388 }
3389
3390 @Override
3391 public void forEachRemaining(Consumer<? super E> action) {
3392 i.forEachRemaining(action);
3393 }
3394 };
3395 }
3396
3397 public List<E> subList(int fromIndex, int toIndex) {
3398 return new CheckedList<>(list.subList(fromIndex, toIndex), type);
3399 }
3400
3401 @Override
3402 public void replaceAll(UnaryOperator<E> operator) {
3403 list.replaceAll(operator);
3404 }
3405 @Override
3406 public void sort(Comparator<? super E> c) {
3407 list.sort(c);
3408 }
3409 }
3410
3411 /**
3412 * @serial include
3413 */
3414 static class CheckedRandomAccessList<E> extends CheckedList<E>
3415 implements RandomAccess
3416 {
3417 private static final long serialVersionUID = 1638200125423088369L;
3418
3419 CheckedRandomAccessList(List<E> list, Class<E> type) {
3420 super(list, type);
3421 }
3422
3423 public List<E> subList(int fromIndex, int toIndex) {
3424 return new CheckedRandomAccessList<>(
3425 list.subList(fromIndex, toIndex), type);
3426 }
3427 }
3428
3429 /**
3430 * Returns a dynamically typesafe view of the specified map.
3431 * Any attempt to insert a mapping whose key or value have the wrong
3432 * type will result in an immediate {@link ClassCastException}.
3433 * Similarly, any attempt to modify the value currently associated with
3434 * a key will result in an immediate {@link ClassCastException},
3435 * whether the modification is attempted directly through the map
3436 * itself, or through a {@link Map.Entry} instance obtained from the
3437 * map's {@link Map#entrySet() entry set} view.
3438 *
3439 * <p>Assuming a map contains no incorrectly typed keys or values
3440 * prior to the time a dynamically typesafe view is generated, and
3441 * that all subsequent access to the map takes place through the view
3442 * (or one of its collection views), it is <i>guaranteed</i> that the
3443 * map cannot contain an incorrectly typed key or value.
3444 *
3445 * <p>A discussion of the use of dynamically typesafe views may be
3446 * found in the documentation for the {@link #checkedCollection
3447 * checkedCollection} method.
3448 *
3449 * <p>The returned map will be serializable if the specified map is
3450 * serializable.
3451 *
3452 * <p>Since {@code null} is considered to be a value of any reference
3453 * type, the returned map permits insertion of null keys or values
3454 * whenever the backing map does.
3455 *
3456 * @param m the map for which a dynamically typesafe view is to be
3457 * returned
3458 * @param keyType the type of key that {@code m} is permitted to hold
3459 * @param valueType the type of value that {@code m} is permitted to hold
3460 * @return a dynamically typesafe view of the specified map
3461 * @since 1.5
3462 */
3463 public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
3464 Class<K> keyType,
3465 Class<V> valueType) {
3466 return new CheckedMap<>(m, keyType, valueType);
3467 }
3468
3469
3470 /**
3471 * @serial include
3472 */
3473 private static class CheckedMap<K,V>
3474 implements Map<K,V>, Serializable
3475 {
3476 private static final long serialVersionUID = 5742860141034234728L;
3477
3478 private final Map<K, V> m;
3479 final Class<K> keyType;
3480 final Class<V> valueType;
3481
3482 private void typeCheck(Object key, Object value) {
3483 if (key != null && !keyType.isInstance(key))
3484 throw new ClassCastException(badKeyMsg(key));
3485
3486 if (value != null && !valueType.isInstance(value))
3487 throw new ClassCastException(badValueMsg(value));
3488 }
3489
3490 private BiFunction<? super K, ? super V, ? extends V> typeCheck(
3491 BiFunction<? super K, ? super V, ? extends V> func) {
3492 Objects.requireNonNull(func);
3493 return (k, v) -> {
3494 V newValue = func.apply(k, v);
3495 typeCheck(k, newValue);
3496 return newValue;
3497 };
3498 }
3499
3500 private String badKeyMsg(Object key) {
3501 return "Attempt to insert " + key.getClass() +
3502 " key into map with key type " + keyType;
3503 }
3504
3505 private String badValueMsg(Object value) {
3506 return "Attempt to insert " + value.getClass() +
3507 " value into map with value type " + valueType;
3508 }
3509
3510 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
3511 this.m = Objects.requireNonNull(m);
3512 this.keyType = Objects.requireNonNull(keyType);
3513 this.valueType = Objects.requireNonNull(valueType);
3514 }
3515
3516 public int size() { return m.size(); }
3517 public boolean isEmpty() { return m.isEmpty(); }
3518 public boolean containsKey(Object key) { return m.containsKey(key); }
3519 public boolean containsValue(Object v) { return m.containsValue(v); }
3520 public V get(Object key) { return m.get(key); }
3521 public V remove(Object key) { return m.remove(key); }
3522 public void clear() { m.clear(); }
3523 public Set<K> keySet() { return m.keySet(); }
3524 public Collection<V> values() { return m.values(); }
3525 public boolean equals(Object o) { return o == this || m.equals(o); }
3526 public int hashCode() { return m.hashCode(); }
3527 public String toString() { return m.toString(); }
3528
3529 public V put(K key, V value) {
3530 typeCheck(key, value);
3531 return m.put(key, value);
3532 }
3533
3534 @SuppressWarnings("unchecked")
3535 public void putAll(Map<? extends K, ? extends V> t) {
3536 // Satisfy the following goals:
3537 // - good diagnostics in case of type mismatch
3538 // - all-or-nothing semantics
3539 // - protection from malicious t
3540 // - correct behavior if t is a concurrent map
3541 Object[] entries = t.entrySet().toArray();
3542 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length);
3543 for (Object o : entries) {
3544 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3545 Object k = e.getKey();
3546 Object v = e.getValue();
3547 typeCheck(k, v);
3548 checked.add(
3549 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v));
3550 }
3551 for (Map.Entry<K,V> e : checked)
3552 m.put(e.getKey(), e.getValue());
3553 }
3554
3555 private transient Set<Map.Entry<K,V>> entrySet = null;
3556
3557 public Set<Map.Entry<K,V>> entrySet() {
3558 if (entrySet==null)
3559 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
3560 return entrySet;
3561 }
3562
3563 // Override default methods in Map
3564 @Override
3565 public void forEach(BiConsumer<? super K, ? super V> action) {
3566 m.forEach(action);
3567 }
3568
3569 @Override
3570 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
3571 m.replaceAll(typeCheck(function));
3572 }
3573
3574 @Override
3575 public V putIfAbsent(K key, V value) {
3576 typeCheck(key, value);
3577 return m.putIfAbsent(key, value);
3578 }
3579
3580 @Override
3581 public boolean remove(Object key, Object value) {
3582 return m.remove(key, value);
3583 }
3584
3585 @Override
3586 public boolean replace(K key, V oldValue, V newValue) {
3587 typeCheck(key, newValue);
3588 return m.replace(key, oldValue, newValue);
3589 }
3590
3591 @Override
3592 public V replace(K key, V value) {
3593 typeCheck(key, value);
3594 return m.replace(key, value);
3595 }
3596
3597 @Override
3598 public V computeIfAbsent(K key,
3599 Function<? super K, ? extends V> mappingFunction) {
3600 Objects.requireNonNull(mappingFunction);
3601 return m.computeIfAbsent(key, k -> {
3602 V value = mappingFunction.apply(k);
3603 typeCheck(k, value);
3604 return value;
3605 });
3606 }
3607
3608 @Override
3609 public V computeIfPresent(K key,
3610 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3611 return m.computeIfPresent(key, typeCheck(remappingFunction));
3612 }
3613
3614 @Override
3615 public V compute(K key,
3616 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3617 return m.compute(key, typeCheck(remappingFunction));
3618 }
3619
3620 @Override
3621 public V merge(K key, V value,
3622 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
3623 Objects.requireNonNull(remappingFunction);
3624 return m.merge(key, value, (v1, v2) -> {
3625 V newValue = remappingFunction.apply(v1, v2);
3626 typeCheck(null, newValue);
3627 return newValue;
3628 });
3629 }
3630
3631 /**
3632 * We need this class in addition to CheckedSet as Map.Entry permits
3633 * modification of the backing Map via the setValue operation. This
3634 * class is subtle: there are many possible attacks that must be
3635 * thwarted.
3636 *
3637 * @serial exclude
3638 */
3639 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
3640 private final Set<Map.Entry<K,V>> s;
3641 private final Class<V> valueType;
3642
3643 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
3644 this.s = s;
3645 this.valueType = valueType;
3646 }
3647
3648 public int size() { return s.size(); }
3649 public boolean isEmpty() { return s.isEmpty(); }
3650 public String toString() { return s.toString(); }
3651 public int hashCode() { return s.hashCode(); }
3652 public void clear() { s.clear(); }
3653
3654 public boolean add(Map.Entry<K, V> e) {
3655 throw new UnsupportedOperationException();
3656 }
3657 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
3658 throw new UnsupportedOperationException();
3659 }
3660
3661 public Iterator<Map.Entry<K,V>> iterator() {
3662 final Iterator<Map.Entry<K, V>> i = s.iterator();
3663 final Class<V> valueType = this.valueType;
3664
3665 return new Iterator<Map.Entry<K,V>>() {
3666 public boolean hasNext() { return i.hasNext(); }
3667 public void remove() { i.remove(); }
3668
3669 public Map.Entry<K,V> next() {
3670 return checkedEntry(i.next(), valueType);
3671 }
3672 };
3673 }
3674
3675 @SuppressWarnings("unchecked")
3676 public Object[] toArray() {
3677 Object[] source = s.toArray();
3678
3679 /*
3680 * Ensure that we don't get an ArrayStoreException even if
3681 * s.toArray returns an array of something other than Object
3682 */
3683 Object[] dest = (CheckedEntry.class.isInstance(
3684 source.getClass().getComponentType()) ? source :
3685 new Object[source.length]);
3686
3687 for (int i = 0; i < source.length; i++)
3688 dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
3689 valueType);
3690 return dest;
3691 }
3692
3693 @SuppressWarnings("unchecked")
3694 public <T> T[] toArray(T[] a) {
3695 // We don't pass a to s.toArray, to avoid window of
3696 // vulnerability wherein an unscrupulous multithreaded client
3697 // could get his hands on raw (unwrapped) Entries from s.
3698 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
3699
3700 for (int i=0; i<arr.length; i++)
3701 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
3702 valueType);
3703 if (arr.length > a.length)
3704 return arr;
3705
3706 System.arraycopy(arr, 0, a, 0, arr.length);
3707 if (a.length > arr.length)
3708 a[arr.length] = null;
3709 return a;
3710 }
3711
3712 /**
3713 * This method is overridden to protect the backing set against
3714 * an object with a nefarious equals function that senses
3715 * that the equality-candidate is Map.Entry and calls its
3716 * setValue method.
3717 */
3718 public boolean contains(Object o) {
3719 if (!(o instanceof Map.Entry))
3720 return false;
3721 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3722 return s.contains(
3723 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
3724 }
3725
3726 /**
3727 * The bulk collection methods are overridden to protect
3728 * against an unscrupulous collection whose contains(Object o)
3729 * method senses when o is a Map.Entry, and calls o.setValue.
3730 */
3731 public boolean containsAll(Collection<?> c) {
3732 for (Object o : c)
3733 if (!contains(o)) // Invokes safe contains() above
3734 return false;
3735 return true;
3736 }
3737
3738 public boolean remove(Object o) {
3739 if (!(o instanceof Map.Entry))
3740 return false;
3741 return s.remove(new AbstractMap.SimpleImmutableEntry
3742 <>((Map.Entry<?,?>)o));
3743 }
3744
3745 public boolean removeAll(Collection<?> c) {
3746 return batchRemove(c, false);
3747 }
3748 public boolean retainAll(Collection<?> c) {
3749 return batchRemove(c, true);
3750 }
3751 private boolean batchRemove(Collection<?> c, boolean complement) {
3752 boolean modified = false;
3753 Iterator<Map.Entry<K,V>> it = iterator();
3754 while (it.hasNext()) {
3755 if (c.contains(it.next()) != complement) {
3756 it.remove();
3757 modified = true;
3758 }
3759 }
3760 return modified;
3761 }
3762
3763 public boolean equals(Object o) {
3764 if (o == this)
3765 return true;
3766 if (!(o instanceof Set))
3767 return false;
3768 Set<?> that = (Set<?>) o;
3769 return that.size() == s.size()
3770 && containsAll(that); // Invokes safe containsAll() above
3771 }
3772
3773 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
3774 Class<T> valueType) {
3775 return new CheckedEntry<>(e, valueType);
3776 }
3777
3778 /**
3779 * This "wrapper class" serves two purposes: it prevents
3780 * the client from modifying the backing Map, by short-circuiting
3781 * the setValue method, and it protects the backing Map against
3782 * an ill-behaved Map.Entry that attempts to modify another
3783 * Map.Entry when asked to perform an equality check.
3784 */
3785 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
3786 private final Map.Entry<K, V> e;
3787 private final Class<T> valueType;
3788
3789 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
3790 this.e = Objects.requireNonNull(e);
3791 this.valueType = Objects.requireNonNull(valueType);
3792 }
3793
3794 public K getKey() { return e.getKey(); }
3795 public V getValue() { return e.getValue(); }
3796 public int hashCode() { return e.hashCode(); }
3797 public String toString() { return e.toString(); }
3798
3799 public V setValue(V value) {
3800 if (value != null && !valueType.isInstance(value))
3801 throw new ClassCastException(badValueMsg(value));
3802 return e.setValue(value);
3803 }
3804
3805 private String badValueMsg(Object value) {
3806 return "Attempt to insert " + value.getClass() +
3807 " value into map with value type " + valueType;
3808 }
3809
3810 public boolean equals(Object o) {
3811 if (o == this)
3812 return true;
3813 if (!(o instanceof Map.Entry))
3814 return false;
3815 return e.equals(new AbstractMap.SimpleImmutableEntry
3816 <>((Map.Entry<?,?>)o));
3817 }
3818 }
3819 }
3820 }
3821
3822 /**
3823 * Returns a dynamically typesafe view of the specified sorted map.
3824 * Any attempt to insert a mapping whose key or value have the wrong
3825 * type will result in an immediate {@link ClassCastException}.
3826 * Similarly, any attempt to modify the value currently associated with
3827 * a key will result in an immediate {@link ClassCastException},
3828 * whether the modification is attempted directly through the map
3829 * itself, or through a {@link Map.Entry} instance obtained from the
3830 * map's {@link Map#entrySet() entry set} view.
3831 *
3832 * <p>Assuming a map contains no incorrectly typed keys or values
3833 * prior to the time a dynamically typesafe view is generated, and
3834 * that all subsequent access to the map takes place through the view
3835 * (or one of its collection views), it is <i>guaranteed</i> that the
3836 * map cannot contain an incorrectly typed key or value.
3837 *
3838 * <p>A discussion of the use of dynamically typesafe views may be
3839 * found in the documentation for the {@link #checkedCollection
3840 * checkedCollection} method.
3841 *
3842 * <p>The returned map will be serializable if the specified map is
3843 * serializable.
3844 *
3845 * <p>Since {@code null} is considered to be a value of any reference
3846 * type, the returned map permits insertion of null keys or values
3847 * whenever the backing map does.
3848 *
3849 * @param m the map for which a dynamically typesafe view is to be
3850 * returned
3851 * @param keyType the type of key that {@code m} is permitted to hold
3852 * @param valueType the type of value that {@code m} is permitted to hold
3853 * @return a dynamically typesafe view of the specified map
3854 * @since 1.5
3855 */
3856 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
3857 Class<K> keyType,
3858 Class<V> valueType) {
3859 return new CheckedSortedMap<>(m, keyType, valueType);
3860 }
3861
3862 /**
3863 * @serial include
3864 */
3865 static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
3866 implements SortedMap<K,V>, Serializable
3867 {
3868 private static final long serialVersionUID = 1599671320688067438L;
3869
3870 private final SortedMap<K, V> sm;
3871
3872 CheckedSortedMap(SortedMap<K, V> m,
3873 Class<K> keyType, Class<V> valueType) {
3874 super(m, keyType, valueType);
3875 sm = m;
3876 }
3877
3878 public Comparator<? super K> comparator() { return sm.comparator(); }
3879 public K firstKey() { return sm.firstKey(); }
3880 public K lastKey() { return sm.lastKey(); }
3881
3882 public SortedMap<K,V> subMap(K fromKey, K toKey) {
3883 return checkedSortedMap(sm.subMap(fromKey, toKey),
3884 keyType, valueType);
3885 }
3886 public SortedMap<K,V> headMap(K toKey) {
3887 return checkedSortedMap(sm.headMap(toKey), keyType, valueType);
3888 }
3889 public SortedMap<K,V> tailMap(K fromKey) {
3890 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType);
3891 }
3892 }
3893
3894 /**
3895 * Returns a dynamically typesafe view of the specified navigable map.
3896 * Any attempt to insert a mapping whose key or value have the wrong
3897 * type will result in an immediate {@link ClassCastException}.
3898 * Similarly, any attempt to modify the value currently associated with
3899 * a key will result in an immediate {@link ClassCastException},
3900 * whether the modification is attempted directly through the map
3901 * itself, or through a {@link Map.Entry} instance obtained from the
3902 * map's {@link Map#entrySet() entry set} view.
3903 *
3904 * <p>Assuming a map contains no incorrectly typed keys or values
3905 * prior to the time a dynamically typesafe view is generated, and
3906 * that all subsequent access to the map takes place through the view
3907 * (or one of its collection views), it is <em>guaranteed</em> that the
3908 * map cannot contain an incorrectly typed key or value.
3909 *
3910 * <p>A discussion of the use of dynamically typesafe views may be
3911 * found in the documentation for the {@link #checkedCollection
3912 * checkedCollection} method.
3913 *
3914 * <p>The returned map will be serializable if the specified map is
3915 * serializable.
3916 *
3917 * <p>Since {@code null} is considered to be a value of any reference
3918 * type, the returned map permits insertion of null keys or values
3919 * whenever the backing map does.
3920 *
3921 * @param <K> type of map keys
3922 * @param <V> type of map values
3923 * @param m the map for which a dynamically typesafe view is to be
3924 * returned
3925 * @param keyType the type of key that {@code m} is permitted to hold
3926 * @param valueType the type of value that {@code m} is permitted to hold
3927 * @return a dynamically typesafe view of the specified map
3928 * @since 1.8
3929 */
3930 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m,
3931 Class<K> keyType,
3932 Class<V> valueType) {
3933 return new CheckedNavigableMap<>(m, keyType, valueType);
3934 }
3935
3936 /**
3937 * @serial include
3938 */
3939 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V>
3940 implements NavigableMap<K,V>, Serializable
3941 {
3942 private static final long serialVersionUID = -4852462692372534096L;
3943
3944 private final NavigableMap<K, V> nm;
3945
3946 CheckedNavigableMap(NavigableMap<K, V> m,
3947 Class<K> keyType, Class<V> valueType) {
3948 super(m, keyType, valueType);
3949 nm = m;
3950 }
3951
3952 public Comparator<? super K> comparator() { return nm.comparator(); }
3953 public K firstKey() { return nm.firstKey(); }
3954 public K lastKey() { return nm.lastKey(); }
3955
3956 public Entry<K, V> lowerEntry(K key) {
3957 Entry<K,V> lower = nm.lowerEntry(key);
3958 return (null != lower)
3959 ? new CheckedMap.CheckedEntrySet.CheckedEntry(lower, valueType)
3960 : null;
3961 }
3962
3963 public K lowerKey(K key) { return nm.lowerKey(key); }
3964
3965 public Entry<K, V> floorEntry(K key) {
3966 Entry<K,V> floor = nm.floorEntry(key);
3967 return (null != floor)
3968 ? new CheckedMap.CheckedEntrySet.CheckedEntry(floor, valueType)
3969 : null;
3970 }
3971
3972 public K floorKey(K key) { return nm.floorKey(key); }
3973
3974 public Entry<K, V> ceilingEntry(K key) {
3975 Entry<K,V> ceiling = nm.ceilingEntry(key);
3976 return (null != ceiling)
3977 ? new CheckedMap.CheckedEntrySet.CheckedEntry(ceiling, valueType)
3978 : null;
3979 }
3980
3981 public K ceilingKey(K key) { return nm.ceilingKey(key); }
3982
3983 public Entry<K, V> higherEntry(K key) {
3984 Entry<K,V> higher = nm.higherEntry(key);
3985 return (null != higher)
3986 ? new CheckedMap.CheckedEntrySet.CheckedEntry(higher, valueType)
3987 : null;
3988 }
3989
3990 public K higherKey(K key) { return nm.higherKey(key); }
3991
3992 public Entry<K, V> firstEntry() {
3993 Entry<K,V> first = nm.firstEntry();
3994 return (null != first)
3995 ? new CheckedMap.CheckedEntrySet.CheckedEntry(first, valueType)
3996 : null;
3997 }
3998
3999 public Entry<K, V> lastEntry() {
4000 Entry<K,V> last = nm.lastEntry();
4001 return (null != last)
4002 ? new CheckedMap.CheckedEntrySet.CheckedEntry(last, valueType)
4003 : null;
4004 }
4005
4006 public Entry<K, V> pollFirstEntry() {
4007 Entry<K,V> entry = nm.pollFirstEntry();
4008 return (null == entry)
4009 ? null
4010 : new CheckedMap.CheckedEntrySet.CheckedEntry(entry, valueType);
4011 }
4012
4013 public Entry<K, V> pollLastEntry() {
4014 Entry<K,V> entry = nm.pollLastEntry();
4015 return (null == entry)
4016 ? null
4017 : new CheckedMap.CheckedEntrySet.CheckedEntry(entry, valueType);
4018 }
4019
4020 public NavigableMap<K, V> descendingMap() {
4021 return checkedNavigableMap(nm.descendingMap(), keyType, valueType);
4022 }
4023
4024 public NavigableSet<K> keySet() {
4025 return navigableKeySet();
4026 }
4027
4028 public NavigableSet<K> navigableKeySet() {
4029 return checkedNavigableSet(nm.navigableKeySet(), keyType);
4030 }
4031
4032 public NavigableSet<K> descendingKeySet() {
4033 return checkedNavigableSet(nm.descendingKeySet(), keyType);
4034 }
4035
4036 @Override
4037 public NavigableMap<K,V> subMap(K fromKey, K toKey) {
4038 return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false),
4039 keyType, valueType);
4040 }
4041
4042 @Override
4043 public NavigableMap<K,V> headMap(K toKey) {
4044 return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType);
4045 }
4046
4047 @Override
4048 public NavigableMap<K,V> tailMap(K fromKey) {
4049 return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType);
4050 }
4051
4052 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
4053 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType);
4054 }
4055
4056 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
4057 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType);
4058 }
4059
4060 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
4061 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType);
4062 }
4063 }
4064
4065 // Empty collections
4066
4067 /**
4068 * Returns an iterator that has no elements. More precisely,
4069 *
4070 * <ul compact>
4071 *
4072 * <li>{@link Iterator#hasNext hasNext} always returns {@code
4073 * false}.
4074 *
4075 * <li>{@link Iterator#next next} always throws {@link
4076 * NoSuchElementException}.
4077 *
4078 * <li>{@link Iterator#remove remove} always throws {@link
4079 * IllegalStateException}.
4080 *
4081 * </ul>
4082 *
4083 * <p>Implementations of this method are permitted, but not
4084 * required, to return the same object from multiple invocations.
4085 *
4086 * @param <T> type of elements, if there were any, in the iterator
4087 * @return an empty iterator
4088 * @since 1.7
4089 */
4090 @SuppressWarnings("unchecked")
4091 public static <T> Iterator<T> emptyIterator() {
4092 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
4093 }
4094
4095 private static class EmptyIterator<E> implements Iterator<E> {
4096 static final EmptyIterator<Object> EMPTY_ITERATOR
4097 = new EmptyIterator<>();
4098
4099 public boolean hasNext() { return false; }
4100 public E next() { throw new NoSuchElementException(); }
4101 public void remove() { throw new IllegalStateException(); }
4102 @Override
4103 public void forEachRemaining(Consumer<? super E> action) {
4104 Objects.requireNonNull(action);
4105 }
4106 }
4107
4108 /**
4109 * Returns a list iterator that has no elements. More precisely,
4110 *
4111 * <ul compact>
4112 *
4113 * <li>{@link Iterator#hasNext hasNext} and {@link
4114 * ListIterator#hasPrevious hasPrevious} always return {@code
4115 * false}.
4116 *
4117 * <li>{@link Iterator#next next} and {@link ListIterator#previous
4118 * previous} always throw {@link NoSuchElementException}.
4119 *
4120 * <li>{@link Iterator#remove remove} and {@link ListIterator#set
4121 * set} always throw {@link IllegalStateException}.
4122 *
4123 * <li>{@link ListIterator#add add} always throws {@link
4124 * UnsupportedOperationException}.
4125 *
4126 * <li>{@link ListIterator#nextIndex nextIndex} always returns
4127 * {@code 0} .
4128 *
4129 * <li>{@link ListIterator#previousIndex previousIndex} always
4130 * returns {@code -1}.
4131 *
4132 * </ul>
4133 *
4134 * <p>Implementations of this method are permitted, but not
4135 * required, to return the same object from multiple invocations.
4136 *
4137 * @param <T> type of elements, if there were any, in the iterator
4138 * @return an empty list iterator
4139 * @since 1.7
4140 */
4141 @SuppressWarnings("unchecked")
4142 public static <T> ListIterator<T> emptyListIterator() {
4143 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
4144 }
4145
4146 private static class EmptyListIterator<E>
4147 extends EmptyIterator<E>
4148 implements ListIterator<E>
4149 {
4150 static final EmptyListIterator<Object> EMPTY_ITERATOR
4151 = new EmptyListIterator<>();
4152
4153 public boolean hasPrevious() { return false; }
4154 public E previous() { throw new NoSuchElementException(); }
4155 public int nextIndex() { return 0; }
4156 public int previousIndex() { return -1; }
4157 public void set(E e) { throw new IllegalStateException(); }
4158 public void add(E e) { throw new UnsupportedOperationException(); }
4159 }
4160
4161 /**
4162 * Returns an enumeration that has no elements. More precisely,
4163 *
4164 * <ul compact>
4165 *
4166 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
4167 * returns {@code false}.
4168 *
4169 * <li> {@link Enumeration#nextElement nextElement} always throws
4170 * {@link NoSuchElementException}.
4171 *
4172 * </ul>
4173 *
4174 * <p>Implementations of this method are permitted, but not
4175 * required, to return the same object from multiple invocations.
4176 *
4177 * @return an empty enumeration
4178 * @since 1.7
4179 */
4180 @SuppressWarnings("unchecked")
4181 public static <T> Enumeration<T> emptyEnumeration() {
4182 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
4183 }
4184
4185 private static class EmptyEnumeration<E> implements Enumeration<E> {
4186 static final EmptyEnumeration<Object> EMPTY_ENUMERATION
4187 = new EmptyEnumeration<>();
4188
4189 public boolean hasMoreElements() { return false; }
4190 public E nextElement() { throw new NoSuchElementException(); }
4191 }
4192
4193 /**
4194 * The empty set (immutable). This set is serializable.
4195 *
4196 * @see #emptySet()
4197 */
4198 @SuppressWarnings("rawtypes")
4199 public static final Set EMPTY_SET = new EmptySet<>();
4200
4201 /**
4202 * Returns an empty set (immutable). This set is serializable.
4203 * Unlike the like-named field, this method is parameterized.
4204 *
4205 * <p>This example illustrates the type-safe way to obtain an empty set:
4206 * <pre>
4207 * Set<String> s = Collections.emptySet();
4208 * </pre>
4209 * @implNote Implementations of this method need not create a separate
4210 * {@code Set} object for each call. Using this method is likely to have
4211 * comparable cost to using the like-named field. (Unlike this method, the
4212 * field does not provide type safety.)
4213 *
4214 * @return the empty set
4215 *
4216 * @see #EMPTY_SET
4217 * @since 1.5
4218 */
4219 @SuppressWarnings("unchecked")
4220 public static final <T> Set<T> emptySet() {
4221 return (Set<T>) EMPTY_SET;
4222 }
4223
4224 /**
4225 * @serial include
4226 */
4227 private static class EmptySet<E>
4228 extends AbstractSet<E>
4229 implements Serializable
4230 {
4231 private static final long serialVersionUID = 1582296315990362920L;
4232
4233 public Iterator<E> iterator() { return emptyIterator(); }
4234
4235 public int size() {return 0;}
4236 public boolean isEmpty() {return true;}
4237
4238 public boolean contains(Object obj) {return false;}
4239 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4240
4241 public Object[] toArray() { return new Object[0]; }
4242
4243 public <T> T[] toArray(T[] a) {
4244 if (a.length > 0)
4245 a[0] = null;
4246 return a;
4247 }
4248
4249 // Override default methods in Collection
4250 @Override
4251 public void forEach(Consumer<? super E> action) {
4252 Objects.requireNonNull(action);
4253 }
4254 @Override
4255 public boolean removeIf(Predicate<? super E> filter) {
4256 Objects.requireNonNull(filter);
4257 return false;
4258 }
4259 @Override
4260 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4261
4262 // Preserves singleton property
4263 private Object readResolve() {
4264 return EMPTY_SET;
4265 }
4266 }
4267
4268 /**
4269 * Returns an empty sorted set (immutable). This set is serializable.
4270 *
4271 * <p>This example illustrates the type-safe way to obtain an empty
4272 * sorted set:
4273 * <pre> {@code
4274 * SortedSet<String> s = Collections.emptySortedSet();
4275 * }</pre>
4276 *
4277 * @implNote Implementations of this method need not create a separate
4278 * {@code SortedSet} object for each call.
4279 *
4280 * @param <E> type of elements, if there were any, in the set
4281 * @return the empty sorted set
4282 * @since 1.8
4283 */
4284 @SuppressWarnings("unchecked")
4285 public static <E> SortedSet<E> emptySortedSet() {
4286 return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
4287 }
4288
4289 /**
4290 * Returns an empty navigable set (immutable). This set is serializable.
4291 *
4292 * <p>This example illustrates the type-safe way to obtain an empty
4293 * navigable set:
4294 * <pre> {@code
4295 * NavigableSet<String> s = Collections.emptyNavigableSet();
4296 * }</pre>
4297 *
4298 * @implNote Implementations of this method need not
4299 * create a separate {@code NavigableSet} object for each call.
4300 *
4301 * @param <E> type of elements, if there were any, in the set
4302 * @return the empty navigable set
4303 * @since 1.8
4304 */
4305 @SuppressWarnings("unchecked")
4306 public static <E> NavigableSet<E> emptyNavigableSet() {
4307 return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
4308 }
4309
4310 /**
4311 * The empty list (immutable). This list is serializable.
4312 *
4313 * @see #emptyList()
4314 */
4315 @SuppressWarnings("rawtypes")
4316 public static final List EMPTY_LIST = new EmptyList<>();
4317
4318 /**
4319 * Returns an empty list (immutable). This list is serializable.
4320 *
4321 * <p>This example illustrates the type-safe way to obtain an empty list:
4322 * <pre>
4323 * List<String> s = Collections.emptyList();
4324 * </pre>
4325 * Implementation note: Implementations of this method need not
4326 * create a separate <tt>List</tt> object for each call. Using this
4327 * method is likely to have comparable cost to using the like-named
4328 * field. (Unlike this method, the field does not provide type safety.)
4329 *
4330 * @param <T> type of elements, if there were any, in the list
4331 * @return an empty immutable list
4332 *
4333 * @see #EMPTY_LIST
4334 * @since 1.5
4335 */
4336 @SuppressWarnings("unchecked")
4337 public static final <T> List<T> emptyList() {
4338 return (List<T>) EMPTY_LIST;
4339 }
4340
4341 /**
4342 * @serial include
4343 */
4344 private static class EmptyList<E>
4345 extends AbstractList<E>
4346 implements RandomAccess, Serializable {
4347 private static final long serialVersionUID = 8842843931221139166L;
4348
4349 public Iterator<E> iterator() {
4350 return emptyIterator();
4351 }
4352 public ListIterator<E> listIterator() {
4353 return emptyListIterator();
4354 }
4355
4356 public int size() {return 0;}
4357 public boolean isEmpty() {return true;}
4358
4359 public boolean contains(Object obj) {return false;}
4360 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4361
4362 public Object[] toArray() { return new Object[0]; }
4363
4364 public <T> T[] toArray(T[] a) {
4365 if (a.length > 0)
4366 a[0] = null;
4367 return a;
4368 }
4369
4370 public E get(int index) {
4371 throw new IndexOutOfBoundsException("Index: "+index);
4372 }
4373
4374 public boolean equals(Object o) {
4375 return (o instanceof List) && ((List<?>)o).isEmpty();
4376 }
4377
4378 public int hashCode() { return 1; }
4379
4380 @Override
4381 public boolean removeIf(Predicate<? super E> filter) {
4382 Objects.requireNonNull(filter);
4383 return false;
4384 }
4385 @Override
4386 public void replaceAll(UnaryOperator<E> operator) {
4387 Objects.requireNonNull(operator);
4388 }
4389 @Override
4390 public void sort(Comparator<? super E> c) {
4391 Objects.requireNonNull(c);
4392 }
4393
4394 // Override default methods in Collection
4395 @Override
4396 public void forEach(Consumer<? super E> action) {
4397 Objects.requireNonNull(action);
4398 }
4399
4400 @Override
4401 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4402
4403 // Preserves singleton property
4404 private Object readResolve() {
4405 return EMPTY_LIST;
4406 }
4407 }
4408
4409 /**
4410 * The empty map (immutable). This map is serializable.
4411 *
4412 * @see #emptyMap()
4413 * @since 1.3
4414 */
4415 @SuppressWarnings("rawtypes")
4416 public static final Map EMPTY_MAP = new EmptyMap<>();
4417
4418 /**
4419 * Returns an empty map (immutable). This map is serializable.
4420 *
4421 * <p>This example illustrates the type-safe way to obtain an empty map:
4422 * <pre>
4423 * Map<String, Date> s = Collections.emptyMap();
4424 * </pre>
4425 * @implNote Implementations of this method need not create a separate
4426 * {@code Map} object for each call. Using this method is likely to have
4427 * comparable cost to using the like-named field. (Unlike this method, the
4428 * field does not provide type safety.)
4429 *
4430 * @return an empty map
4431 * @see #EMPTY_MAP
4432 * @since 1.5
4433 */
4434 @SuppressWarnings("unchecked")
4435 public static final <K,V> Map<K,V> emptyMap() {
4436 return (Map<K,V>) EMPTY_MAP;
4437 }
4438
4439 /**
4440 * Returns an empty sorted map (immutable). This map is serializable.
4441 *
4442 * <p>This example illustrates the type-safe way to obtain an empty map:
4443 * <pre> {@code
4444 * SortedMap<String, Date> s = Collections.emptySortedMap();
4445 * }</pre>
4446 *
4447 * @implNote Implementations of this method need not create a separate
4448 * {@code SortedMap} object for each call.
4449 *
4450 * @return an empty sorted map
4451 * @since 1.8
4452 */
4453 @SuppressWarnings("unchecked")
4454 public static final <K,V> SortedMap<K,V> emptySortedMap() {
4455 return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
4456 }
4457
4458 /**
4459 * Returns an empty navigable map (immutable). This map is serializable.
4460 *
4461 * <p>This example illustrates the type-safe way to obtain an empty map:
4462 * <pre> {@code
4463 * NavigableMap<String, Date> s = Collections.emptyNavigableMap();
4464 * }</pre>
4465 *
4466 * @implNote Implementations of this method need not create a separate
4467 * {@code NavigableMap} object for each call.
4468 *
4469 * @return an empty navigable map
4470 * @since 1.8
4471 */
4472 @SuppressWarnings("unchecked")
4473 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() {
4474 return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
4475 }
4476
4477 /**
4478 * @serial include
4479 */
4480 private static class EmptyMap<K,V>
4481 extends AbstractMap<K,V>
4482 implements Serializable
4483 {
4484 private static final long serialVersionUID = 6428348081105594320L;
4485
4486 public int size() {return 0;}
4487 public boolean isEmpty() {return true;}
4488 public boolean containsKey(Object key) {return false;}
4489 public boolean containsValue(Object value) {return false;}
4490 public V get(Object key) {return null;}
4491 public Set<K> keySet() {return emptySet();}
4492 public Collection<V> values() {return emptySet();}
4493 public Set<Map.Entry<K,V>> entrySet() {return emptySet();}
4494
4495 public boolean equals(Object o) {
4496 return (o instanceof Map) && ((Map<?,?>)o).isEmpty();
4497 }
4498
4499 public int hashCode() {return 0;}
4500
4501 // Override default methods in Map
4502 @Override
4503 @SuppressWarnings("unchecked")
4504 public V getOrDefault(Object k, V defaultValue) {
4505 return defaultValue;
4506 }
4507
4508 @Override
4509 public void forEach(BiConsumer<? super K, ? super V> action) {
4510 Objects.requireNonNull(action);
4511 }
4512
4513 @Override
4514 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4515 Objects.requireNonNull(function);
4516 }
4517
4518 @Override
4519 public V putIfAbsent(K key, V value) {
4520 throw new UnsupportedOperationException();
4521 }
4522
4523 @Override
4524 public boolean remove(Object key, Object value) {
4525 throw new UnsupportedOperationException();
4526 }
4527
4528 @Override
4529 public boolean replace(K key, V oldValue, V newValue) {
4530 throw new UnsupportedOperationException();
4531 }
4532
4533 @Override
4534 public V replace(K key, V value) {
4535 throw new UnsupportedOperationException();
4536 }
4537
4538 @Override
4539 public V computeIfAbsent(K key,
4540 Function<? super K, ? extends V> mappingFunction) {
4541 throw new UnsupportedOperationException();
4542 }
4543
4544 @Override
4545 public V computeIfPresent(K key,
4546 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4547 throw new UnsupportedOperationException();
4548 }
4549
4550 @Override
4551 public V compute(K key,
4552 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4553 throw new UnsupportedOperationException();
4554 }
4555
4556 @Override
4557 public V merge(K key, V value,
4558 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4559 throw new UnsupportedOperationException();
4560 }
4561
4562 // Preserves singleton property
4563 private Object readResolve() {
4564 return EMPTY_MAP;
4565 }
4566 }
4567
4568 // Singleton collections
4569
4570 /**
4571 * Returns an immutable set containing only the specified object.
4572 * The returned set is serializable.
4573 *
4574 * @param o the sole object to be stored in the returned set.
4575 * @return an immutable set containing only the specified object.
4576 */
4577 public static <T> Set<T> singleton(T o) {
4578 return new SingletonSet<>(o);
4579 }
4580
4581 static <E> Iterator<E> singletonIterator(final E e) {
4582 return new Iterator<E>() {
4583 private boolean hasNext = true;
4584 public boolean hasNext() {
4585 return hasNext;
4586 }
4587 public E next() {
4588 if (hasNext) {
4589 hasNext = false;
4590 return e;
4591 }
4592 throw new NoSuchElementException();
4593 }
4594 public void remove() {
4595 throw new UnsupportedOperationException();
4596 }
4597 @Override
4598 public void forEachRemaining(Consumer<? super E> action) {
4599 Objects.requireNonNull(action);
4600 if (hasNext) {
4601 action.accept(e);
4602 hasNext = false;
4603 }
4604 }
4605 };
4606 }
4607
4608 /**
4609 * Creates a {@code Spliterator} with only the specified element
4610 *
4611 * @param <T> Type of elements
4612 * @return A singleton {@code Spliterator}
4613 */
4614 static <T> Spliterator<T> singletonSpliterator(final T element) {
4615 return new Spliterator<T>() {
4616 long est = 1;
4617
4618 @Override
4619 public Spliterator<T> trySplit() {
4620 return null;
4621 }
4622
4623 @Override
4624 public boolean tryAdvance(Consumer<? super T> consumer) {
4625 Objects.requireNonNull(consumer);
4626 if (est > 0) {
4627 est--;
4628 consumer.accept(element);
4629 return true;
4630 }
4631 return false;
4632 }
4633
4634 @Override
4635 public void forEachRemaining(Consumer<? super T> consumer) {
4636 tryAdvance(consumer);
4637 }
4638
4639 @Override
4640 public long estimateSize() {
4641 return est;
4642 }
4643
4644 @Override
4645 public int characteristics() {
4646 int value = (element != null) ? Spliterator.NONNULL : 0;
4647
4648 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE |
4649 Spliterator.DISTINCT | Spliterator.ORDERED;
4650 }
4651 };
4652 }
4653
4654 /**
4655 * @serial include
4656 */
4657 private static class SingletonSet<E>
4658 extends AbstractSet<E>
4659 implements Serializable
4660 {
4661 private static final long serialVersionUID = 3193687207550431679L;
4662
4663 private final E element;
4664
4665 SingletonSet(E e) {element = e;}
4666
4667 public Iterator<E> iterator() {
4668 return singletonIterator(element);
4669 }
4670
4671 public int size() {return 1;}
4672
4673 public boolean contains(Object o) {return eq(o, element);}
4674
4675 // Override default methods for Collection
4676 @Override
4677 public void forEach(Consumer<? super E> action) {
4678 action.accept(element);
4679 }
4680 @Override
4681 public Spliterator<E> spliterator() {
4682 return singletonSpliterator(element);
4683 }
4684 @Override
4685 public boolean removeIf(Predicate<? super E> filter) {
4686 throw new UnsupportedOperationException();
4687 }
4688 }
4689
4690 /**
4691 * Returns an immutable list containing only the specified object.
4692 * The returned list is serializable.
4693 *
4694 * @param o the sole object to be stored in the returned list.
4695 * @return an immutable list containing only the specified object.
4696 * @since 1.3
4697 */
4698 public static <T> List<T> singletonList(T o) {
4699 return new SingletonList<>(o);
4700 }
4701
4702 /**
4703 * @serial include
4704 */
4705 private static class SingletonList<E>
4706 extends AbstractList<E>
4707 implements RandomAccess, Serializable {
4708
4709 private static final long serialVersionUID = 3093736618740652951L;
4710
4711 private final E element;
4712
4713 SingletonList(E obj) {element = obj;}
4714
4715 public Iterator<E> iterator() {
4716 return singletonIterator(element);
4717 }
4718
4719 public int size() {return 1;}
4720
4721 public boolean contains(Object obj) {return eq(obj, element);}
4722
4723 public E get(int index) {
4724 if (index != 0)
4725 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
4726 return element;
4727 }
4728
4729 // Override default methods for Collection
4730 @Override
4731 public void forEach(Consumer<? super E> action) {
4732 action.accept(element);
4733 }
4734 @Override
4735 public boolean removeIf(Predicate<? super E> filter) {
4736 throw new UnsupportedOperationException();
4737 }
4738 @Override
4739 public void replaceAll(UnaryOperator<E> operator) {
4740 throw new UnsupportedOperationException();
4741 }
4742 @Override
4743 public void sort(Comparator<? super E> c) {
4744 }
4745 @Override
4746 public Spliterator<E> spliterator() {
4747 return singletonSpliterator(element);
4748 }
4749 }
4750
4751 /**
4752 * Returns an immutable map, mapping only the specified key to the
4753 * specified value. The returned map is serializable.
4754 *
4755 * @param key the sole key to be stored in the returned map.
4756 * @param value the value to which the returned map maps <tt>key</tt>.
4757 * @return an immutable map containing only the specified key-value
4758 * mapping.
4759 * @since 1.3
4760 */
4761 public static <K,V> Map<K,V> singletonMap(K key, V value) {
4762 return new SingletonMap<>(key, value);
4763 }
4764
4765 /**
4766 * @serial include
4767 */
4768 private static class SingletonMap<K,V>
4769 extends AbstractMap<K,V>
4770 implements Serializable {
4771 private static final long serialVersionUID = -6979724477215052911L;
4772
4773 private final K k;
4774 private final V v;
4775
4776 SingletonMap(K key, V value) {
4777 k = key;
4778 v = value;
4779 }
4780
4781 public int size() {return 1;}
4782 public boolean isEmpty() {return false;}
4783 public boolean containsKey(Object key) {return eq(key, k);}
4784 public boolean containsValue(Object value) {return eq(value, v);}
4785 public V get(Object key) {return (eq(key, k) ? v : null);}
4786
4787 private transient Set<K> keySet = null;
4788 private transient Set<Map.Entry<K,V>> entrySet = null;
4789 private transient Collection<V> values = null;
4790
4791 public Set<K> keySet() {
4792 if (keySet==null)
4793 keySet = singleton(k);
4794 return keySet;
4795 }
4796
4797 public Set<Map.Entry<K,V>> entrySet() {
4798 if (entrySet==null)
4799 entrySet = Collections.<Map.Entry<K,V>>singleton(
4800 new SimpleImmutableEntry<>(k, v));
4801 return entrySet;
4802 }
4803
4804 public Collection<V> values() {
4805 if (values==null)
4806 values = singleton(v);
4807 return values;
4808 }
4809
4810 // Override default methods in Map
4811 @Override
4812 public V getOrDefault(Object key, V defaultValue) {
4813 return eq(key, k) ? v : defaultValue;
4814 }
4815
4816 @Override
4817 public void forEach(BiConsumer<? super K, ? super V> action) {
4818 action.accept(k, v);
4819 }
4820
4821 @Override
4822 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4823 throw new UnsupportedOperationException();
4824 }
4825
4826 @Override
4827 public V putIfAbsent(K key, V value) {
4828 throw new UnsupportedOperationException();
4829 }
4830
4831 @Override
4832 public boolean remove(Object key, Object value) {
4833 throw new UnsupportedOperationException();
4834 }
4835
4836 @Override
4837 public boolean replace(K key, V oldValue, V newValue) {
4838 throw new UnsupportedOperationException();
4839 }
4840
4841 @Override
4842 public V replace(K key, V value) {
4843 throw new UnsupportedOperationException();
4844 }
4845
4846 @Override
4847 public V computeIfAbsent(K key,
4848 Function<? super K, ? extends V> mappingFunction) {
4849 throw new UnsupportedOperationException();
4850 }
4851
4852 @Override
4853 public V computeIfPresent(K key,
4854 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4855 throw new UnsupportedOperationException();
4856 }
4857
4858 @Override
4859 public V compute(K key,
4860 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4861 throw new UnsupportedOperationException();
4862 }
4863
4864 @Override
4865 public V merge(K key, V value,
4866 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4867 throw new UnsupportedOperationException();
4868 }
4869 }
4870
4871 // Miscellaneous
4872
4873 /**
4874 * Returns an immutable list consisting of <tt>n</tt> copies of the
4875 * specified object. The newly allocated data object is tiny (it contains
4876 * a single reference to the data object). This method is useful in
4877 * combination with the <tt>List.addAll</tt> method to grow lists.
4878 * The returned list is serializable.
4879 *
4880 * @param n the number of elements in the returned list.
4881 * @param o the element to appear repeatedly in the returned list.
4882 * @return an immutable list consisting of <tt>n</tt> copies of the
4883 * specified object.
4884 * @throws IllegalArgumentException if {@code n < 0}
4885 * @see List#addAll(Collection)
4886 * @see List#addAll(int, Collection)
4887 */
4888 public static <T> List<T> nCopies(int n, T o) {
4889 if (n < 0)
4890 throw new IllegalArgumentException("List length = " + n);
4891 return new CopiesList<>(n, o);
4892 }
4893
4894 /**
4895 * @serial include
4896 */
4897 private static class CopiesList<E>
4898 extends AbstractList<E>
4899 implements RandomAccess, Serializable
4900 {
4901 private static final long serialVersionUID = 2739099268398711800L;
4902
4903 final int n;
4904 final E element;
4905
4906 CopiesList(int n, E e) {
4907 assert n >= 0;
4908 this.n = n;
4909 element = e;
4910 }
4911
4912 public int size() {
4913 return n;
4914 }
4915
4916 public boolean contains(Object obj) {
4917 return n != 0 && eq(obj, element);
4918 }
4919
4920 public int indexOf(Object o) {
4921 return contains(o) ? 0 : -1;
4922 }
4923
4924 public int lastIndexOf(Object o) {
4925 return contains(o) ? n - 1 : -1;
4926 }
4927
4928 public E get(int index) {
4929 if (index < 0 || index >= n)
4930 throw new IndexOutOfBoundsException("Index: "+index+
4931 ", Size: "+n);
4932 return element;
4933 }
4934
4935 public Object[] toArray() {
4936 final Object[] a = new Object[n];
4937 if (element != null)
4938 Arrays.fill(a, 0, n, element);
4939 return a;
4940 }
4941
4942 @SuppressWarnings("unchecked")
4943 public <T> T[] toArray(T[] a) {
4944 final int n = this.n;
4945 if (a.length < n) {
4946 a = (T[])java.lang.reflect.Array
4947 .newInstance(a.getClass().getComponentType(), n);
4948 if (element != null)
4949 Arrays.fill(a, 0, n, element);
4950 } else {
4951 Arrays.fill(a, 0, n, element);
4952 if (a.length > n)
4953 a[n] = null;
4954 }
4955 return a;
4956 }
4957
4958 public List<E> subList(int fromIndex, int toIndex) {
4959 if (fromIndex < 0)
4960 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
4961 if (toIndex > n)
4962 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
4963 if (fromIndex > toIndex)
4964 throw new IllegalArgumentException("fromIndex(" + fromIndex +
4965 ") > toIndex(" + toIndex + ")");
4966 return new CopiesList<>(toIndex - fromIndex, element);
4967 }
4968 }
4969
4970 /**
4971 * Returns a comparator that imposes the reverse of the <em>natural
4972 * ordering</em> on a collection of objects that implement the
4973 * {@code Comparable} interface. (The natural ordering is the ordering
4974 * imposed by the objects' own {@code compareTo} method.) This enables a
4975 * simple idiom for sorting (or maintaining) collections (or arrays) of
4976 * objects that implement the {@code Comparable} interface in
4977 * reverse-natural-order. For example, suppose {@code a} is an array of
4978 * strings. Then: <pre>
4979 * Arrays.sort(a, Collections.reverseOrder());
4980 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
4981 *
4982 * The returned comparator is serializable.
4983 *
4984 * @return A comparator that imposes the reverse of the <i>natural
4985 * ordering</i> on a collection of objects that implement
4986 * the <tt>Comparable</tt> interface.
4987 * @see Comparable
4988 */
4989 @SuppressWarnings("unchecked")
4990 public static <T> Comparator<T> reverseOrder() {
4991 return (Comparator<T>) ReverseComparator.REVERSE_ORDER;
4992 }
4993
4994 /**
4995 * @serial include
4996 */
4997 private static class ReverseComparator
4998 implements Comparator<Comparable<Object>>, Serializable {
4999
5000 private static final long serialVersionUID = 7207038068494060240L;
5001
5002 static final ReverseComparator REVERSE_ORDER
5003 = new ReverseComparator();
5004
5005 public int compare(Comparable<Object> c1, Comparable<Object> c2) {
5006 return c2.compareTo(c1);
5007 }
5008
5009 private Object readResolve() { return Collections.reverseOrder(); }
5010 }
5011
5012 /**
5013 * Returns a comparator that imposes the reverse ordering of the specified
5014 * comparator. If the specified comparator is {@code null}, this method is
5015 * equivalent to {@link #reverseOrder()} (in other words, it returns a
5016 * comparator that imposes the reverse of the <em>natural ordering</em> on
5017 * a collection of objects that implement the Comparable interface).
5018 *
5019 * <p>The returned comparator is serializable (assuming the specified
5020 * comparator is also serializable or {@code null}).
5021 *
5022 * @param cmp a comparator who's ordering is to be reversed by the returned
5023 * comparator or {@code null}
5024 * @return A comparator that imposes the reverse ordering of the
5025 * specified comparator.
5026 * @since 1.5
5027 */
5028 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
5029 if (cmp == null)
5030 return reverseOrder();
5031
5032 if (cmp instanceof ReverseComparator2)
5033 return ((ReverseComparator2<T>)cmp).cmp;
5034
5035 return new ReverseComparator2<>(cmp);
5036 }
5037
5038 /**
5039 * @serial include
5040 */
5041 private static class ReverseComparator2<T> implements Comparator<T>,
5042 Serializable
5043 {
5044 private static final long serialVersionUID = 4374092139857L;
5045
5046 /**
5047 * The comparator specified in the static factory. This will never
5048 * be null, as the static factory returns a ReverseComparator
5049 * instance if its argument is null.
5050 *
5051 * @serial
5052 */
5053 final Comparator<T> cmp;
5054
5055 ReverseComparator2(Comparator<T> cmp) {
5056 assert cmp != null;
5057 this.cmp = cmp;
5058 }
5059
5060 public int compare(T t1, T t2) {
5061 return cmp.compare(t2, t1);
5062 }
5063
5064 public boolean equals(Object o) {
5065 return (o == this) ||
5066 (o instanceof ReverseComparator2 &&
5067 cmp.equals(((ReverseComparator2)o).cmp));
5068 }
5069
5070 public int hashCode() {
5071 return cmp.hashCode() ^ Integer.MIN_VALUE;
5072 }
5073 }
5074
5075 /**
5076 * Returns an enumeration over the specified collection. This provides
5077 * interoperability with legacy APIs that require an enumeration
5078 * as input.
5079 *
5080 * @param c the collection for which an enumeration is to be returned.
5081 * @return an enumeration over the specified collection.
5082 * @see Enumeration
5083 */
5084 public static <T> Enumeration<T> enumeration(final Collection<T> c) {
5085 return new Enumeration<T>() {
5086 private final Iterator<T> i = c.iterator();
5087
5088 public boolean hasMoreElements() {
5089 return i.hasNext();
5090 }
5091
5092 public T nextElement() {
5093 return i.next();
5094 }
5095 };
5096 }
5097
5098 /**
5099 * Returns an array list containing the elements returned by the
5100 * specified enumeration in the order they are returned by the
5101 * enumeration. This method provides interoperability between
5102 * legacy APIs that return enumerations and new APIs that require
5103 * collections.
5104 *
5105 * @param e enumeration providing elements for the returned
5106 * array list
5107 * @return an array list containing the elements returned
5108 * by the specified enumeration.
5109 * @since 1.4
5110 * @see Enumeration
5111 * @see ArrayList
5112 */
5113 public static <T> ArrayList<T> list(Enumeration<T> e) {
5114 ArrayList<T> l = new ArrayList<>();
5115 while (e.hasMoreElements())
5116 l.add(e.nextElement());
5117 return l;
5118 }
5119
5120 /**
5121 * Returns true if the specified arguments are equal, or both null.
5122 *
5123 * NB: Do not replace with Object.equals until JDK-8015417 is resolved.
5124 */
5125 static boolean eq(Object o1, Object o2) {
5126 return o1==null ? o2==null : o1.equals(o2);
5127 }
5128
5129 /**
5130 * Returns the number of elements in the specified collection equal to the
5131 * specified object. More formally, returns the number of elements
5132 * <tt>e</tt> in the collection such that
5133 * <tt>(o == null ? e == null : o.equals(e))</tt>.
5134 *
5135 * @param c the collection in which to determine the frequency
5136 * of <tt>o</tt>
5137 * @param o the object whose frequency is to be determined
5138 * @throws NullPointerException if <tt>c</tt> is null
5139 * @since 1.5
5140 */
5141 public static int frequency(Collection<?> c, Object o) {
5142 int result = 0;
5143 if (o == null) {
5144 for (Object e : c)
5145 if (e == null)
5146 result++;
5147 } else {
5148 for (Object e : c)
5149 if (o.equals(e))
5150 result++;
5151 }
5152 return result;
5153 }
5154
5155 /**
5156 * Returns {@code true} if the two specified collections have no
5157 * elements in common.
5158 *
5159 * <p>Care must be exercised if this method is used on collections that
5160 * do not comply with the general contract for {@code Collection}.
5161 * Implementations may elect to iterate over either collection and test
5162 * for containment in the other collection (or to perform any equivalent
5163 * computation). If either collection uses a nonstandard equality test
5164 * (as does a {@link SortedSet} whose ordering is not <em>compatible with
5165 * equals</em>, or the key set of an {@link IdentityHashMap}), both
5166 * collections must use the same nonstandard equality test, or the
5167 * result of this method is undefined.
5168 *
5169 * <p>Care must also be exercised when using collections that have
5170 * restrictions on the elements that they may contain. Collection
5171 * implementations are allowed to throw exceptions for any operation
5172 * involving elements they deem ineligible. For absolute safety the
5173 * specified collections should contain only elements which are
5174 * eligible elements for both collections.
5175 *
5176 * <p>Note that it is permissible to pass the same collection in both
5177 * parameters, in which case the method will return {@code true} if and
5178 * only if the collection is empty.
5179 *
5180 * @param c1 a collection
5181 * @param c2 a collection
5182 * @return {@code true} if the two specified collections have no
5183 * elements in common.
5184 * @throws NullPointerException if either collection is {@code null}.
5185 * @throws NullPointerException if one collection contains a {@code null}
5186 * element and {@code null} is not an eligible element for the other collection.
5187 * (<a href="Collection.html#optional-restrictions">optional</a>)
5188 * @throws ClassCastException if one collection contains an element that is
5189 * of a type which is ineligible for the other collection.
5190 * (<a href="Collection.html#optional-restrictions">optional</a>)
5191 * @since 1.5
5192 */
5193 public static boolean disjoint(Collection<?> c1, Collection<?> c2) {
5194 // The collection to be used for contains(). Preference is given to
5195 // the collection who's contains() has lower O() complexity.
5196 Collection<?> contains = c2;
5197 // The collection to be iterated. If the collections' contains() impl
5198 // are of different O() complexity, the collection with slower
5199 // contains() will be used for iteration. For collections who's
5200 // contains() are of the same complexity then best performance is
5201 // achieved by iterating the smaller collection.
5202 Collection<?> iterate = c1;
5203
5204 // Performance optimization cases. The heuristics:
5205 // 1. Generally iterate over c1.
5206 // 2. If c1 is a Set then iterate over c2.
5207 // 3. If either collection is empty then result is always true.
5208 // 4. Iterate over the smaller Collection.
5209 if (c1 instanceof Set) {
5210 // Use c1 for contains as a Set's contains() is expected to perform
5211 // better than O(N/2)
5212 iterate = c2;
5213 contains = c1;
5214 } else if (!(c2 instanceof Set)) {
5215 // Both are mere Collections. Iterate over smaller collection.
5216 // Example: If c1 contains 3 elements and c2 contains 50 elements and
5217 // assuming contains() requires ceiling(N/2) comparisons then
5218 // checking for all c1 elements in c2 would require 75 comparisons
5219 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring
5220 // 100 comparisons (50 * ceiling(3/2)).
5221 int c1size = c1.size();
5222 int c2size = c2.size();
5223 if (c1size == 0 || c2size == 0) {
5224 // At least one collection is empty. Nothing will match.
5225 return true;
5226 }
5227
5228 if (c1size > c2size) {
5229 iterate = c2;
5230 contains = c1;
5231 }
5232 }
5233
5234 for (Object e : iterate) {
5235 if (contains.contains(e)) {
5236 // Found a common element. Collections are not disjoint.
5237 return false;
5238 }
5239 }
5240
5241 // No common elements were found.
5242 return true;
5243 }
5244
5245 /**
5246 * Adds all of the specified elements to the specified collection.
5247 * Elements to be added may be specified individually or as an array.
5248 * The behavior of this convenience method is identical to that of
5249 * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely
5250 * to run significantly faster under most implementations.
5251 *
5252 * <p>When elements are specified individually, this method provides a
5253 * convenient way to add a few elements to an existing collection:
5254 * <pre>
5255 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
5256 * </pre>
5257 *
5258 * @param c the collection into which <tt>elements</tt> are to be inserted
5259 * @param elements the elements to insert into <tt>c</tt>
5260 * @return <tt>true</tt> if the collection changed as a result of the call
5261 * @throws UnsupportedOperationException if <tt>c</tt> does not support
5262 * the <tt>add</tt> operation
5263 * @throws NullPointerException if <tt>elements</tt> contains one or more
5264 * null values and <tt>c</tt> does not permit null elements, or
5265 * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt>
5266 * @throws IllegalArgumentException if some property of a value in
5267 * <tt>elements</tt> prevents it from being added to <tt>c</tt>
5268 * @see Collection#addAll(Collection)
5269 * @since 1.5
5270 */
5271 @SafeVarargs
5272 public static <T> boolean addAll(Collection<? super T> c, T... elements) {
5273 boolean result = false;
5274 for (T element : elements)
5275 result |= c.add(element);
5276 return result;
5277 }
5278
5279 /**
5280 * Returns a set backed by the specified map. The resulting set displays
5281 * the same ordering, concurrency, and performance characteristics as the
5282 * backing map. In essence, this factory method provides a {@link Set}
5283 * implementation corresponding to any {@link Map} implementation. There
5284 * is no need to use this method on a {@link Map} implementation that
5285 * already has a corresponding {@link Set} implementation (such as {@link
5286 * HashMap} or {@link TreeMap}).
5287 *
5288 * <p>Each method invocation on the set returned by this method results in
5289 * exactly one method invocation on the backing map or its <tt>keySet</tt>
5290 * view, with one exception. The <tt>addAll</tt> method is implemented
5291 * as a sequence of <tt>put</tt> invocations on the backing map.
5292 *
5293 * <p>The specified map must be empty at the time this method is invoked,
5294 * and should not be accessed directly after this method returns. These
5295 * conditions are ensured if the map is created empty, passed directly
5296 * to this method, and no reference to the map is retained, as illustrated
5297 * in the following code fragment:
5298 * <pre>
5299 * Set<Object> weakHashSet = Collections.newSetFromMap(
5300 * new WeakHashMap<Object, Boolean>());
5301 * </pre>
5302 *
5303 * @param map the backing map
5304 * @return the set backed by the map
5305 * @throws IllegalArgumentException if <tt>map</tt> is not empty
5306 * @since 1.6
5307 */
5308 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
5309 return new SetFromMap<>(map);
5310 }
5311
5312 /**
5313 * @serial include
5314 */
5315 private static class SetFromMap<E> extends AbstractSet<E>
5316 implements Set<E>, Serializable
5317 {
5318 private final Map<E, Boolean> m; // The backing map
5319 private transient Set<E> s; // Its keySet
5320
5321 SetFromMap(Map<E, Boolean> map) {
5322 if (!map.isEmpty())
5323 throw new IllegalArgumentException("Map is non-empty");
5324 m = map;
5325 s = map.keySet();
5326 }
5327
5328 public void clear() { m.clear(); }
5329 public int size() { return m.size(); }
5330 public boolean isEmpty() { return m.isEmpty(); }
5331 public boolean contains(Object o) { return m.containsKey(o); }
5332 public boolean remove(Object o) { return m.remove(o) != null; }
5333 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
5334 public Iterator<E> iterator() { return s.iterator(); }
5335 public Object[] toArray() { return s.toArray(); }
5336 public <T> T[] toArray(T[] a) { return s.toArray(a); }
5337 public String toString() { return s.toString(); }
5338 public int hashCode() { return s.hashCode(); }
5339 public boolean equals(Object o) { return o == this || s.equals(o); }
5340 public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
5341 public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
5342 public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
5343 // addAll is the only inherited implementation
5344
5345 // Override default methods in Collection
5346 @Override
5347 public void forEach(Consumer<? super E> action) {
5348 s.forEach(action);
5349 }
5350 @Override
5351 public boolean removeIf(Predicate<? super E> filter) {
5352 return s.removeIf(filter);
5353 }
5354
5355 @Override
5356 public Spliterator<E> spliterator() {return s.spliterator();}
5357
5358 private static final long serialVersionUID = 2454657854757543876L;
5359
5360 private void readObject(java.io.ObjectInputStream stream)
5361 throws IOException, ClassNotFoundException
5362 {
5363 stream.defaultReadObject();
5364 s = m.keySet();
5365 }
5366 }
5367
5368 /**
5369 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
5370 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>,
5371 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This
5372 * view can be useful when you would like to use a method
5373 * requiring a <tt>Queue</tt> but you need Lifo ordering.
5374 *
5375 * <p>Each method invocation on the queue returned by this method
5376 * results in exactly one method invocation on the backing deque, with
5377 * one exception. The {@link Queue#addAll addAll} method is
5378 * implemented as a sequence of {@link Deque#addFirst addFirst}
5379 * invocations on the backing deque.
5380 *
5381 * @param deque the deque
5382 * @return the queue
5383 * @since 1.6
5384 */
5385 public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
5386 return new AsLIFOQueue<>(deque);
5387 }
5388
5389 /**
5390 * @serial include
5391 */
5392 static class AsLIFOQueue<E> extends AbstractQueue<E>
5393 implements Queue<E>, Serializable {
5394 private static final long serialVersionUID = 1802017725587941708L;
5395 private final Deque<E> q;
5396 AsLIFOQueue(Deque<E> q) { this.q = q; }
5397 public boolean add(E e) { q.addFirst(e); return true; }
5398 public boolean offer(E e) { return q.offerFirst(e); }
5399 public E poll() { return q.pollFirst(); }
5400 public E remove() { return q.removeFirst(); }
5401 public E peek() { return q.peekFirst(); }
5402 public E element() { return q.getFirst(); }
5403 public void clear() { q.clear(); }
5404 public int size() { return q.size(); }
5405 public boolean isEmpty() { return q.isEmpty(); }
5406 public boolean contains(Object o) { return q.contains(o); }
5407 public boolean remove(Object o) { return q.remove(o); }
5408 public Iterator<E> iterator() { return q.iterator(); }
5409 public Object[] toArray() { return q.toArray(); }
5410 public <T> T[] toArray(T[] a) { return q.toArray(a); }
5411 public String toString() { return q.toString(); }
5412 public boolean containsAll(Collection<?> c) {return q.containsAll(c);}
5413 public boolean removeAll(Collection<?> c) {return q.removeAll(c);}
5414 public boolean retainAll(Collection<?> c) {return q.retainAll(c);}
5415 // We use inherited addAll; forwarding addAll would be wrong
5416
5417 // Override default methods in Collection
5418 @Override
5419 public void forEach(Consumer<? super E> action) {q.forEach(action);}
5420 @Override
5421 public Spliterator<E> spliterator() {return q.spliterator();}
5422 @Override
5423 public boolean removeIf(Predicate<? super E> filter) {
5424 return q.removeIf(filter);
5425 }
5426 }
5427 }