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