1 /*
2 * Copyright (c) 1997, 2017, 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}/java/util/package-summary.html#CollectionsFramework">
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 <a href="Collection.html#unmodview">unmodifiable view</a> of the
993 * specified collection. Query operations on the returned collection "read through"
994 * to the specified collection, and attempts to modify the returned
995 * collection, whether direct or via its iterator, result in an
996 * {@code UnsupportedOperationException}.<p>
997 *
998 * The returned collection does <i>not</i> pass the hashCode and equals
999 * operations through to the backing collection, but relies on
1000 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
1001 * is necessary to preserve the contracts of these operations in the case
1002 * that the backing collection is a set or a list.<p>
1003 *
1004 * The returned collection will be serializable if the specified collection
1005 * is serializable.
1006 *
1007 * @param <T> the class of the objects in the collection
1008 * @param c the collection for which an unmodifiable view is to be
1009 * returned.
1010 * @return an unmodifiable view of the specified collection.
1011 */
1012 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) {
1013 return new UnmodifiableCollection<>(c);
1014 }
1015
1016 /**
1017 * @serial include
1018 */
1019 static class UnmodifiableCollection<E> implements Collection<E>, Serializable {
1020 private static final long serialVersionUID = 1820017752578914078L;
1021
1022 final Collection<? extends E> c;
1023
1024 UnmodifiableCollection(Collection<? extends E> c) {
1025 if (c==null)
1026 throw new NullPointerException();
1027 this.c = c;
1028 }
1029
1030 public int size() {return c.size();}
1031 public boolean isEmpty() {return c.isEmpty();}
1032 public boolean contains(Object o) {return c.contains(o);}
1033 public Object[] toArray() {return c.toArray();}
1034 public <T> T[] toArray(T[] a) {return c.toArray(a);}
1035 public String toString() {return c.toString();}
1036
1037 public Iterator<E> iterator() {
1038 return new Iterator<E>() {
1039 private final Iterator<? extends E> i = c.iterator();
1040
1041 public boolean hasNext() {return i.hasNext();}
1042 public E next() {return i.next();}
1043 public void remove() {
1044 throw new UnsupportedOperationException();
1045 }
1046 @Override
1047 public void forEachRemaining(Consumer<? super E> action) {
1048 // Use backing collection version
1049 i.forEachRemaining(action);
1050 }
1051 };
1052 }
1053
1054 public boolean add(E e) {
1055 throw new UnsupportedOperationException();
1056 }
1057 public boolean remove(Object o) {
1058 throw new UnsupportedOperationException();
1059 }
1060
1061 public boolean containsAll(Collection<?> coll) {
1062 return c.containsAll(coll);
1063 }
1064 public boolean addAll(Collection<? extends E> coll) {
1065 throw new UnsupportedOperationException();
1066 }
1067 public boolean removeAll(Collection<?> coll) {
1068 throw new UnsupportedOperationException();
1069 }
1070 public boolean retainAll(Collection<?> coll) {
1071 throw new UnsupportedOperationException();
1072 }
1073 public void clear() {
1074 throw new UnsupportedOperationException();
1075 }
1076
1077 // Override default methods in Collection
1078 @Override
1079 public void forEach(Consumer<? super E> action) {
1080 c.forEach(action);
1081 }
1082 @Override
1083 public boolean removeIf(Predicate<? super E> filter) {
1084 throw new UnsupportedOperationException();
1085 }
1086 @SuppressWarnings("unchecked")
1087 @Override
1088 public Spliterator<E> spliterator() {
1089 return (Spliterator<E>)c.spliterator();
1090 }
1091 @SuppressWarnings("unchecked")
1092 @Override
1093 public Stream<E> stream() {
1094 return (Stream<E>)c.stream();
1095 }
1096 @SuppressWarnings("unchecked")
1097 @Override
1098 public Stream<E> parallelStream() {
1099 return (Stream<E>)c.parallelStream();
1100 }
1101 }
1102
1103 /**
1104 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1105 * specified set. Query operations on the returned set "read through" to the specified
1106 * set, and attempts to modify the returned set, whether direct or via its
1107 * iterator, result in an {@code UnsupportedOperationException}.<p>
1108 *
1109 * The returned set will be serializable if the specified set
1110 * is serializable.
1111 *
1112 * @param <T> the class of the objects in the set
1113 * @param s the set for which an unmodifiable view is to be returned.
1114 * @return an unmodifiable view of the specified set.
1115 */
1116 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
1117 return new UnmodifiableSet<>(s);
1118 }
1119
1120 /**
1121 * @serial include
1122 */
1123 static class UnmodifiableSet<E> extends UnmodifiableCollection<E>
1124 implements Set<E>, Serializable {
1125 private static final long serialVersionUID = -9215047833775013803L;
1126
1127 UnmodifiableSet(Set<? extends E> s) {super(s);}
1128 public boolean equals(Object o) {return o == this || c.equals(o);}
1129 public int hashCode() {return c.hashCode();}
1130 }
1131
1132 /**
1133 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1134 * specified sorted set. Query operations on the returned sorted set "read
1135 * through" to the specified sorted set. Attempts to modify the returned
1136 * sorted set, whether direct, via its iterator, or via its
1137 * {@code subSet}, {@code headSet}, or {@code tailSet} views, result in
1138 * an {@code UnsupportedOperationException}.<p>
1139 *
1140 * The returned sorted set will be serializable if the specified sorted set
1141 * is serializable.
1142 *
1143 * @param <T> the class of the objects in the set
1144 * @param s the sorted set for which an unmodifiable view is to be
1145 * returned.
1146 * @return an unmodifiable view of the specified sorted set.
1147 */
1148 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) {
1149 return new UnmodifiableSortedSet<>(s);
1150 }
1151
1152 /**
1153 * @serial include
1154 */
1155 static class UnmodifiableSortedSet<E>
1156 extends UnmodifiableSet<E>
1157 implements SortedSet<E>, Serializable {
1158 private static final long serialVersionUID = -4929149591599911165L;
1159 private final SortedSet<E> ss;
1160
1161 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;}
1162
1163 public Comparator<? super E> comparator() {return ss.comparator();}
1164
1165 public SortedSet<E> subSet(E fromElement, E toElement) {
1166 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement));
1167 }
1168 public SortedSet<E> headSet(E toElement) {
1169 return new UnmodifiableSortedSet<>(ss.headSet(toElement));
1170 }
1171 public SortedSet<E> tailSet(E fromElement) {
1172 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement));
1173 }
1174
1175 public E first() {return ss.first();}
1176 public E last() {return ss.last();}
1177 }
1178
1179 /**
1180 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1181 * specified navigable set. Query operations on the returned navigable set "read
1182 * through" to the specified navigable set. Attempts to modify the returned
1183 * navigable set, whether direct, via its iterator, or via its
1184 * {@code subSet}, {@code headSet}, or {@code tailSet} views, result in
1185 * an {@code UnsupportedOperationException}.<p>
1186 *
1187 * The returned navigable set will be serializable if the specified
1188 * navigable set is serializable.
1189 *
1190 * @param <T> the class of the objects in the set
1191 * @param s the navigable set for which an unmodifiable view is to be
1192 * returned
1193 * @return an unmodifiable view of the specified navigable set
1194 * @since 1.8
1195 */
1196 public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) {
1197 return new UnmodifiableNavigableSet<>(s);
1198 }
1199
1200 /**
1201 * Wraps a navigable set and disables all of the mutative operations.
1202 *
1203 * @param <E> type of elements
1204 * @serial include
1205 */
1206 static class UnmodifiableNavigableSet<E>
1207 extends UnmodifiableSortedSet<E>
1208 implements NavigableSet<E>, Serializable {
1209
1210 private static final long serialVersionUID = -6027448201786391929L;
1211
1212 /**
1213 * A singleton empty unmodifiable navigable set used for
1214 * {@link #emptyNavigableSet()}.
1215 *
1216 * @param <E> type of elements, if there were any, and bounds
1217 */
1218 private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E>
1219 implements Serializable {
1220 private static final long serialVersionUID = -6291252904449939134L;
1221
1222 public EmptyNavigableSet() {
1223 super(new TreeSet<>());
1224 }
1225
1226 private Object readResolve() { return EMPTY_NAVIGABLE_SET; }
1227 }
1228
1229 @SuppressWarnings("rawtypes")
1230 private static final NavigableSet<?> EMPTY_NAVIGABLE_SET =
1231 new EmptyNavigableSet<>();
1232
1233 /**
1234 * The instance we are protecting.
1235 */
1236 private final NavigableSet<E> ns;
1237
1238 UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;}
1239
1240 public E lower(E e) { return ns.lower(e); }
1241 public E floor(E e) { return ns.floor(e); }
1242 public E ceiling(E e) { return ns.ceiling(e); }
1243 public E higher(E e) { return ns.higher(e); }
1244 public E pollFirst() { throw new UnsupportedOperationException(); }
1245 public E pollLast() { throw new UnsupportedOperationException(); }
1246 public NavigableSet<E> descendingSet()
1247 { return new UnmodifiableNavigableSet<>(ns.descendingSet()); }
1248 public Iterator<E> descendingIterator()
1249 { return descendingSet().iterator(); }
1250
1251 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
1252 return new UnmodifiableNavigableSet<>(
1253 ns.subSet(fromElement, fromInclusive, toElement, toInclusive));
1254 }
1255
1256 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
1257 return new UnmodifiableNavigableSet<>(
1258 ns.headSet(toElement, inclusive));
1259 }
1260
1261 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
1262 return new UnmodifiableNavigableSet<>(
1263 ns.tailSet(fromElement, inclusive));
1264 }
1265 }
1266
1267 /**
1268 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1269 * specified list. Query operations on the returned list "read through" to the
1270 * specified list, and attempts to modify the returned list, whether
1271 * direct or via its iterator, result in an
1272 * {@code UnsupportedOperationException}.<p>
1273 *
1274 * The returned list will be serializable if the specified list
1275 * is serializable. Similarly, the returned list will implement
1276 * {@link RandomAccess} if the specified list does.
1277 *
1278 * @param <T> the class of the objects in the list
1279 * @param list the list for which an unmodifiable view is to be returned.
1280 * @return an unmodifiable view of the specified list.
1281 */
1282 public static <T> List<T> unmodifiableList(List<? extends T> list) {
1283 return (list instanceof RandomAccess ?
1284 new UnmodifiableRandomAccessList<>(list) :
1285 new UnmodifiableList<>(list));
1286 }
1287
1288 /**
1289 * @serial include
1290 */
1291 static class UnmodifiableList<E> extends UnmodifiableCollection<E>
1292 implements List<E> {
1293 private static final long serialVersionUID = -283967356065247728L;
1294
1295 final List<? extends E> list;
1296
1297 UnmodifiableList(List<? extends E> list) {
1298 super(list);
1299 this.list = list;
1300 }
1301
1302 public boolean equals(Object o) {return o == this || list.equals(o);}
1303 public int hashCode() {return list.hashCode();}
1304
1305 public E get(int index) {return list.get(index);}
1306 public E set(int index, E element) {
1307 throw new UnsupportedOperationException();
1308 }
1309 public void add(int index, E element) {
1310 throw new UnsupportedOperationException();
1311 }
1312 public E remove(int index) {
1313 throw new UnsupportedOperationException();
1314 }
1315 public int indexOf(Object o) {return list.indexOf(o);}
1316 public int lastIndexOf(Object o) {return list.lastIndexOf(o);}
1317 public boolean addAll(int index, Collection<? extends E> c) {
1318 throw new UnsupportedOperationException();
1319 }
1320
1321 @Override
1322 public void replaceAll(UnaryOperator<E> operator) {
1323 throw new UnsupportedOperationException();
1324 }
1325 @Override
1326 public void sort(Comparator<? super E> c) {
1327 throw new UnsupportedOperationException();
1328 }
1329
1330 public ListIterator<E> listIterator() {return listIterator(0);}
1331
1332 public ListIterator<E> listIterator(final int index) {
1333 return new ListIterator<E>() {
1334 private final ListIterator<? extends E> i
1335 = list.listIterator(index);
1336
1337 public boolean hasNext() {return i.hasNext();}
1338 public E next() {return i.next();}
1339 public boolean hasPrevious() {return i.hasPrevious();}
1340 public E previous() {return i.previous();}
1341 public int nextIndex() {return i.nextIndex();}
1342 public int previousIndex() {return i.previousIndex();}
1343
1344 public void remove() {
1345 throw new UnsupportedOperationException();
1346 }
1347 public void set(E e) {
1348 throw new UnsupportedOperationException();
1349 }
1350 public void add(E e) {
1351 throw new UnsupportedOperationException();
1352 }
1353
1354 @Override
1355 public void forEachRemaining(Consumer<? super E> action) {
1356 i.forEachRemaining(action);
1357 }
1358 };
1359 }
1360
1361 public List<E> subList(int fromIndex, int toIndex) {
1362 return new UnmodifiableList<>(list.subList(fromIndex, toIndex));
1363 }
1364
1365 /**
1366 * UnmodifiableRandomAccessList instances are serialized as
1367 * UnmodifiableList instances to allow them to be deserialized
1368 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList).
1369 * This method inverts the transformation. As a beneficial
1370 * side-effect, it also grafts the RandomAccess marker onto
1371 * UnmodifiableList instances that were serialized in pre-1.4 JREs.
1372 *
1373 * Note: Unfortunately, UnmodifiableRandomAccessList instances
1374 * serialized in 1.4.1 and deserialized in 1.4 will become
1375 * UnmodifiableList instances, as this method was missing in 1.4.
1376 */
1377 private Object readResolve() {
1378 return (list instanceof RandomAccess
1379 ? new UnmodifiableRandomAccessList<>(list)
1380 : this);
1381 }
1382 }
1383
1384 /**
1385 * @serial include
1386 */
1387 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E>
1388 implements RandomAccess
1389 {
1390 UnmodifiableRandomAccessList(List<? extends E> list) {
1391 super(list);
1392 }
1393
1394 public List<E> subList(int fromIndex, int toIndex) {
1395 return new UnmodifiableRandomAccessList<>(
1396 list.subList(fromIndex, toIndex));
1397 }
1398
1399 private static final long serialVersionUID = -2542308836966382001L;
1400
1401 /**
1402 * Allows instances to be deserialized in pre-1.4 JREs (which do
1403 * not have UnmodifiableRandomAccessList). UnmodifiableList has
1404 * a readResolve method that inverts this transformation upon
1405 * deserialization.
1406 */
1407 private Object writeReplace() {
1408 return new UnmodifiableList<>(list);
1409 }
1410 }
1411
1412 /**
1413 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1414 * specified map. Query operations on the returned map "read through"
1415 * to the specified map, and attempts to modify the returned
1416 * map, whether direct or via its collection views, result in an
1417 * {@code UnsupportedOperationException}.<p>
1418 *
1419 * The returned map will be serializable if the specified map
1420 * is serializable.
1421 *
1422 * @param <K> the class of the map keys
1423 * @param <V> the class of the map values
1424 * @param m the map for which an unmodifiable view is to be returned.
1425 * @return an unmodifiable view of the specified map.
1426 */
1427 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) {
1428 return new UnmodifiableMap<>(m);
1429 }
1430
1431 /**
1432 * @serial include
1433 */
1434 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable {
1435 private static final long serialVersionUID = -1034234728574286014L;
1436
1437 private final Map<? extends K, ? extends V> m;
1438
1439 UnmodifiableMap(Map<? extends K, ? extends V> m) {
1440 if (m==null)
1441 throw new NullPointerException();
1442 this.m = m;
1443 }
1444
1445 public int size() {return m.size();}
1446 public boolean isEmpty() {return m.isEmpty();}
1447 public boolean containsKey(Object key) {return m.containsKey(key);}
1448 public boolean containsValue(Object val) {return m.containsValue(val);}
1449 public V get(Object key) {return m.get(key);}
1450
1451 public V put(K key, V value) {
1452 throw new UnsupportedOperationException();
1453 }
1454 public V remove(Object key) {
1455 throw new UnsupportedOperationException();
1456 }
1457 public void putAll(Map<? extends K, ? extends V> m) {
1458 throw new UnsupportedOperationException();
1459 }
1460 public void clear() {
1461 throw new UnsupportedOperationException();
1462 }
1463
1464 private transient Set<K> keySet;
1465 private transient Set<Map.Entry<K,V>> entrySet;
1466 private transient Collection<V> values;
1467
1468 public Set<K> keySet() {
1469 if (keySet==null)
1470 keySet = unmodifiableSet(m.keySet());
1471 return keySet;
1472 }
1473
1474 public Set<Map.Entry<K,V>> entrySet() {
1475 if (entrySet==null)
1476 entrySet = new UnmodifiableEntrySet<>(m.entrySet());
1477 return entrySet;
1478 }
1479
1480 public Collection<V> values() {
1481 if (values==null)
1482 values = unmodifiableCollection(m.values());
1483 return values;
1484 }
1485
1486 public boolean equals(Object o) {return o == this || m.equals(o);}
1487 public int hashCode() {return m.hashCode();}
1488 public String toString() {return m.toString();}
1489
1490 // Override default methods in Map
1491 @Override
1492 @SuppressWarnings("unchecked")
1493 public V getOrDefault(Object k, V defaultValue) {
1494 // Safe cast as we don't change the value
1495 return ((Map<K, V>)m).getOrDefault(k, defaultValue);
1496 }
1497
1498 @Override
1499 public void forEach(BiConsumer<? super K, ? super V> action) {
1500 m.forEach(action);
1501 }
1502
1503 @Override
1504 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1505 throw new UnsupportedOperationException();
1506 }
1507
1508 @Override
1509 public V putIfAbsent(K key, V value) {
1510 throw new UnsupportedOperationException();
1511 }
1512
1513 @Override
1514 public boolean remove(Object key, Object value) {
1515 throw new UnsupportedOperationException();
1516 }
1517
1518 @Override
1519 public boolean replace(K key, V oldValue, V newValue) {
1520 throw new UnsupportedOperationException();
1521 }
1522
1523 @Override
1524 public V replace(K key, V value) {
1525 throw new UnsupportedOperationException();
1526 }
1527
1528 @Override
1529 public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
1530 throw new UnsupportedOperationException();
1531 }
1532
1533 @Override
1534 public V computeIfPresent(K key,
1535 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1536 throw new UnsupportedOperationException();
1537 }
1538
1539 @Override
1540 public V compute(K key,
1541 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1542 throw new UnsupportedOperationException();
1543 }
1544
1545 @Override
1546 public V merge(K key, V value,
1547 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1548 throw new UnsupportedOperationException();
1549 }
1550
1551 /**
1552 * We need this class in addition to UnmodifiableSet as
1553 * Map.Entries themselves permit modification of the backing Map
1554 * via their setValue operation. This class is subtle: there are
1555 * many possible attacks that must be thwarted.
1556 *
1557 * @serial include
1558 */
1559 static class UnmodifiableEntrySet<K,V>
1560 extends UnmodifiableSet<Map.Entry<K,V>> {
1561 private static final long serialVersionUID = 7854390611657943733L;
1562
1563 @SuppressWarnings({"unchecked", "rawtypes"})
1564 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
1565 // Need to cast to raw in order to work around a limitation in the type system
1566 super((Set)s);
1567 }
1568
1569 static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) {
1570 return e -> action.accept(new UnmodifiableEntry<>(e));
1571 }
1572
1573 public void forEach(Consumer<? super Entry<K, V>> action) {
1574 Objects.requireNonNull(action);
1575 c.forEach(entryConsumer(action));
1576 }
1577
1578 static final class UnmodifiableEntrySetSpliterator<K, V>
1579 implements Spliterator<Entry<K,V>> {
1580 final Spliterator<Map.Entry<K, V>> s;
1581
1582 UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>> s) {
1583 this.s = s;
1584 }
1585
1586 @Override
1587 public boolean tryAdvance(Consumer<? super Entry<K, V>> action) {
1588 Objects.requireNonNull(action);
1589 return s.tryAdvance(entryConsumer(action));
1590 }
1591
1592 @Override
1593 public void forEachRemaining(Consumer<? super Entry<K, V>> action) {
1594 Objects.requireNonNull(action);
1595 s.forEachRemaining(entryConsumer(action));
1596 }
1597
1598 @Override
1599 public Spliterator<Entry<K, V>> trySplit() {
1600 Spliterator<Entry<K, V>> split = s.trySplit();
1601 return split == null
1602 ? null
1603 : new UnmodifiableEntrySetSpliterator<>(split);
1604 }
1605
1606 @Override
1607 public long estimateSize() {
1608 return s.estimateSize();
1609 }
1610
1611 @Override
1612 public long getExactSizeIfKnown() {
1613 return s.getExactSizeIfKnown();
1614 }
1615
1616 @Override
1617 public int characteristics() {
1618 return s.characteristics();
1619 }
1620
1621 @Override
1622 public boolean hasCharacteristics(int characteristics) {
1623 return s.hasCharacteristics(characteristics);
1624 }
1625
1626 @Override
1627 public Comparator<? super Entry<K, V>> getComparator() {
1628 return s.getComparator();
1629 }
1630 }
1631
1632 @SuppressWarnings("unchecked")
1633 public Spliterator<Entry<K,V>> spliterator() {
1634 return new UnmodifiableEntrySetSpliterator<>(
1635 (Spliterator<Map.Entry<K, V>>) c.spliterator());
1636 }
1637
1638 @Override
1639 public Stream<Entry<K,V>> stream() {
1640 return StreamSupport.stream(spliterator(), false);
1641 }
1642
1643 @Override
1644 public Stream<Entry<K,V>> parallelStream() {
1645 return StreamSupport.stream(spliterator(), true);
1646 }
1647
1648 public Iterator<Map.Entry<K,V>> iterator() {
1649 return new Iterator<Map.Entry<K,V>>() {
1650 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator();
1651
1652 public boolean hasNext() {
1653 return i.hasNext();
1654 }
1655 public Map.Entry<K,V> next() {
1656 return new UnmodifiableEntry<>(i.next());
1657 }
1658 public void remove() {
1659 throw new UnsupportedOperationException();
1660 }
1661 };
1662 }
1663
1664 @SuppressWarnings("unchecked")
1665 public Object[] toArray() {
1666 Object[] a = c.toArray();
1667 for (int i=0; i<a.length; i++)
1668 a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]);
1669 return a;
1670 }
1671
1672 @SuppressWarnings("unchecked")
1673 public <T> T[] toArray(T[] a) {
1674 // We don't pass a to c.toArray, to avoid window of
1675 // vulnerability wherein an unscrupulous multithreaded client
1676 // could get his hands on raw (unwrapped) Entries from c.
1677 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
1678
1679 for (int i=0; i<arr.length; i++)
1680 arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]);
1681
1682 if (arr.length > a.length)
1683 return (T[])arr;
1684
1685 System.arraycopy(arr, 0, a, 0, arr.length);
1686 if (a.length > arr.length)
1687 a[arr.length] = null;
1688 return a;
1689 }
1690
1691 /**
1692 * This method is overridden to protect the backing set against
1693 * an object with a nefarious equals function that senses
1694 * that the equality-candidate is Map.Entry and calls its
1695 * setValue method.
1696 */
1697 public boolean contains(Object o) {
1698 if (!(o instanceof Map.Entry))
1699 return false;
1700 return c.contains(
1701 new UnmodifiableEntry<>((Map.Entry<?,?>) o));
1702 }
1703
1704 /**
1705 * The next two methods are overridden to protect against
1706 * an unscrupulous List whose contains(Object o) method senses
1707 * when o is a Map.Entry, and calls o.setValue.
1708 */
1709 public boolean containsAll(Collection<?> coll) {
1710 for (Object e : coll) {
1711 if (!contains(e)) // Invokes safe contains() above
1712 return false;
1713 }
1714 return true;
1715 }
1716 public boolean equals(Object o) {
1717 if (o == this)
1718 return true;
1719
1720 if (!(o instanceof Set))
1721 return false;
1722 Set<?> s = (Set<?>) o;
1723 if (s.size() != c.size())
1724 return false;
1725 return containsAll(s); // Invokes safe containsAll() above
1726 }
1727
1728 /**
1729 * This "wrapper class" serves two purposes: it prevents
1730 * the client from modifying the backing Map, by short-circuiting
1731 * the setValue method, and it protects the backing Map against
1732 * an ill-behaved Map.Entry that attempts to modify another
1733 * Map Entry when asked to perform an equality check.
1734 */
1735 private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> {
1736 private Map.Entry<? extends K, ? extends V> e;
1737
1738 UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e)
1739 {this.e = Objects.requireNonNull(e);}
1740
1741 public K getKey() {return e.getKey();}
1742 public V getValue() {return e.getValue();}
1743 public V setValue(V value) {
1744 throw new UnsupportedOperationException();
1745 }
1746 public int hashCode() {return e.hashCode();}
1747 public boolean equals(Object o) {
1748 if (this == o)
1749 return true;
1750 if (!(o instanceof Map.Entry))
1751 return false;
1752 Map.Entry<?,?> t = (Map.Entry<?,?>)o;
1753 return eq(e.getKey(), t.getKey()) &&
1754 eq(e.getValue(), t.getValue());
1755 }
1756 public String toString() {return e.toString();}
1757 }
1758 }
1759 }
1760
1761 /**
1762 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1763 * specified sorted map. Query operations on the returned sorted map "read through"
1764 * to the specified sorted map. Attempts to modify the returned
1765 * sorted map, whether direct, via its collection views, or via its
1766 * {@code subMap}, {@code headMap}, or {@code tailMap} views, result in
1767 * an {@code UnsupportedOperationException}.<p>
1768 *
1769 * The returned sorted map will be serializable if the specified sorted map
1770 * is serializable.
1771 *
1772 * @param <K> the class of the map keys
1773 * @param <V> the class of the map values
1774 * @param m the sorted map for which an unmodifiable view is to be
1775 * returned.
1776 * @return an unmodifiable view of the specified sorted map.
1777 */
1778 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) {
1779 return new UnmodifiableSortedMap<>(m);
1780 }
1781
1782 /**
1783 * @serial include
1784 */
1785 static class UnmodifiableSortedMap<K,V>
1786 extends UnmodifiableMap<K,V>
1787 implements SortedMap<K,V>, Serializable {
1788 private static final long serialVersionUID = -8806743815996713206L;
1789
1790 private final SortedMap<K, ? extends V> sm;
1791
1792 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; }
1793 public Comparator<? super K> comparator() { return sm.comparator(); }
1794 public SortedMap<K,V> subMap(K fromKey, K toKey)
1795 { return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); }
1796 public SortedMap<K,V> headMap(K toKey)
1797 { return new UnmodifiableSortedMap<>(sm.headMap(toKey)); }
1798 public SortedMap<K,V> tailMap(K fromKey)
1799 { return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); }
1800 public K firstKey() { return sm.firstKey(); }
1801 public K lastKey() { return sm.lastKey(); }
1802 }
1803
1804 /**
1805 * Returns an <a href="Collection.html#unmodview">unmodifiable view</a> of the
1806 * specified navigable map. Query operations on the returned navigable map "read
1807 * through" to the specified navigable map. Attempts to modify the returned
1808 * navigable map, whether direct, via its collection views, or via its
1809 * {@code subMap}, {@code headMap}, or {@code tailMap} views, result in
1810 * an {@code UnsupportedOperationException}.<p>
1811 *
1812 * The returned navigable map will be serializable if the specified
1813 * navigable map is serializable.
1814 *
1815 * @param <K> the class of the map keys
1816 * @param <V> the class of the map values
1817 * @param m the navigable map for which an unmodifiable view is to be
1818 * returned
1819 * @return an unmodifiable view of the specified navigable map
1820 * @since 1.8
1821 */
1822 public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) {
1823 return new UnmodifiableNavigableMap<>(m);
1824 }
1825
1826 /**
1827 * @serial include
1828 */
1829 static class UnmodifiableNavigableMap<K,V>
1830 extends UnmodifiableSortedMap<K,V>
1831 implements NavigableMap<K,V>, Serializable {
1832 private static final long serialVersionUID = -4858195264774772197L;
1833
1834 /**
1835 * A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve
1836 * to preserve singleton property.
1837 *
1838 * @param <K> type of keys, if there were any, and of bounds
1839 * @param <V> type of values, if there were any
1840 */
1841 private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V>
1842 implements Serializable {
1843
1844 private static final long serialVersionUID = -2239321462712562324L;
1845
1846 EmptyNavigableMap() { super(new TreeMap<>()); }
1847
1848 @Override
1849 public NavigableSet<K> navigableKeySet()
1850 { return emptyNavigableSet(); }
1851
1852 private Object readResolve() { return EMPTY_NAVIGABLE_MAP; }
1853 }
1854
1855 /**
1856 * Singleton for {@link emptyNavigableMap()} which is also immutable.
1857 */
1858 private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP =
1859 new EmptyNavigableMap<>();
1860
1861 /**
1862 * The instance we wrap and protect.
1863 */
1864 private final NavigableMap<K, ? extends V> nm;
1865
1866 UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m)
1867 {super(m); nm = m;}
1868
1869 public K lowerKey(K key) { return nm.lowerKey(key); }
1870 public K floorKey(K key) { return nm.floorKey(key); }
1871 public K ceilingKey(K key) { return nm.ceilingKey(key); }
1872 public K higherKey(K key) { return nm.higherKey(key); }
1873
1874 @SuppressWarnings("unchecked")
1875 public Entry<K, V> lowerEntry(K key) {
1876 Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key);
1877 return (null != lower)
1878 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(lower)
1879 : null;
1880 }
1881
1882 @SuppressWarnings("unchecked")
1883 public Entry<K, V> floorEntry(K key) {
1884 Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key);
1885 return (null != floor)
1886 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(floor)
1887 : null;
1888 }
1889
1890 @SuppressWarnings("unchecked")
1891 public Entry<K, V> ceilingEntry(K key) {
1892 Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key);
1893 return (null != ceiling)
1894 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(ceiling)
1895 : null;
1896 }
1897
1898
1899 @SuppressWarnings("unchecked")
1900 public Entry<K, V> higherEntry(K key) {
1901 Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key);
1902 return (null != higher)
1903 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(higher)
1904 : null;
1905 }
1906
1907 @SuppressWarnings("unchecked")
1908 public Entry<K, V> firstEntry() {
1909 Entry<K,V> first = (Entry<K, V>) nm.firstEntry();
1910 return (null != first)
1911 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(first)
1912 : null;
1913 }
1914
1915 @SuppressWarnings("unchecked")
1916 public Entry<K, V> lastEntry() {
1917 Entry<K,V> last = (Entry<K, V>) nm.lastEntry();
1918 return (null != last)
1919 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(last)
1920 : null;
1921 }
1922
1923 public Entry<K, V> pollFirstEntry()
1924 { throw new UnsupportedOperationException(); }
1925 public Entry<K, V> pollLastEntry()
1926 { throw new UnsupportedOperationException(); }
1927 public NavigableMap<K, V> descendingMap()
1928 { return unmodifiableNavigableMap(nm.descendingMap()); }
1929 public NavigableSet<K> navigableKeySet()
1930 { return unmodifiableNavigableSet(nm.navigableKeySet()); }
1931 public NavigableSet<K> descendingKeySet()
1932 { return unmodifiableNavigableSet(nm.descendingKeySet()); }
1933
1934 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
1935 return unmodifiableNavigableMap(
1936 nm.subMap(fromKey, fromInclusive, toKey, toInclusive));
1937 }
1938
1939 public NavigableMap<K, V> headMap(K toKey, boolean inclusive)
1940 { return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); }
1941 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive)
1942 { return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); }
1943 }
1944
1945 // Synch Wrappers
1946
1947 /**
1948 * Returns a synchronized (thread-safe) collection backed by the specified
1949 * collection. In order to guarantee serial access, it is critical that
1950 * <strong>all</strong> access to the backing collection is accomplished
1951 * through the returned collection.<p>
1952 *
1953 * It is imperative that the user manually synchronize on the returned
1954 * collection when traversing it via {@link Iterator}, {@link Spliterator}
1955 * or {@link Stream}:
1956 * <pre>
1957 * Collection c = Collections.synchronizedCollection(myCollection);
1958 * ...
1959 * synchronized (c) {
1960 * Iterator i = c.iterator(); // Must be in the synchronized block
1961 * while (i.hasNext())
1962 * foo(i.next());
1963 * }
1964 * </pre>
1965 * Failure to follow this advice may result in non-deterministic behavior.
1966 *
1967 * <p>The returned collection does <i>not</i> pass the {@code hashCode}
1968 * and {@code equals} operations through to the backing collection, but
1969 * relies on {@code Object}'s equals and hashCode methods. This is
1970 * necessary to preserve the contracts of these operations in the case
1971 * that the backing collection is a set or a list.<p>
1972 *
1973 * The returned collection will be serializable if the specified collection
1974 * is serializable.
1975 *
1976 * @param <T> the class of the objects in the collection
1977 * @param c the collection to be "wrapped" in a synchronized collection.
1978 * @return a synchronized view of the specified collection.
1979 */
1980 public static <T> Collection<T> synchronizedCollection(Collection<T> c) {
1981 return new SynchronizedCollection<>(c);
1982 }
1983
1984 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) {
1985 return new SynchronizedCollection<>(c, mutex);
1986 }
1987
1988 /**
1989 * @serial include
1990 */
1991 static class SynchronizedCollection<E> implements Collection<E>, Serializable {
1992 private static final long serialVersionUID = 3053995032091335093L;
1993
1994 final Collection<E> c; // Backing Collection
1995 final Object mutex; // Object on which to synchronize
1996
1997 SynchronizedCollection(Collection<E> c) {
1998 this.c = Objects.requireNonNull(c);
1999 mutex = this;
2000 }
2001
2002 SynchronizedCollection(Collection<E> c, Object mutex) {
2003 this.c = Objects.requireNonNull(c);
2004 this.mutex = Objects.requireNonNull(mutex);
2005 }
2006
2007 public int size() {
2008 synchronized (mutex) {return c.size();}
2009 }
2010 public boolean isEmpty() {
2011 synchronized (mutex) {return c.isEmpty();}
2012 }
2013 public boolean contains(Object o) {
2014 synchronized (mutex) {return c.contains(o);}
2015 }
2016 public Object[] toArray() {
2017 synchronized (mutex) {return c.toArray();}
2018 }
2019 public <T> T[] toArray(T[] a) {
2020 synchronized (mutex) {return c.toArray(a);}
2021 }
2022
2023 public Iterator<E> iterator() {
2024 return c.iterator(); // Must be manually synched by user!
2025 }
2026
2027 public boolean add(E e) {
2028 synchronized (mutex) {return c.add(e);}
2029 }
2030 public boolean remove(Object o) {
2031 synchronized (mutex) {return c.remove(o);}
2032 }
2033
2034 public boolean containsAll(Collection<?> coll) {
2035 synchronized (mutex) {return c.containsAll(coll);}
2036 }
2037 public boolean addAll(Collection<? extends E> coll) {
2038 synchronized (mutex) {return c.addAll(coll);}
2039 }
2040 public boolean removeAll(Collection<?> coll) {
2041 synchronized (mutex) {return c.removeAll(coll);}
2042 }
2043 public boolean retainAll(Collection<?> coll) {
2044 synchronized (mutex) {return c.retainAll(coll);}
2045 }
2046 public void clear() {
2047 synchronized (mutex) {c.clear();}
2048 }
2049 public String toString() {
2050 synchronized (mutex) {return c.toString();}
2051 }
2052 // Override default methods in Collection
2053 @Override
2054 public void forEach(Consumer<? super E> consumer) {
2055 synchronized (mutex) {c.forEach(consumer);}
2056 }
2057 @Override
2058 public boolean removeIf(Predicate<? super E> filter) {
2059 synchronized (mutex) {return c.removeIf(filter);}
2060 }
2061 @Override
2062 public Spliterator<E> spliterator() {
2063 return c.spliterator(); // Must be manually synched by user!
2064 }
2065 @Override
2066 public Stream<E> stream() {
2067 return c.stream(); // Must be manually synched by user!
2068 }
2069 @Override
2070 public Stream<E> parallelStream() {
2071 return c.parallelStream(); // Must be manually synched by user!
2072 }
2073 private void writeObject(ObjectOutputStream s) throws IOException {
2074 synchronized (mutex) {s.defaultWriteObject();}
2075 }
2076 }
2077
2078 /**
2079 * Returns a synchronized (thread-safe) set backed by the specified
2080 * set. In order to guarantee serial access, it is critical that
2081 * <strong>all</strong> access to the backing set is accomplished
2082 * through the returned set.<p>
2083 *
2084 * It is imperative that the user manually synchronize on the returned
2085 * collection when traversing it via {@link Iterator}, {@link Spliterator}
2086 * or {@link Stream}:
2087 * <pre>
2088 * Set s = Collections.synchronizedSet(new HashSet());
2089 * ...
2090 * synchronized (s) {
2091 * Iterator i = s.iterator(); // Must be in the synchronized block
2092 * while (i.hasNext())
2093 * foo(i.next());
2094 * }
2095 * </pre>
2096 * Failure to follow this advice may result in non-deterministic behavior.
2097 *
2098 * <p>The returned set will be serializable if the specified set is
2099 * serializable.
2100 *
2101 * @param <T> the class of the objects in the set
2102 * @param s the set to be "wrapped" in a synchronized set.
2103 * @return a synchronized view of the specified set.
2104 */
2105 public static <T> Set<T> synchronizedSet(Set<T> s) {
2106 return new SynchronizedSet<>(s);
2107 }
2108
2109 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) {
2110 return new SynchronizedSet<>(s, mutex);
2111 }
2112
2113 /**
2114 * @serial include
2115 */
2116 static class SynchronizedSet<E>
2117 extends SynchronizedCollection<E>
2118 implements Set<E> {
2119 private static final long serialVersionUID = 487447009682186044L;
2120
2121 SynchronizedSet(Set<E> s) {
2122 super(s);
2123 }
2124 SynchronizedSet(Set<E> s, Object mutex) {
2125 super(s, mutex);
2126 }
2127
2128 public boolean equals(Object o) {
2129 if (this == o)
2130 return true;
2131 synchronized (mutex) {return c.equals(o);}
2132 }
2133 public int hashCode() {
2134 synchronized (mutex) {return c.hashCode();}
2135 }
2136 }
2137
2138 /**
2139 * Returns a synchronized (thread-safe) sorted set backed by the specified
2140 * sorted set. In order to guarantee serial access, it is critical that
2141 * <strong>all</strong> access to the backing sorted set is accomplished
2142 * through the returned sorted set (or its views).<p>
2143 *
2144 * It is imperative that the user manually synchronize on the returned
2145 * sorted set when traversing it or any of its {@code subSet},
2146 * {@code headSet}, or {@code tailSet} views via {@link Iterator},
2147 * {@link Spliterator} or {@link Stream}:
2148 * <pre>
2149 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2150 * ...
2151 * synchronized (s) {
2152 * Iterator i = s.iterator(); // Must be in the synchronized block
2153 * while (i.hasNext())
2154 * foo(i.next());
2155 * }
2156 * </pre>
2157 * or:
2158 * <pre>
2159 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet());
2160 * SortedSet s2 = s.headSet(foo);
2161 * ...
2162 * synchronized (s) { // Note: s, not s2!!!
2163 * Iterator i = s2.iterator(); // Must be in the synchronized block
2164 * while (i.hasNext())
2165 * foo(i.next());
2166 * }
2167 * </pre>
2168 * Failure to follow this advice may result in non-deterministic behavior.
2169 *
2170 * <p>The returned sorted set will be serializable if the specified
2171 * sorted set is serializable.
2172 *
2173 * @param <T> the class of the objects in the set
2174 * @param s the sorted set to be "wrapped" in a synchronized sorted set.
2175 * @return a synchronized view of the specified sorted set.
2176 */
2177 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) {
2178 return new SynchronizedSortedSet<>(s);
2179 }
2180
2181 /**
2182 * @serial include
2183 */
2184 static class SynchronizedSortedSet<E>
2185 extends SynchronizedSet<E>
2186 implements SortedSet<E>
2187 {
2188 private static final long serialVersionUID = 8695801310862127406L;
2189
2190 private final SortedSet<E> ss;
2191
2192 SynchronizedSortedSet(SortedSet<E> s) {
2193 super(s);
2194 ss = s;
2195 }
2196 SynchronizedSortedSet(SortedSet<E> s, Object mutex) {
2197 super(s, mutex);
2198 ss = s;
2199 }
2200
2201 public Comparator<? super E> comparator() {
2202 synchronized (mutex) {return ss.comparator();}
2203 }
2204
2205 public SortedSet<E> subSet(E fromElement, E toElement) {
2206 synchronized (mutex) {
2207 return new SynchronizedSortedSet<>(
2208 ss.subSet(fromElement, toElement), mutex);
2209 }
2210 }
2211 public SortedSet<E> headSet(E toElement) {
2212 synchronized (mutex) {
2213 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex);
2214 }
2215 }
2216 public SortedSet<E> tailSet(E fromElement) {
2217 synchronized (mutex) {
2218 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex);
2219 }
2220 }
2221
2222 public E first() {
2223 synchronized (mutex) {return ss.first();}
2224 }
2225 public E last() {
2226 synchronized (mutex) {return ss.last();}
2227 }
2228 }
2229
2230 /**
2231 * Returns a synchronized (thread-safe) navigable set backed by the
2232 * specified navigable set. In order to guarantee serial access, it is
2233 * critical that <strong>all</strong> access to the backing navigable set is
2234 * accomplished through the returned navigable set (or its views).<p>
2235 *
2236 * It is imperative that the user manually synchronize on the returned
2237 * navigable set when traversing it, or any of its {@code subSet},
2238 * {@code headSet}, or {@code tailSet} views, via {@link Iterator},
2239 * {@link Spliterator} or {@link Stream}:
2240 * <pre>
2241 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
2242 * ...
2243 * synchronized (s) {
2244 * Iterator i = s.iterator(); // Must be in the synchronized block
2245 * while (i.hasNext())
2246 * foo(i.next());
2247 * }
2248 * </pre>
2249 * or:
2250 * <pre>
2251 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet());
2252 * NavigableSet s2 = s.headSet(foo, true);
2253 * ...
2254 * synchronized (s) { // Note: s, not s2!!!
2255 * Iterator i = s2.iterator(); // Must be in the synchronized block
2256 * while (i.hasNext())
2257 * foo(i.next());
2258 * }
2259 * </pre>
2260 * Failure to follow this advice may result in non-deterministic behavior.
2261 *
2262 * <p>The returned navigable set will be serializable if the specified
2263 * navigable set is serializable.
2264 *
2265 * @param <T> the class of the objects in the set
2266 * @param s the navigable set to be "wrapped" in a synchronized navigable
2267 * set
2268 * @return a synchronized view of the specified navigable set
2269 * @since 1.8
2270 */
2271 public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) {
2272 return new SynchronizedNavigableSet<>(s);
2273 }
2274
2275 /**
2276 * @serial include
2277 */
2278 static class SynchronizedNavigableSet<E>
2279 extends SynchronizedSortedSet<E>
2280 implements NavigableSet<E>
2281 {
2282 private static final long serialVersionUID = -5505529816273629798L;
2283
2284 private final NavigableSet<E> ns;
2285
2286 SynchronizedNavigableSet(NavigableSet<E> s) {
2287 super(s);
2288 ns = s;
2289 }
2290
2291 SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) {
2292 super(s, mutex);
2293 ns = s;
2294 }
2295 public E lower(E e) { synchronized (mutex) {return ns.lower(e);} }
2296 public E floor(E e) { synchronized (mutex) {return ns.floor(e);} }
2297 public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} }
2298 public E higher(E e) { synchronized (mutex) {return ns.higher(e);} }
2299 public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} }
2300 public E pollLast() { synchronized (mutex) {return ns.pollLast();} }
2301
2302 public NavigableSet<E> descendingSet() {
2303 synchronized (mutex) {
2304 return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex);
2305 }
2306 }
2307
2308 public Iterator<E> descendingIterator()
2309 { synchronized (mutex) { return descendingSet().iterator(); } }
2310
2311 public NavigableSet<E> subSet(E fromElement, E toElement) {
2312 synchronized (mutex) {
2313 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex);
2314 }
2315 }
2316 public NavigableSet<E> headSet(E toElement) {
2317 synchronized (mutex) {
2318 return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex);
2319 }
2320 }
2321 public NavigableSet<E> tailSet(E fromElement) {
2322 synchronized (mutex) {
2323 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, true), mutex);
2324 }
2325 }
2326
2327 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
2328 synchronized (mutex) {
2329 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex);
2330 }
2331 }
2332
2333 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
2334 synchronized (mutex) {
2335 return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex);
2336 }
2337 }
2338
2339 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
2340 synchronized (mutex) {
2341 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive), mutex);
2342 }
2343 }
2344 }
2345
2346 /**
2347 * Returns a synchronized (thread-safe) list backed by the specified
2348 * list. In order to guarantee serial access, it is critical that
2349 * <strong>all</strong> access to the backing list is accomplished
2350 * through the returned list.<p>
2351 *
2352 * It is imperative that the user manually synchronize on the returned
2353 * list when traversing it via {@link Iterator}, {@link Spliterator}
2354 * or {@link Stream}:
2355 * <pre>
2356 * List list = Collections.synchronizedList(new ArrayList());
2357 * ...
2358 * synchronized (list) {
2359 * Iterator i = list.iterator(); // Must be in synchronized block
2360 * while (i.hasNext())
2361 * foo(i.next());
2362 * }
2363 * </pre>
2364 * Failure to follow this advice may result in non-deterministic behavior.
2365 *
2366 * <p>The returned list will be serializable if the specified list is
2367 * serializable.
2368 *
2369 * @param <T> the class of the objects in the list
2370 * @param list the list to be "wrapped" in a synchronized list.
2371 * @return a synchronized view of the specified list.
2372 */
2373 public static <T> List<T> synchronizedList(List<T> list) {
2374 return (list instanceof RandomAccess ?
2375 new SynchronizedRandomAccessList<>(list) :
2376 new SynchronizedList<>(list));
2377 }
2378
2379 static <T> List<T> synchronizedList(List<T> list, Object mutex) {
2380 return (list instanceof RandomAccess ?
2381 new SynchronizedRandomAccessList<>(list, mutex) :
2382 new SynchronizedList<>(list, mutex));
2383 }
2384
2385 /**
2386 * @serial include
2387 */
2388 static class SynchronizedList<E>
2389 extends SynchronizedCollection<E>
2390 implements List<E> {
2391 private static final long serialVersionUID = -7754090372962971524L;
2392
2393 final List<E> list;
2394
2395 SynchronizedList(List<E> list) {
2396 super(list);
2397 this.list = list;
2398 }
2399 SynchronizedList(List<E> list, Object mutex) {
2400 super(list, mutex);
2401 this.list = list;
2402 }
2403
2404 public boolean equals(Object o) {
2405 if (this == o)
2406 return true;
2407 synchronized (mutex) {return list.equals(o);}
2408 }
2409 public int hashCode() {
2410 synchronized (mutex) {return list.hashCode();}
2411 }
2412
2413 public E get(int index) {
2414 synchronized (mutex) {return list.get(index);}
2415 }
2416 public E set(int index, E element) {
2417 synchronized (mutex) {return list.set(index, element);}
2418 }
2419 public void add(int index, E element) {
2420 synchronized (mutex) {list.add(index, element);}
2421 }
2422 public E remove(int index) {
2423 synchronized (mutex) {return list.remove(index);}
2424 }
2425
2426 public int indexOf(Object o) {
2427 synchronized (mutex) {return list.indexOf(o);}
2428 }
2429 public int lastIndexOf(Object o) {
2430 synchronized (mutex) {return list.lastIndexOf(o);}
2431 }
2432
2433 public boolean addAll(int index, Collection<? extends E> c) {
2434 synchronized (mutex) {return list.addAll(index, c);}
2435 }
2436
2437 public ListIterator<E> listIterator() {
2438 return list.listIterator(); // Must be manually synched by user
2439 }
2440
2441 public ListIterator<E> listIterator(int index) {
2442 return list.listIterator(index); // Must be manually synched by user
2443 }
2444
2445 public List<E> subList(int fromIndex, int toIndex) {
2446 synchronized (mutex) {
2447 return new SynchronizedList<>(list.subList(fromIndex, toIndex),
2448 mutex);
2449 }
2450 }
2451
2452 @Override
2453 public void replaceAll(UnaryOperator<E> operator) {
2454 synchronized (mutex) {list.replaceAll(operator);}
2455 }
2456 @Override
2457 public void sort(Comparator<? super E> c) {
2458 synchronized (mutex) {list.sort(c);}
2459 }
2460
2461 /**
2462 * SynchronizedRandomAccessList instances are serialized as
2463 * SynchronizedList instances to allow them to be deserialized
2464 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList).
2465 * This method inverts the transformation. As a beneficial
2466 * side-effect, it also grafts the RandomAccess marker onto
2467 * SynchronizedList instances that were serialized in pre-1.4 JREs.
2468 *
2469 * Note: Unfortunately, SynchronizedRandomAccessList instances
2470 * serialized in 1.4.1 and deserialized in 1.4 will become
2471 * SynchronizedList instances, as this method was missing in 1.4.
2472 */
2473 private Object readResolve() {
2474 return (list instanceof RandomAccess
2475 ? new SynchronizedRandomAccessList<>(list)
2476 : this);
2477 }
2478 }
2479
2480 /**
2481 * @serial include
2482 */
2483 static class SynchronizedRandomAccessList<E>
2484 extends SynchronizedList<E>
2485 implements RandomAccess {
2486
2487 SynchronizedRandomAccessList(List<E> list) {
2488 super(list);
2489 }
2490
2491 SynchronizedRandomAccessList(List<E> list, Object mutex) {
2492 super(list, mutex);
2493 }
2494
2495 public List<E> subList(int fromIndex, int toIndex) {
2496 synchronized (mutex) {
2497 return new SynchronizedRandomAccessList<>(
2498 list.subList(fromIndex, toIndex), mutex);
2499 }
2500 }
2501
2502 private static final long serialVersionUID = 1530674583602358482L;
2503
2504 /**
2505 * Allows instances to be deserialized in pre-1.4 JREs (which do
2506 * not have SynchronizedRandomAccessList). SynchronizedList has
2507 * a readResolve method that inverts this transformation upon
2508 * deserialization.
2509 */
2510 private Object writeReplace() {
2511 return new SynchronizedList<>(list);
2512 }
2513 }
2514
2515 /**
2516 * Returns a synchronized (thread-safe) map backed by the specified
2517 * map. In order to guarantee serial access, it is critical that
2518 * <strong>all</strong> access to the backing map is accomplished
2519 * through the returned map.<p>
2520 *
2521 * It is imperative that the user manually synchronize on the returned
2522 * map when traversing any of its collection views via {@link Iterator},
2523 * {@link Spliterator} or {@link Stream}:
2524 * <pre>
2525 * Map m = Collections.synchronizedMap(new HashMap());
2526 * ...
2527 * Set s = m.keySet(); // Needn't be in synchronized block
2528 * ...
2529 * synchronized (m) { // Synchronizing on m, not s!
2530 * Iterator i = s.iterator(); // Must be in synchronized block
2531 * while (i.hasNext())
2532 * foo(i.next());
2533 * }
2534 * </pre>
2535 * Failure to follow this advice may result in non-deterministic behavior.
2536 *
2537 * <p>The returned map will be serializable if the specified map is
2538 * serializable.
2539 *
2540 * @param <K> the class of the map keys
2541 * @param <V> the class of the map values
2542 * @param m the map to be "wrapped" in a synchronized map.
2543 * @return a synchronized view of the specified map.
2544 */
2545 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) {
2546 return new SynchronizedMap<>(m);
2547 }
2548
2549 /**
2550 * @serial include
2551 */
2552 private static class SynchronizedMap<K,V>
2553 implements Map<K,V>, Serializable {
2554 private static final long serialVersionUID = 1978198479659022715L;
2555
2556 private final Map<K,V> m; // Backing Map
2557 final Object mutex; // Object on which to synchronize
2558
2559 SynchronizedMap(Map<K,V> m) {
2560 this.m = Objects.requireNonNull(m);
2561 mutex = this;
2562 }
2563
2564 SynchronizedMap(Map<K,V> m, Object mutex) {
2565 this.m = m;
2566 this.mutex = mutex;
2567 }
2568
2569 public int size() {
2570 synchronized (mutex) {return m.size();}
2571 }
2572 public boolean isEmpty() {
2573 synchronized (mutex) {return m.isEmpty();}
2574 }
2575 public boolean containsKey(Object key) {
2576 synchronized (mutex) {return m.containsKey(key);}
2577 }
2578 public boolean containsValue(Object value) {
2579 synchronized (mutex) {return m.containsValue(value);}
2580 }
2581 public V get(Object key) {
2582 synchronized (mutex) {return m.get(key);}
2583 }
2584
2585 public V put(K key, V value) {
2586 synchronized (mutex) {return m.put(key, value);}
2587 }
2588 public V remove(Object key) {
2589 synchronized (mutex) {return m.remove(key);}
2590 }
2591 public void putAll(Map<? extends K, ? extends V> map) {
2592 synchronized (mutex) {m.putAll(map);}
2593 }
2594 public void clear() {
2595 synchronized (mutex) {m.clear();}
2596 }
2597
2598 private transient Set<K> keySet;
2599 private transient Set<Map.Entry<K,V>> entrySet;
2600 private transient Collection<V> values;
2601
2602 public Set<K> keySet() {
2603 synchronized (mutex) {
2604 if (keySet==null)
2605 keySet = new SynchronizedSet<>(m.keySet(), mutex);
2606 return keySet;
2607 }
2608 }
2609
2610 public Set<Map.Entry<K,V>> entrySet() {
2611 synchronized (mutex) {
2612 if (entrySet==null)
2613 entrySet = new SynchronizedSet<>(m.entrySet(), mutex);
2614 return entrySet;
2615 }
2616 }
2617
2618 public Collection<V> values() {
2619 synchronized (mutex) {
2620 if (values==null)
2621 values = new SynchronizedCollection<>(m.values(), mutex);
2622 return values;
2623 }
2624 }
2625
2626 public boolean equals(Object o) {
2627 if (this == o)
2628 return true;
2629 synchronized (mutex) {return m.equals(o);}
2630 }
2631 public int hashCode() {
2632 synchronized (mutex) {return m.hashCode();}
2633 }
2634 public String toString() {
2635 synchronized (mutex) {return m.toString();}
2636 }
2637
2638 // Override default methods in Map
2639 @Override
2640 public V getOrDefault(Object k, V defaultValue) {
2641 synchronized (mutex) {return m.getOrDefault(k, defaultValue);}
2642 }
2643 @Override
2644 public void forEach(BiConsumer<? super K, ? super V> action) {
2645 synchronized (mutex) {m.forEach(action);}
2646 }
2647 @Override
2648 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
2649 synchronized (mutex) {m.replaceAll(function);}
2650 }
2651 @Override
2652 public V putIfAbsent(K key, V value) {
2653 synchronized (mutex) {return m.putIfAbsent(key, value);}
2654 }
2655 @Override
2656 public boolean remove(Object key, Object value) {
2657 synchronized (mutex) {return m.remove(key, value);}
2658 }
2659 @Override
2660 public boolean replace(K key, V oldValue, V newValue) {
2661 synchronized (mutex) {return m.replace(key, oldValue, newValue);}
2662 }
2663 @Override
2664 public V replace(K key, V value) {
2665 synchronized (mutex) {return m.replace(key, value);}
2666 }
2667 @Override
2668 public V computeIfAbsent(K key,
2669 Function<? super K, ? extends V> mappingFunction) {
2670 synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);}
2671 }
2672 @Override
2673 public V computeIfPresent(K key,
2674 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2675 synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);}
2676 }
2677 @Override
2678 public V compute(K key,
2679 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
2680 synchronized (mutex) {return m.compute(key, remappingFunction);}
2681 }
2682 @Override
2683 public V merge(K key, V value,
2684 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
2685 synchronized (mutex) {return m.merge(key, value, remappingFunction);}
2686 }
2687
2688 private void writeObject(ObjectOutputStream s) throws IOException {
2689 synchronized (mutex) {s.defaultWriteObject();}
2690 }
2691 }
2692
2693 /**
2694 * Returns a synchronized (thread-safe) sorted map backed by the specified
2695 * sorted map. In order to guarantee serial access, it is critical that
2696 * <strong>all</strong> access to the backing sorted map is accomplished
2697 * through the returned sorted map (or its views).<p>
2698 *
2699 * It is imperative that the user manually synchronize on the returned
2700 * sorted map when traversing any of its collection views, or the
2701 * collections views of any of its {@code subMap}, {@code headMap} or
2702 * {@code tailMap} views, via {@link Iterator}, {@link Spliterator} or
2703 * {@link Stream}:
2704 * <pre>
2705 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2706 * ...
2707 * Set s = m.keySet(); // Needn't be in synchronized block
2708 * ...
2709 * synchronized (m) { // Synchronizing on m, not s!
2710 * Iterator i = s.iterator(); // Must be in synchronized block
2711 * while (i.hasNext())
2712 * foo(i.next());
2713 * }
2714 * </pre>
2715 * or:
2716 * <pre>
2717 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap());
2718 * SortedMap m2 = m.subMap(foo, bar);
2719 * ...
2720 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2721 * ...
2722 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2723 * Iterator i = s2.iterator(); // Must be in synchronized block
2724 * while (i.hasNext())
2725 * foo(i.next());
2726 * }
2727 * </pre>
2728 * Failure to follow this advice may result in non-deterministic behavior.
2729 *
2730 * <p>The returned sorted map will be serializable if the specified
2731 * sorted map is serializable.
2732 *
2733 * @param <K> the class of the map keys
2734 * @param <V> the class of the map values
2735 * @param m the sorted map to be "wrapped" in a synchronized sorted map.
2736 * @return a synchronized view of the specified sorted map.
2737 */
2738 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) {
2739 return new SynchronizedSortedMap<>(m);
2740 }
2741
2742 /**
2743 * @serial include
2744 */
2745 static class SynchronizedSortedMap<K,V>
2746 extends SynchronizedMap<K,V>
2747 implements SortedMap<K,V>
2748 {
2749 private static final long serialVersionUID = -8798146769416483793L;
2750
2751 private final SortedMap<K,V> sm;
2752
2753 SynchronizedSortedMap(SortedMap<K,V> m) {
2754 super(m);
2755 sm = m;
2756 }
2757 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) {
2758 super(m, mutex);
2759 sm = m;
2760 }
2761
2762 public Comparator<? super K> comparator() {
2763 synchronized (mutex) {return sm.comparator();}
2764 }
2765
2766 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2767 synchronized (mutex) {
2768 return new SynchronizedSortedMap<>(
2769 sm.subMap(fromKey, toKey), mutex);
2770 }
2771 }
2772 public SortedMap<K,V> headMap(K toKey) {
2773 synchronized (mutex) {
2774 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex);
2775 }
2776 }
2777 public SortedMap<K,V> tailMap(K fromKey) {
2778 synchronized (mutex) {
2779 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex);
2780 }
2781 }
2782
2783 public K firstKey() {
2784 synchronized (mutex) {return sm.firstKey();}
2785 }
2786 public K lastKey() {
2787 synchronized (mutex) {return sm.lastKey();}
2788 }
2789 }
2790
2791 /**
2792 * Returns a synchronized (thread-safe) navigable map backed by the
2793 * specified navigable map. In order to guarantee serial access, it is
2794 * critical that <strong>all</strong> access to the backing navigable map is
2795 * accomplished through the returned navigable map (or its views).<p>
2796 *
2797 * It is imperative that the user manually synchronize on the returned
2798 * navigable map when traversing any of its collection views, or the
2799 * collections views of any of its {@code subMap}, {@code headMap} or
2800 * {@code tailMap} views, via {@link Iterator}, {@link Spliterator} or
2801 * {@link Stream}:
2802 * <pre>
2803 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
2804 * ...
2805 * Set s = m.keySet(); // Needn't be in synchronized block
2806 * ...
2807 * synchronized (m) { // Synchronizing on m, not s!
2808 * Iterator i = s.iterator(); // Must be in synchronized block
2809 * while (i.hasNext())
2810 * foo(i.next());
2811 * }
2812 * </pre>
2813 * or:
2814 * <pre>
2815 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap());
2816 * NavigableMap m2 = m.subMap(foo, true, bar, false);
2817 * ...
2818 * Set s2 = m2.keySet(); // Needn't be in synchronized block
2819 * ...
2820 * synchronized (m) { // Synchronizing on m, not m2 or s2!
2821 * Iterator i = s.iterator(); // Must be in synchronized block
2822 * while (i.hasNext())
2823 * foo(i.next());
2824 * }
2825 * </pre>
2826 * Failure to follow this advice may result in non-deterministic behavior.
2827 *
2828 * <p>The returned navigable map will be serializable if the specified
2829 * navigable map is serializable.
2830 *
2831 * @param <K> the class of the map keys
2832 * @param <V> the class of the map values
2833 * @param m the navigable map to be "wrapped" in a synchronized navigable
2834 * map
2835 * @return a synchronized view of the specified navigable map.
2836 * @since 1.8
2837 */
2838 public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) {
2839 return new SynchronizedNavigableMap<>(m);
2840 }
2841
2842 /**
2843 * A synchronized NavigableMap.
2844 *
2845 * @serial include
2846 */
2847 static class SynchronizedNavigableMap<K,V>
2848 extends SynchronizedSortedMap<K,V>
2849 implements NavigableMap<K,V>
2850 {
2851 private static final long serialVersionUID = 699392247599746807L;
2852
2853 private final NavigableMap<K,V> nm;
2854
2855 SynchronizedNavigableMap(NavigableMap<K,V> m) {
2856 super(m);
2857 nm = m;
2858 }
2859 SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) {
2860 super(m, mutex);
2861 nm = m;
2862 }
2863
2864 public Entry<K, V> lowerEntry(K key)
2865 { synchronized (mutex) { return nm.lowerEntry(key); } }
2866 public K lowerKey(K key)
2867 { synchronized (mutex) { return nm.lowerKey(key); } }
2868 public Entry<K, V> floorEntry(K key)
2869 { synchronized (mutex) { return nm.floorEntry(key); } }
2870 public K floorKey(K key)
2871 { synchronized (mutex) { return nm.floorKey(key); } }
2872 public Entry<K, V> ceilingEntry(K key)
2873 { synchronized (mutex) { return nm.ceilingEntry(key); } }
2874 public K ceilingKey(K key)
2875 { synchronized (mutex) { return nm.ceilingKey(key); } }
2876 public Entry<K, V> higherEntry(K key)
2877 { synchronized (mutex) { return nm.higherEntry(key); } }
2878 public K higherKey(K key)
2879 { synchronized (mutex) { return nm.higherKey(key); } }
2880 public Entry<K, V> firstEntry()
2881 { synchronized (mutex) { return nm.firstEntry(); } }
2882 public Entry<K, V> lastEntry()
2883 { synchronized (mutex) { return nm.lastEntry(); } }
2884 public Entry<K, V> pollFirstEntry()
2885 { synchronized (mutex) { return nm.pollFirstEntry(); } }
2886 public Entry<K, V> pollLastEntry()
2887 { synchronized (mutex) { return nm.pollLastEntry(); } }
2888
2889 public NavigableMap<K, V> descendingMap() {
2890 synchronized (mutex) {
2891 return
2892 new SynchronizedNavigableMap<>(nm.descendingMap(), mutex);
2893 }
2894 }
2895
2896 public NavigableSet<K> keySet() {
2897 return navigableKeySet();
2898 }
2899
2900 public NavigableSet<K> navigableKeySet() {
2901 synchronized (mutex) {
2902 return new SynchronizedNavigableSet<>(nm.navigableKeySet(), mutex);
2903 }
2904 }
2905
2906 public NavigableSet<K> descendingKeySet() {
2907 synchronized (mutex) {
2908 return new SynchronizedNavigableSet<>(nm.descendingKeySet(), mutex);
2909 }
2910 }
2911
2912
2913 public SortedMap<K,V> subMap(K fromKey, K toKey) {
2914 synchronized (mutex) {
2915 return new SynchronizedNavigableMap<>(
2916 nm.subMap(fromKey, true, toKey, false), mutex);
2917 }
2918 }
2919 public SortedMap<K,V> headMap(K toKey) {
2920 synchronized (mutex) {
2921 return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex);
2922 }
2923 }
2924 public SortedMap<K,V> tailMap(K fromKey) {
2925 synchronized (mutex) {
2926 return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex);
2927 }
2928 }
2929
2930 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
2931 synchronized (mutex) {
2932 return new SynchronizedNavigableMap<>(
2933 nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex);
2934 }
2935 }
2936
2937 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
2938 synchronized (mutex) {
2939 return new SynchronizedNavigableMap<>(
2940 nm.headMap(toKey, inclusive), mutex);
2941 }
2942 }
2943
2944 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
2945 synchronized (mutex) {
2946 return new SynchronizedNavigableMap<>(
2947 nm.tailMap(fromKey, inclusive), mutex);
2948 }
2949 }
2950 }
2951
2952 // Dynamically typesafe collection wrappers
2953
2954 /**
2955 * Returns a dynamically typesafe view of the specified collection.
2956 * Any attempt to insert an element of the wrong type will result in an
2957 * immediate {@link ClassCastException}. Assuming a collection
2958 * contains no incorrectly typed elements prior to the time a
2959 * dynamically typesafe view is generated, and that all subsequent
2960 * access to the collection takes place through the view, it is
2961 * <i>guaranteed</i> that the collection cannot contain an incorrectly
2962 * typed element.
2963 *
2964 * <p>The generics mechanism in the language provides compile-time
2965 * (static) type checking, but it is possible to defeat this mechanism
2966 * with unchecked casts. Usually this is not a problem, as the compiler
2967 * issues warnings on all such unchecked operations. There are, however,
2968 * times when static type checking alone is not sufficient. For example,
2969 * suppose a collection is passed to a third-party library and it is
2970 * imperative that the library code not corrupt the collection by
2971 * inserting an element of the wrong type.
2972 *
2973 * <p>Another use of dynamically typesafe views is debugging. Suppose a
2974 * program fails with a {@code ClassCastException}, indicating that an
2975 * incorrectly typed element was put into a parameterized collection.
2976 * Unfortunately, the exception can occur at any time after the erroneous
2977 * element is inserted, so it typically provides little or no information
2978 * as to the real source of the problem. If the problem is reproducible,
2979 * one can quickly determine its source by temporarily modifying the
2980 * program to wrap the collection with a dynamically typesafe view.
2981 * For example, this declaration:
2982 * <pre> {@code
2983 * Collection<String> c = new HashSet<>();
2984 * }</pre>
2985 * may be replaced temporarily by this one:
2986 * <pre> {@code
2987 * Collection<String> c = Collections.checkedCollection(
2988 * new HashSet<>(), String.class);
2989 * }</pre>
2990 * Running the program again will cause it to fail at the point where
2991 * an incorrectly typed element is inserted into the collection, clearly
2992 * identifying the source of the problem. Once the problem is fixed, the
2993 * modified declaration may be reverted back to the original.
2994 *
2995 * <p>The returned collection does <i>not</i> pass the hashCode and equals
2996 * operations through to the backing collection, but relies on
2997 * {@code Object}'s {@code equals} and {@code hashCode} methods. This
2998 * is necessary to preserve the contracts of these operations in the case
2999 * that the backing collection is a set or a list.
3000 *
3001 * <p>The returned collection will be serializable if the specified
3002 * collection is serializable.
3003 *
3004 * <p>Since {@code null} is considered to be a value of any reference
3005 * type, the returned collection permits insertion of null elements
3006 * whenever the backing collection does.
3007 *
3008 * @param <E> the class of the objects in the collection
3009 * @param c the collection for which a dynamically typesafe view is to be
3010 * returned
3011 * @param type the type of element that {@code c} is permitted to hold
3012 * @return a dynamically typesafe view of the specified collection
3013 * @since 1.5
3014 */
3015 public static <E> Collection<E> checkedCollection(Collection<E> c,
3016 Class<E> type) {
3017 return new CheckedCollection<>(c, type);
3018 }
3019
3020 @SuppressWarnings("unchecked")
3021 static <T> T[] zeroLengthArray(Class<T> type) {
3022 return (T[]) Array.newInstance(type, 0);
3023 }
3024
3025 /**
3026 * @serial include
3027 */
3028 static class CheckedCollection<E> implements Collection<E>, Serializable {
3029 private static final long serialVersionUID = 1578914078182001775L;
3030
3031 final Collection<E> c;
3032 final Class<E> type;
3033
3034 @SuppressWarnings("unchecked")
3035 E typeCheck(Object o) {
3036 if (o != null && !type.isInstance(o))
3037 throw new ClassCastException(badElementMsg(o));
3038 return (E) o;
3039 }
3040
3041 private String badElementMsg(Object o) {
3042 return "Attempt to insert " + o.getClass() +
3043 " element into collection with element type " + type;
3044 }
3045
3046 CheckedCollection(Collection<E> c, Class<E> type) {
3047 this.c = Objects.requireNonNull(c, "c");
3048 this.type = Objects.requireNonNull(type, "type");
3049 }
3050
3051 public int size() { return c.size(); }
3052 public boolean isEmpty() { return c.isEmpty(); }
3053 public boolean contains(Object o) { return c.contains(o); }
3054 public Object[] toArray() { return c.toArray(); }
3055 public <T> T[] toArray(T[] a) { return c.toArray(a); }
3056 public String toString() { return c.toString(); }
3057 public boolean remove(Object o) { return c.remove(o); }
3058 public void clear() { c.clear(); }
3059
3060 public boolean containsAll(Collection<?> coll) {
3061 return c.containsAll(coll);
3062 }
3063 public boolean removeAll(Collection<?> coll) {
3064 return c.removeAll(coll);
3065 }
3066 public boolean retainAll(Collection<?> coll) {
3067 return c.retainAll(coll);
3068 }
3069
3070 public Iterator<E> iterator() {
3071 // JDK-6363904 - unwrapped iterator could be typecast to
3072 // ListIterator with unsafe set()
3073 final Iterator<E> it = c.iterator();
3074 return new Iterator<E>() {
3075 public boolean hasNext() { return it.hasNext(); }
3076 public E next() { return it.next(); }
3077 public void remove() { it.remove(); }};
3078 }
3079
3080 public boolean add(E e) { return c.add(typeCheck(e)); }
3081
3082 private E[] zeroLengthElementArray; // Lazily initialized
3083
3084 private E[] zeroLengthElementArray() {
3085 return zeroLengthElementArray != null ? zeroLengthElementArray :
3086 (zeroLengthElementArray = zeroLengthArray(type));
3087 }
3088
3089 @SuppressWarnings("unchecked")
3090 Collection<E> checkedCopyOf(Collection<? extends E> coll) {
3091 Object[] a;
3092 try {
3093 E[] z = zeroLengthElementArray();
3094 a = coll.toArray(z);
3095 // Defend against coll violating the toArray contract
3096 if (a.getClass() != z.getClass())
3097 a = Arrays.copyOf(a, a.length, z.getClass());
3098 } catch (ArrayStoreException ignore) {
3099 // To get better and consistent diagnostics,
3100 // we call typeCheck explicitly on each element.
3101 // We call clone() to defend against coll retaining a
3102 // reference to the returned array and storing a bad
3103 // element into it after it has been type checked.
3104 a = coll.toArray().clone();
3105 for (Object o : a)
3106 typeCheck(o);
3107 }
3108 // A slight abuse of the type system, but safe here.
3109 return (Collection<E>) Arrays.asList(a);
3110 }
3111
3112 public boolean addAll(Collection<? extends E> coll) {
3113 // Doing things this way insulates us from concurrent changes
3114 // in the contents of coll and provides all-or-nothing
3115 // semantics (which we wouldn't get if we type-checked each
3116 // element as we added it)
3117 return c.addAll(checkedCopyOf(coll));
3118 }
3119
3120 // Override default methods in Collection
3121 @Override
3122 public void forEach(Consumer<? super E> action) {c.forEach(action);}
3123 @Override
3124 public boolean removeIf(Predicate<? super E> filter) {
3125 return c.removeIf(filter);
3126 }
3127 @Override
3128 public Spliterator<E> spliterator() {return c.spliterator();}
3129 @Override
3130 public Stream<E> stream() {return c.stream();}
3131 @Override
3132 public Stream<E> parallelStream() {return c.parallelStream();}
3133 }
3134
3135 /**
3136 * Returns a dynamically typesafe view of the specified queue.
3137 * Any attempt to insert an element of the wrong type will result in
3138 * an immediate {@link ClassCastException}. Assuming a queue contains
3139 * no incorrectly typed elements prior to the time a dynamically typesafe
3140 * view is generated, and that all subsequent access to the queue
3141 * takes place through the view, it is <i>guaranteed</i> that the
3142 * queue cannot contain an incorrectly typed element.
3143 *
3144 * <p>A discussion of the use of dynamically typesafe views may be
3145 * found in the documentation for the {@link #checkedCollection
3146 * checkedCollection} method.
3147 *
3148 * <p>The returned queue will be serializable if the specified queue
3149 * is serializable.
3150 *
3151 * <p>Since {@code null} is considered to be a value of any reference
3152 * type, the returned queue permits insertion of {@code null} elements
3153 * whenever the backing queue does.
3154 *
3155 * @param <E> the class of the objects in the queue
3156 * @param queue the queue for which a dynamically typesafe view is to be
3157 * returned
3158 * @param type the type of element that {@code queue} is permitted to hold
3159 * @return a dynamically typesafe view of the specified queue
3160 * @since 1.8
3161 */
3162 public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) {
3163 return new CheckedQueue<>(queue, type);
3164 }
3165
3166 /**
3167 * @serial include
3168 */
3169 static class CheckedQueue<E>
3170 extends CheckedCollection<E>
3171 implements Queue<E>, Serializable
3172 {
3173 private static final long serialVersionUID = 1433151992604707767L;
3174 final Queue<E> queue;
3175
3176 CheckedQueue(Queue<E> queue, Class<E> elementType) {
3177 super(queue, elementType);
3178 this.queue = queue;
3179 }
3180
3181 public E element() {return queue.element();}
3182 public boolean equals(Object o) {return o == this || c.equals(o);}
3183 public int hashCode() {return c.hashCode();}
3184 public E peek() {return queue.peek();}
3185 public E poll() {return queue.poll();}
3186 public E remove() {return queue.remove();}
3187 public boolean offer(E e) {return queue.offer(typeCheck(e));}
3188 }
3189
3190 /**
3191 * Returns a dynamically typesafe view of the specified set.
3192 * Any attempt to insert an element of the wrong type will result in
3193 * an immediate {@link ClassCastException}. Assuming a set contains
3194 * no incorrectly typed elements prior to the time a dynamically typesafe
3195 * view is generated, and that all subsequent access to the set
3196 * takes place through the view, it is <i>guaranteed</i> that the
3197 * set cannot contain an incorrectly typed element.
3198 *
3199 * <p>A discussion of the use of dynamically typesafe views may be
3200 * found in the documentation for the {@link #checkedCollection
3201 * checkedCollection} method.
3202 *
3203 * <p>The returned set will be serializable if the specified set is
3204 * serializable.
3205 *
3206 * <p>Since {@code null} is considered to be a value of any reference
3207 * type, the returned set permits insertion of null elements whenever
3208 * the backing set does.
3209 *
3210 * @param <E> the class of the objects in the set
3211 * @param s the set for which a dynamically typesafe view is to be
3212 * returned
3213 * @param type the type of element that {@code s} is permitted to hold
3214 * @return a dynamically typesafe view of the specified set
3215 * @since 1.5
3216 */
3217 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) {
3218 return new CheckedSet<>(s, type);
3219 }
3220
3221 /**
3222 * @serial include
3223 */
3224 static class CheckedSet<E> extends CheckedCollection<E>
3225 implements Set<E>, Serializable
3226 {
3227 private static final long serialVersionUID = 4694047833775013803L;
3228
3229 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); }
3230
3231 public boolean equals(Object o) { return o == this || c.equals(o); }
3232 public int hashCode() { return c.hashCode(); }
3233 }
3234
3235 /**
3236 * Returns a dynamically typesafe view of the specified sorted set.
3237 * Any attempt to insert an element of the wrong type will result in an
3238 * immediate {@link ClassCastException}. Assuming a sorted set
3239 * contains no incorrectly typed elements prior to the time a
3240 * dynamically typesafe view is generated, and that all subsequent
3241 * access to the sorted set takes place through the view, it is
3242 * <i>guaranteed</i> that the sorted set cannot contain an incorrectly
3243 * typed element.
3244 *
3245 * <p>A discussion of the use of dynamically typesafe views may be
3246 * found in the documentation for the {@link #checkedCollection
3247 * checkedCollection} method.
3248 *
3249 * <p>The returned sorted set will be serializable if the specified sorted
3250 * set is serializable.
3251 *
3252 * <p>Since {@code null} is considered to be a value of any reference
3253 * type, the returned sorted set permits insertion of null elements
3254 * whenever the backing sorted set does.
3255 *
3256 * @param <E> the class of the objects in the set
3257 * @param s the sorted set for which a dynamically typesafe view is to be
3258 * returned
3259 * @param type the type of element that {@code s} is permitted to hold
3260 * @return a dynamically typesafe view of the specified sorted set
3261 * @since 1.5
3262 */
3263 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s,
3264 Class<E> type) {
3265 return new CheckedSortedSet<>(s, type);
3266 }
3267
3268 /**
3269 * @serial include
3270 */
3271 static class CheckedSortedSet<E> extends CheckedSet<E>
3272 implements SortedSet<E>, Serializable
3273 {
3274 private static final long serialVersionUID = 1599911165492914959L;
3275
3276 private final SortedSet<E> ss;
3277
3278 CheckedSortedSet(SortedSet<E> s, Class<E> type) {
3279 super(s, type);
3280 ss = s;
3281 }
3282
3283 public Comparator<? super E> comparator() { return ss.comparator(); }
3284 public E first() { return ss.first(); }
3285 public E last() { return ss.last(); }
3286
3287 public SortedSet<E> subSet(E fromElement, E toElement) {
3288 return checkedSortedSet(ss.subSet(fromElement,toElement), type);
3289 }
3290 public SortedSet<E> headSet(E toElement) {
3291 return checkedSortedSet(ss.headSet(toElement), type);
3292 }
3293 public SortedSet<E> tailSet(E fromElement) {
3294 return checkedSortedSet(ss.tailSet(fromElement), type);
3295 }
3296 }
3297
3298 /**
3299 * Returns a dynamically typesafe view of the specified navigable set.
3300 * Any attempt to insert an element of the wrong type will result in an
3301 * immediate {@link ClassCastException}. Assuming a navigable set
3302 * contains no incorrectly typed elements prior to the time a
3303 * dynamically typesafe view is generated, and that all subsequent
3304 * access to the navigable set takes place through the view, it is
3305 * <em>guaranteed</em> that the navigable set cannot contain an incorrectly
3306 * typed element.
3307 *
3308 * <p>A discussion of the use of dynamically typesafe views may be
3309 * found in the documentation for the {@link #checkedCollection
3310 * checkedCollection} method.
3311 *
3312 * <p>The returned navigable set will be serializable if the specified
3313 * navigable set is serializable.
3314 *
3315 * <p>Since {@code null} is considered to be a value of any reference
3316 * type, the returned navigable set permits insertion of null elements
3317 * whenever the backing sorted set does.
3318 *
3319 * @param <E> the class of the objects in the set
3320 * @param s the navigable set for which a dynamically typesafe view is to be
3321 * returned
3322 * @param type the type of element that {@code s} is permitted to hold
3323 * @return a dynamically typesafe view of the specified navigable set
3324 * @since 1.8
3325 */
3326 public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s,
3327 Class<E> type) {
3328 return new CheckedNavigableSet<>(s, type);
3329 }
3330
3331 /**
3332 * @serial include
3333 */
3334 static class CheckedNavigableSet<E> extends CheckedSortedSet<E>
3335 implements NavigableSet<E>, Serializable
3336 {
3337 private static final long serialVersionUID = -5429120189805438922L;
3338
3339 private final NavigableSet<E> ns;
3340
3341 CheckedNavigableSet(NavigableSet<E> s, Class<E> type) {
3342 super(s, type);
3343 ns = s;
3344 }
3345
3346 public E lower(E e) { return ns.lower(e); }
3347 public E floor(E e) { return ns.floor(e); }
3348 public E ceiling(E e) { return ns.ceiling(e); }
3349 public E higher(E e) { return ns.higher(e); }
3350 public E pollFirst() { return ns.pollFirst(); }
3351 public E pollLast() {return ns.pollLast(); }
3352 public NavigableSet<E> descendingSet()
3353 { return checkedNavigableSet(ns.descendingSet(), type); }
3354 public Iterator<E> descendingIterator()
3355 {return checkedNavigableSet(ns.descendingSet(), type).iterator(); }
3356
3357 public NavigableSet<E> subSet(E fromElement, E toElement) {
3358 return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type);
3359 }
3360 public NavigableSet<E> headSet(E toElement) {
3361 return checkedNavigableSet(ns.headSet(toElement, false), type);
3362 }
3363 public NavigableSet<E> tailSet(E fromElement) {
3364 return checkedNavigableSet(ns.tailSet(fromElement, true), type);
3365 }
3366
3367 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
3368 return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type);
3369 }
3370
3371 public NavigableSet<E> headSet(E toElement, boolean inclusive) {
3372 return checkedNavigableSet(ns.headSet(toElement, inclusive), type);
3373 }
3374
3375 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
3376 return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type);
3377 }
3378 }
3379
3380 /**
3381 * Returns a dynamically typesafe view of the specified list.
3382 * Any attempt to insert an element of the wrong type will result in
3383 * an immediate {@link ClassCastException}. Assuming a list contains
3384 * no incorrectly typed elements prior to the time a dynamically typesafe
3385 * view is generated, and that all subsequent access to the list
3386 * takes place through the view, it is <i>guaranteed</i> that the
3387 * list cannot contain an incorrectly typed element.
3388 *
3389 * <p>A discussion of the use of dynamically typesafe views may be
3390 * found in the documentation for the {@link #checkedCollection
3391 * checkedCollection} method.
3392 *
3393 * <p>The returned list will be serializable if the specified list
3394 * is serializable.
3395 *
3396 * <p>Since {@code null} is considered to be a value of any reference
3397 * type, the returned list permits insertion of null elements whenever
3398 * the backing list does.
3399 *
3400 * @param <E> the class of the objects in the list
3401 * @param list the list for which a dynamically typesafe view is to be
3402 * returned
3403 * @param type the type of element that {@code list} is permitted to hold
3404 * @return a dynamically typesafe view of the specified list
3405 * @since 1.5
3406 */
3407 public static <E> List<E> checkedList(List<E> list, Class<E> type) {
3408 return (list instanceof RandomAccess ?
3409 new CheckedRandomAccessList<>(list, type) :
3410 new CheckedList<>(list, type));
3411 }
3412
3413 /**
3414 * @serial include
3415 */
3416 static class CheckedList<E>
3417 extends CheckedCollection<E>
3418 implements List<E>
3419 {
3420 private static final long serialVersionUID = 65247728283967356L;
3421 final List<E> list;
3422
3423 CheckedList(List<E> list, Class<E> type) {
3424 super(list, type);
3425 this.list = list;
3426 }
3427
3428 public boolean equals(Object o) { return o == this || list.equals(o); }
3429 public int hashCode() { return list.hashCode(); }
3430 public E get(int index) { return list.get(index); }
3431 public E remove(int index) { return list.remove(index); }
3432 public int indexOf(Object o) { return list.indexOf(o); }
3433 public int lastIndexOf(Object o) { return list.lastIndexOf(o); }
3434
3435 public E set(int index, E element) {
3436 return list.set(index, typeCheck(element));
3437 }
3438
3439 public void add(int index, E element) {
3440 list.add(index, typeCheck(element));
3441 }
3442
3443 public boolean addAll(int index, Collection<? extends E> c) {
3444 return list.addAll(index, checkedCopyOf(c));
3445 }
3446 public ListIterator<E> listIterator() { return listIterator(0); }
3447
3448 public ListIterator<E> listIterator(final int index) {
3449 final ListIterator<E> i = list.listIterator(index);
3450
3451 return new ListIterator<E>() {
3452 public boolean hasNext() { return i.hasNext(); }
3453 public E next() { return i.next(); }
3454 public boolean hasPrevious() { return i.hasPrevious(); }
3455 public E previous() { return i.previous(); }
3456 public int nextIndex() { return i.nextIndex(); }
3457 public int previousIndex() { return i.previousIndex(); }
3458 public void remove() { i.remove(); }
3459
3460 public void set(E e) {
3461 i.set(typeCheck(e));
3462 }
3463
3464 public void add(E e) {
3465 i.add(typeCheck(e));
3466 }
3467
3468 @Override
3469 public void forEachRemaining(Consumer<? super E> action) {
3470 i.forEachRemaining(action);
3471 }
3472 };
3473 }
3474
3475 public List<E> subList(int fromIndex, int toIndex) {
3476 return new CheckedList<>(list.subList(fromIndex, toIndex), type);
3477 }
3478
3479 /**
3480 * {@inheritDoc}
3481 *
3482 * @throws ClassCastException if the class of an element returned by the
3483 * operator prevents it from being added to this collection. The
3484 * exception may be thrown after some elements of the list have
3485 * already been replaced.
3486 */
3487 @Override
3488 public void replaceAll(UnaryOperator<E> operator) {
3489 Objects.requireNonNull(operator);
3490 list.replaceAll(e -> typeCheck(operator.apply(e)));
3491 }
3492
3493 @Override
3494 public void sort(Comparator<? super E> c) {
3495 list.sort(c);
3496 }
3497 }
3498
3499 /**
3500 * @serial include
3501 */
3502 static class CheckedRandomAccessList<E> extends CheckedList<E>
3503 implements RandomAccess
3504 {
3505 private static final long serialVersionUID = 1638200125423088369L;
3506
3507 CheckedRandomAccessList(List<E> list, Class<E> type) {
3508 super(list, type);
3509 }
3510
3511 public List<E> subList(int fromIndex, int toIndex) {
3512 return new CheckedRandomAccessList<>(
3513 list.subList(fromIndex, toIndex), type);
3514 }
3515 }
3516
3517 /**
3518 * Returns a dynamically typesafe view of the specified map.
3519 * Any attempt to insert a mapping whose key or value have the wrong
3520 * type will result in an immediate {@link ClassCastException}.
3521 * Similarly, any attempt to modify the value currently associated with
3522 * a key will result in an immediate {@link ClassCastException},
3523 * whether the modification is attempted directly through the map
3524 * itself, or through a {@link Map.Entry} instance obtained from the
3525 * map's {@link Map#entrySet() entry set} view.
3526 *
3527 * <p>Assuming a map contains no incorrectly typed keys or values
3528 * prior to the time a dynamically typesafe view is generated, and
3529 * that all subsequent access to the map takes place through the view
3530 * (or one of its collection views), it is <i>guaranteed</i> that the
3531 * map cannot contain an incorrectly typed key or value.
3532 *
3533 * <p>A discussion of the use of dynamically typesafe views may be
3534 * found in the documentation for the {@link #checkedCollection
3535 * checkedCollection} method.
3536 *
3537 * <p>The returned map will be serializable if the specified map is
3538 * serializable.
3539 *
3540 * <p>Since {@code null} is considered to be a value of any reference
3541 * type, the returned map permits insertion of null keys or values
3542 * whenever the backing map does.
3543 *
3544 * @param <K> the class of the map keys
3545 * @param <V> the class of the map values
3546 * @param m the map for which a dynamically typesafe view is to be
3547 * returned
3548 * @param keyType the type of key that {@code m} is permitted to hold
3549 * @param valueType the type of value that {@code m} is permitted to hold
3550 * @return a dynamically typesafe view of the specified map
3551 * @since 1.5
3552 */
3553 public static <K, V> Map<K, V> checkedMap(Map<K, V> m,
3554 Class<K> keyType,
3555 Class<V> valueType) {
3556 return new CheckedMap<>(m, keyType, valueType);
3557 }
3558
3559
3560 /**
3561 * @serial include
3562 */
3563 private static class CheckedMap<K,V>
3564 implements Map<K,V>, Serializable
3565 {
3566 private static final long serialVersionUID = 5742860141034234728L;
3567
3568 private final Map<K, V> m;
3569 final Class<K> keyType;
3570 final Class<V> valueType;
3571
3572 private void typeCheck(Object key, Object value) {
3573 if (key != null && !keyType.isInstance(key))
3574 throw new ClassCastException(badKeyMsg(key));
3575
3576 if (value != null && !valueType.isInstance(value))
3577 throw new ClassCastException(badValueMsg(value));
3578 }
3579
3580 private BiFunction<? super K, ? super V, ? extends V> typeCheck(
3581 BiFunction<? super K, ? super V, ? extends V> func) {
3582 Objects.requireNonNull(func);
3583 return (k, v) -> {
3584 V newValue = func.apply(k, v);
3585 typeCheck(k, newValue);
3586 return newValue;
3587 };
3588 }
3589
3590 private String badKeyMsg(Object key) {
3591 return "Attempt to insert " + key.getClass() +
3592 " key into map with key type " + keyType;
3593 }
3594
3595 private String badValueMsg(Object value) {
3596 return "Attempt to insert " + value.getClass() +
3597 " value into map with value type " + valueType;
3598 }
3599
3600 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) {
3601 this.m = Objects.requireNonNull(m);
3602 this.keyType = Objects.requireNonNull(keyType);
3603 this.valueType = Objects.requireNonNull(valueType);
3604 }
3605
3606 public int size() { return m.size(); }
3607 public boolean isEmpty() { return m.isEmpty(); }
3608 public boolean containsKey(Object key) { return m.containsKey(key); }
3609 public boolean containsValue(Object v) { return m.containsValue(v); }
3610 public V get(Object key) { return m.get(key); }
3611 public V remove(Object key) { return m.remove(key); }
3612 public void clear() { m.clear(); }
3613 public Set<K> keySet() { return m.keySet(); }
3614 public Collection<V> values() { return m.values(); }
3615 public boolean equals(Object o) { return o == this || m.equals(o); }
3616 public int hashCode() { return m.hashCode(); }
3617 public String toString() { return m.toString(); }
3618
3619 public V put(K key, V value) {
3620 typeCheck(key, value);
3621 return m.put(key, value);
3622 }
3623
3624 @SuppressWarnings("unchecked")
3625 public void putAll(Map<? extends K, ? extends V> t) {
3626 // Satisfy the following goals:
3627 // - good diagnostics in case of type mismatch
3628 // - all-or-nothing semantics
3629 // - protection from malicious t
3630 // - correct behavior if t is a concurrent map
3631 Object[] entries = t.entrySet().toArray();
3632 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length);
3633 for (Object o : entries) {
3634 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3635 Object k = e.getKey();
3636 Object v = e.getValue();
3637 typeCheck(k, v);
3638 checked.add(
3639 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v));
3640 }
3641 for (Map.Entry<K,V> e : checked)
3642 m.put(e.getKey(), e.getValue());
3643 }
3644
3645 private transient Set<Map.Entry<K,V>> entrySet;
3646
3647 public Set<Map.Entry<K,V>> entrySet() {
3648 if (entrySet==null)
3649 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType);
3650 return entrySet;
3651 }
3652
3653 // Override default methods in Map
3654 @Override
3655 public void forEach(BiConsumer<? super K, ? super V> action) {
3656 m.forEach(action);
3657 }
3658
3659 @Override
3660 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
3661 m.replaceAll(typeCheck(function));
3662 }
3663
3664 @Override
3665 public V putIfAbsent(K key, V value) {
3666 typeCheck(key, value);
3667 return m.putIfAbsent(key, value);
3668 }
3669
3670 @Override
3671 public boolean remove(Object key, Object value) {
3672 return m.remove(key, value);
3673 }
3674
3675 @Override
3676 public boolean replace(K key, V oldValue, V newValue) {
3677 typeCheck(key, newValue);
3678 return m.replace(key, oldValue, newValue);
3679 }
3680
3681 @Override
3682 public V replace(K key, V value) {
3683 typeCheck(key, value);
3684 return m.replace(key, value);
3685 }
3686
3687 @Override
3688 public V computeIfAbsent(K key,
3689 Function<? super K, ? extends V> mappingFunction) {
3690 Objects.requireNonNull(mappingFunction);
3691 return m.computeIfAbsent(key, k -> {
3692 V value = mappingFunction.apply(k);
3693 typeCheck(k, value);
3694 return value;
3695 });
3696 }
3697
3698 @Override
3699 public V computeIfPresent(K key,
3700 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3701 return m.computeIfPresent(key, typeCheck(remappingFunction));
3702 }
3703
3704 @Override
3705 public V compute(K key,
3706 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
3707 return m.compute(key, typeCheck(remappingFunction));
3708 }
3709
3710 @Override
3711 public V merge(K key, V value,
3712 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
3713 Objects.requireNonNull(remappingFunction);
3714 return m.merge(key, value, (v1, v2) -> {
3715 V newValue = remappingFunction.apply(v1, v2);
3716 typeCheck(null, newValue);
3717 return newValue;
3718 });
3719 }
3720
3721 /**
3722 * We need this class in addition to CheckedSet as Map.Entry permits
3723 * modification of the backing Map via the setValue operation. This
3724 * class is subtle: there are many possible attacks that must be
3725 * thwarted.
3726 *
3727 * @serial exclude
3728 */
3729 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> {
3730 private final Set<Map.Entry<K,V>> s;
3731 private final Class<V> valueType;
3732
3733 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) {
3734 this.s = s;
3735 this.valueType = valueType;
3736 }
3737
3738 public int size() { return s.size(); }
3739 public boolean isEmpty() { return s.isEmpty(); }
3740 public String toString() { return s.toString(); }
3741 public int hashCode() { return s.hashCode(); }
3742 public void clear() { s.clear(); }
3743
3744 public boolean add(Map.Entry<K, V> e) {
3745 throw new UnsupportedOperationException();
3746 }
3747 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) {
3748 throw new UnsupportedOperationException();
3749 }
3750
3751 public Iterator<Map.Entry<K,V>> iterator() {
3752 final Iterator<Map.Entry<K, V>> i = s.iterator();
3753 final Class<V> valueType = this.valueType;
3754
3755 return new Iterator<Map.Entry<K,V>>() {
3756 public boolean hasNext() { return i.hasNext(); }
3757 public void remove() { i.remove(); }
3758
3759 public Map.Entry<K,V> next() {
3760 return checkedEntry(i.next(), valueType);
3761 }
3762 };
3763 }
3764
3765 @SuppressWarnings("unchecked")
3766 public Object[] toArray() {
3767 Object[] source = s.toArray();
3768
3769 /*
3770 * Ensure that we don't get an ArrayStoreException even if
3771 * s.toArray returns an array of something other than Object
3772 */
3773 Object[] dest = (CheckedEntry.class.isInstance(
3774 source.getClass().getComponentType()) ? source :
3775 new Object[source.length]);
3776
3777 for (int i = 0; i < source.length; i++)
3778 dest[i] = checkedEntry((Map.Entry<K,V>)source[i],
3779 valueType);
3780 return dest;
3781 }
3782
3783 @SuppressWarnings("unchecked")
3784 public <T> T[] toArray(T[] a) {
3785 // We don't pass a to s.toArray, to avoid window of
3786 // vulnerability wherein an unscrupulous multithreaded client
3787 // could get his hands on raw (unwrapped) Entries from s.
3788 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0));
3789
3790 for (int i=0; i<arr.length; i++)
3791 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i],
3792 valueType);
3793 if (arr.length > a.length)
3794 return arr;
3795
3796 System.arraycopy(arr, 0, a, 0, arr.length);
3797 if (a.length > arr.length)
3798 a[arr.length] = null;
3799 return a;
3800 }
3801
3802 /**
3803 * This method is overridden to protect the backing set against
3804 * an object with a nefarious equals function that senses
3805 * that the equality-candidate is Map.Entry and calls its
3806 * setValue method.
3807 */
3808 public boolean contains(Object o) {
3809 if (!(o instanceof Map.Entry))
3810 return false;
3811 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
3812 return s.contains(
3813 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType));
3814 }
3815
3816 /**
3817 * The bulk collection methods are overridden to protect
3818 * against an unscrupulous collection whose contains(Object o)
3819 * method senses when o is a Map.Entry, and calls o.setValue.
3820 */
3821 public boolean containsAll(Collection<?> c) {
3822 for (Object o : c)
3823 if (!contains(o)) // Invokes safe contains() above
3824 return false;
3825 return true;
3826 }
3827
3828 public boolean remove(Object o) {
3829 if (!(o instanceof Map.Entry))
3830 return false;
3831 return s.remove(new AbstractMap.SimpleImmutableEntry
3832 <>((Map.Entry<?,?>)o));
3833 }
3834
3835 public boolean removeAll(Collection<?> c) {
3836 return batchRemove(c, false);
3837 }
3838 public boolean retainAll(Collection<?> c) {
3839 return batchRemove(c, true);
3840 }
3841 private boolean batchRemove(Collection<?> c, boolean complement) {
3842 Objects.requireNonNull(c);
3843 boolean modified = false;
3844 Iterator<Map.Entry<K,V>> it = iterator();
3845 while (it.hasNext()) {
3846 if (c.contains(it.next()) != complement) {
3847 it.remove();
3848 modified = true;
3849 }
3850 }
3851 return modified;
3852 }
3853
3854 public boolean equals(Object o) {
3855 if (o == this)
3856 return true;
3857 if (!(o instanceof Set))
3858 return false;
3859 Set<?> that = (Set<?>) o;
3860 return that.size() == s.size()
3861 && containsAll(that); // Invokes safe containsAll() above
3862 }
3863
3864 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e,
3865 Class<T> valueType) {
3866 return new CheckedEntry<>(e, valueType);
3867 }
3868
3869 /**
3870 * This "wrapper class" serves two purposes: it prevents
3871 * the client from modifying the backing Map, by short-circuiting
3872 * the setValue method, and it protects the backing Map against
3873 * an ill-behaved Map.Entry that attempts to modify another
3874 * Map.Entry when asked to perform an equality check.
3875 */
3876 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> {
3877 private final Map.Entry<K, V> e;
3878 private final Class<T> valueType;
3879
3880 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) {
3881 this.e = Objects.requireNonNull(e);
3882 this.valueType = Objects.requireNonNull(valueType);
3883 }
3884
3885 public K getKey() { return e.getKey(); }
3886 public V getValue() { return e.getValue(); }
3887 public int hashCode() { return e.hashCode(); }
3888 public String toString() { return e.toString(); }
3889
3890 public V setValue(V value) {
3891 if (value != null && !valueType.isInstance(value))
3892 throw new ClassCastException(badValueMsg(value));
3893 return e.setValue(value);
3894 }
3895
3896 private String badValueMsg(Object value) {
3897 return "Attempt to insert " + value.getClass() +
3898 " value into map with value type " + valueType;
3899 }
3900
3901 public boolean equals(Object o) {
3902 if (o == this)
3903 return true;
3904 if (!(o instanceof Map.Entry))
3905 return false;
3906 return e.equals(new AbstractMap.SimpleImmutableEntry
3907 <>((Map.Entry<?,?>)o));
3908 }
3909 }
3910 }
3911 }
3912
3913 /**
3914 * Returns a dynamically typesafe view of the specified sorted map.
3915 * Any attempt to insert a mapping whose key or value have the wrong
3916 * type will result in an immediate {@link ClassCastException}.
3917 * Similarly, any attempt to modify the value currently associated with
3918 * a key will result in an immediate {@link ClassCastException},
3919 * whether the modification is attempted directly through the map
3920 * itself, or through a {@link Map.Entry} instance obtained from the
3921 * map's {@link Map#entrySet() entry set} view.
3922 *
3923 * <p>Assuming a map contains no incorrectly typed keys or values
3924 * prior to the time a dynamically typesafe view is generated, and
3925 * that all subsequent access to the map takes place through the view
3926 * (or one of its collection views), it is <i>guaranteed</i> that the
3927 * map cannot contain an incorrectly typed key or value.
3928 *
3929 * <p>A discussion of the use of dynamically typesafe views may be
3930 * found in the documentation for the {@link #checkedCollection
3931 * checkedCollection} method.
3932 *
3933 * <p>The returned map will be serializable if the specified map is
3934 * serializable.
3935 *
3936 * <p>Since {@code null} is considered to be a value of any reference
3937 * type, the returned map permits insertion of null keys or values
3938 * whenever the backing map does.
3939 *
3940 * @param <K> the class of the map keys
3941 * @param <V> the class of the map values
3942 * @param m the map for which a dynamically typesafe view is to be
3943 * returned
3944 * @param keyType the type of key that {@code m} is permitted to hold
3945 * @param valueType the type of value that {@code m} is permitted to hold
3946 * @return a dynamically typesafe view of the specified map
3947 * @since 1.5
3948 */
3949 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m,
3950 Class<K> keyType,
3951 Class<V> valueType) {
3952 return new CheckedSortedMap<>(m, keyType, valueType);
3953 }
3954
3955 /**
3956 * @serial include
3957 */
3958 static class CheckedSortedMap<K,V> extends CheckedMap<K,V>
3959 implements SortedMap<K,V>, Serializable
3960 {
3961 private static final long serialVersionUID = 1599671320688067438L;
3962
3963 private final SortedMap<K, V> sm;
3964
3965 CheckedSortedMap(SortedMap<K, V> m,
3966 Class<K> keyType, Class<V> valueType) {
3967 super(m, keyType, valueType);
3968 sm = m;
3969 }
3970
3971 public Comparator<? super K> comparator() { return sm.comparator(); }
3972 public K firstKey() { return sm.firstKey(); }
3973 public K lastKey() { return sm.lastKey(); }
3974
3975 public SortedMap<K,V> subMap(K fromKey, K toKey) {
3976 return checkedSortedMap(sm.subMap(fromKey, toKey),
3977 keyType, valueType);
3978 }
3979 public SortedMap<K,V> headMap(K toKey) {
3980 return checkedSortedMap(sm.headMap(toKey), keyType, valueType);
3981 }
3982 public SortedMap<K,V> tailMap(K fromKey) {
3983 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType);
3984 }
3985 }
3986
3987 /**
3988 * Returns a dynamically typesafe view of the specified navigable map.
3989 * Any attempt to insert a mapping whose key or value have the wrong
3990 * type will result in an immediate {@link ClassCastException}.
3991 * Similarly, any attempt to modify the value currently associated with
3992 * a key will result in an immediate {@link ClassCastException},
3993 * whether the modification is attempted directly through the map
3994 * itself, or through a {@link Map.Entry} instance obtained from the
3995 * map's {@link Map#entrySet() entry set} view.
3996 *
3997 * <p>Assuming a map contains no incorrectly typed keys or values
3998 * prior to the time a dynamically typesafe view is generated, and
3999 * that all subsequent access to the map takes place through the view
4000 * (or one of its collection views), it is <em>guaranteed</em> that the
4001 * map cannot contain an incorrectly typed key or value.
4002 *
4003 * <p>A discussion of the use of dynamically typesafe views may be
4004 * found in the documentation for the {@link #checkedCollection
4005 * checkedCollection} method.
4006 *
4007 * <p>The returned map will be serializable if the specified map is
4008 * serializable.
4009 *
4010 * <p>Since {@code null} is considered to be a value of any reference
4011 * type, the returned map permits insertion of null keys or values
4012 * whenever the backing map does.
4013 *
4014 * @param <K> type of map keys
4015 * @param <V> type of map values
4016 * @param m the map for which a dynamically typesafe view is to be
4017 * returned
4018 * @param keyType the type of key that {@code m} is permitted to hold
4019 * @param valueType the type of value that {@code m} is permitted to hold
4020 * @return a dynamically typesafe view of the specified map
4021 * @since 1.8
4022 */
4023 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m,
4024 Class<K> keyType,
4025 Class<V> valueType) {
4026 return new CheckedNavigableMap<>(m, keyType, valueType);
4027 }
4028
4029 /**
4030 * @serial include
4031 */
4032 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V>
4033 implements NavigableMap<K,V>, Serializable
4034 {
4035 private static final long serialVersionUID = -4852462692372534096L;
4036
4037 private final NavigableMap<K, V> nm;
4038
4039 CheckedNavigableMap(NavigableMap<K, V> m,
4040 Class<K> keyType, Class<V> valueType) {
4041 super(m, keyType, valueType);
4042 nm = m;
4043 }
4044
4045 public Comparator<? super K> comparator() { return nm.comparator(); }
4046 public K firstKey() { return nm.firstKey(); }
4047 public K lastKey() { return nm.lastKey(); }
4048
4049 public Entry<K, V> lowerEntry(K key) {
4050 Entry<K,V> lower = nm.lowerEntry(key);
4051 return (null != lower)
4052 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(lower, valueType)
4053 : null;
4054 }
4055
4056 public K lowerKey(K key) { return nm.lowerKey(key); }
4057
4058 public Entry<K, V> floorEntry(K key) {
4059 Entry<K,V> floor = nm.floorEntry(key);
4060 return (null != floor)
4061 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(floor, valueType)
4062 : null;
4063 }
4064
4065 public K floorKey(K key) { return nm.floorKey(key); }
4066
4067 public Entry<K, V> ceilingEntry(K key) {
4068 Entry<K,V> ceiling = nm.ceilingEntry(key);
4069 return (null != ceiling)
4070 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(ceiling, valueType)
4071 : null;
4072 }
4073
4074 public K ceilingKey(K key) { return nm.ceilingKey(key); }
4075
4076 public Entry<K, V> higherEntry(K key) {
4077 Entry<K,V> higher = nm.higherEntry(key);
4078 return (null != higher)
4079 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(higher, valueType)
4080 : null;
4081 }
4082
4083 public K higherKey(K key) { return nm.higherKey(key); }
4084
4085 public Entry<K, V> firstEntry() {
4086 Entry<K,V> first = nm.firstEntry();
4087 return (null != first)
4088 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(first, valueType)
4089 : null;
4090 }
4091
4092 public Entry<K, V> lastEntry() {
4093 Entry<K,V> last = nm.lastEntry();
4094 return (null != last)
4095 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(last, valueType)
4096 : null;
4097 }
4098
4099 public Entry<K, V> pollFirstEntry() {
4100 Entry<K,V> entry = nm.pollFirstEntry();
4101 return (null == entry)
4102 ? null
4103 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType);
4104 }
4105
4106 public Entry<K, V> pollLastEntry() {
4107 Entry<K,V> entry = nm.pollLastEntry();
4108 return (null == entry)
4109 ? null
4110 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType);
4111 }
4112
4113 public NavigableMap<K, V> descendingMap() {
4114 return checkedNavigableMap(nm.descendingMap(), keyType, valueType);
4115 }
4116
4117 public NavigableSet<K> keySet() {
4118 return navigableKeySet();
4119 }
4120
4121 public NavigableSet<K> navigableKeySet() {
4122 return checkedNavigableSet(nm.navigableKeySet(), keyType);
4123 }
4124
4125 public NavigableSet<K> descendingKeySet() {
4126 return checkedNavigableSet(nm.descendingKeySet(), keyType);
4127 }
4128
4129 @Override
4130 public NavigableMap<K,V> subMap(K fromKey, K toKey) {
4131 return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false),
4132 keyType, valueType);
4133 }
4134
4135 @Override
4136 public NavigableMap<K,V> headMap(K toKey) {
4137 return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType);
4138 }
4139
4140 @Override
4141 public NavigableMap<K,V> tailMap(K fromKey) {
4142 return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType);
4143 }
4144
4145 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
4146 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType);
4147 }
4148
4149 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) {
4150 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType);
4151 }
4152
4153 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) {
4154 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType);
4155 }
4156 }
4157
4158 // Empty collections
4159
4160 /**
4161 * Returns an iterator that has no elements. More precisely,
4162 *
4163 * <ul>
4164 * <li>{@link Iterator#hasNext hasNext} always returns {@code
4165 * false}.</li>
4166 * <li>{@link Iterator#next next} always throws {@link
4167 * NoSuchElementException}.</li>
4168 * <li>{@link Iterator#remove remove} always throws {@link
4169 * IllegalStateException}.</li>
4170 * </ul>
4171 *
4172 * <p>Implementations of this method are permitted, but not
4173 * required, to return the same object from multiple invocations.
4174 *
4175 * @param <T> type of elements, if there were any, in the iterator
4176 * @return an empty iterator
4177 * @since 1.7
4178 */
4179 @SuppressWarnings("unchecked")
4180 public static <T> Iterator<T> emptyIterator() {
4181 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR;
4182 }
4183
4184 private static class EmptyIterator<E> implements Iterator<E> {
4185 static final EmptyIterator<Object> EMPTY_ITERATOR
4186 = new EmptyIterator<>();
4187
4188 public boolean hasNext() { return false; }
4189 public E next() { throw new NoSuchElementException(); }
4190 public void remove() { throw new IllegalStateException(); }
4191 @Override
4192 public void forEachRemaining(Consumer<? super E> action) {
4193 Objects.requireNonNull(action);
4194 }
4195 }
4196
4197 /**
4198 * Returns a list iterator that has no elements. More precisely,
4199 *
4200 * <ul>
4201 * <li>{@link Iterator#hasNext hasNext} and {@link
4202 * ListIterator#hasPrevious hasPrevious} always return {@code
4203 * false}.</li>
4204 * <li>{@link Iterator#next next} and {@link ListIterator#previous
4205 * previous} always throw {@link NoSuchElementException}.</li>
4206 * <li>{@link Iterator#remove remove} and {@link ListIterator#set
4207 * set} always throw {@link IllegalStateException}.</li>
4208 * <li>{@link ListIterator#add add} always throws {@link
4209 * UnsupportedOperationException}.</li>
4210 * <li>{@link ListIterator#nextIndex nextIndex} always returns
4211 * {@code 0}.</li>
4212 * <li>{@link ListIterator#previousIndex previousIndex} always
4213 * returns {@code -1}.</li>
4214 * </ul>
4215 *
4216 * <p>Implementations of this method are permitted, but not
4217 * required, to return the same object from multiple invocations.
4218 *
4219 * @param <T> type of elements, if there were any, in the iterator
4220 * @return an empty list iterator
4221 * @since 1.7
4222 */
4223 @SuppressWarnings("unchecked")
4224 public static <T> ListIterator<T> emptyListIterator() {
4225 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR;
4226 }
4227
4228 private static class EmptyListIterator<E>
4229 extends EmptyIterator<E>
4230 implements ListIterator<E>
4231 {
4232 static final EmptyListIterator<Object> EMPTY_ITERATOR
4233 = new EmptyListIterator<>();
4234
4235 public boolean hasPrevious() { return false; }
4236 public E previous() { throw new NoSuchElementException(); }
4237 public int nextIndex() { return 0; }
4238 public int previousIndex() { return -1; }
4239 public void set(E e) { throw new IllegalStateException(); }
4240 public void add(E e) { throw new UnsupportedOperationException(); }
4241 }
4242
4243 /**
4244 * Returns an enumeration that has no elements. More precisely,
4245 *
4246 * <ul>
4247 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always
4248 * returns {@code false}.</li>
4249 * <li> {@link Enumeration#nextElement nextElement} always throws
4250 * {@link NoSuchElementException}.</li>
4251 * </ul>
4252 *
4253 * <p>Implementations of this method are permitted, but not
4254 * required, to return the same object from multiple invocations.
4255 *
4256 * @param <T> the class of the objects in the enumeration
4257 * @return an empty enumeration
4258 * @since 1.7
4259 */
4260 @SuppressWarnings("unchecked")
4261 public static <T> Enumeration<T> emptyEnumeration() {
4262 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION;
4263 }
4264
4265 private static class EmptyEnumeration<E> implements Enumeration<E> {
4266 static final EmptyEnumeration<Object> EMPTY_ENUMERATION
4267 = new EmptyEnumeration<>();
4268
4269 public boolean hasMoreElements() { return false; }
4270 public E nextElement() { throw new NoSuchElementException(); }
4271 public Iterator<E> asIterator() { return emptyIterator(); }
4272 }
4273
4274 /**
4275 * The empty set (immutable). This set is serializable.
4276 *
4277 * @see #emptySet()
4278 */
4279 @SuppressWarnings("rawtypes")
4280 public static final Set EMPTY_SET = new EmptySet<>();
4281
4282 /**
4283 * Returns an empty set (immutable). This set is serializable.
4284 * Unlike the like-named field, this method is parameterized.
4285 *
4286 * <p>This example illustrates the type-safe way to obtain an empty set:
4287 * <pre>
4288 * Set<String> s = Collections.emptySet();
4289 * </pre>
4290 * @implNote Implementations of this method need not create a separate
4291 * {@code Set} object for each call. Using this method is likely to have
4292 * comparable cost to using the like-named field. (Unlike this method, the
4293 * field does not provide type safety.)
4294 *
4295 * @param <T> the class of the objects in the set
4296 * @return the empty set
4297 *
4298 * @see #EMPTY_SET
4299 * @since 1.5
4300 */
4301 @SuppressWarnings("unchecked")
4302 public static final <T> Set<T> emptySet() {
4303 return (Set<T>) EMPTY_SET;
4304 }
4305
4306 /**
4307 * @serial include
4308 */
4309 private static class EmptySet<E>
4310 extends AbstractSet<E>
4311 implements Serializable
4312 {
4313 private static final long serialVersionUID = 1582296315990362920L;
4314
4315 public Iterator<E> iterator() { return emptyIterator(); }
4316
4317 public int size() {return 0;}
4318 public boolean isEmpty() {return true;}
4319 public void clear() {}
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 @Override
4351 public int hashCode() {
4352 return 0;
4353 }
4354 }
4355
4356 /**
4357 * Returns an empty sorted set (immutable). This set is serializable.
4358 *
4359 * <p>This example illustrates the type-safe way to obtain an empty
4360 * sorted set:
4361 * <pre> {@code
4362 * SortedSet<String> s = Collections.emptySortedSet();
4363 * }</pre>
4364 *
4365 * @implNote Implementations of this method need not create a separate
4366 * {@code SortedSet} object for each call.
4367 *
4368 * @param <E> type of elements, if there were any, in the set
4369 * @return the empty sorted set
4370 * @since 1.8
4371 */
4372 @SuppressWarnings("unchecked")
4373 public static <E> SortedSet<E> emptySortedSet() {
4374 return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
4375 }
4376
4377 /**
4378 * Returns an empty navigable set (immutable). This set is serializable.
4379 *
4380 * <p>This example illustrates the type-safe way to obtain an empty
4381 * navigable set:
4382 * <pre> {@code
4383 * NavigableSet<String> s = Collections.emptyNavigableSet();
4384 * }</pre>
4385 *
4386 * @implNote Implementations of this method need not
4387 * create a separate {@code NavigableSet} object for each call.
4388 *
4389 * @param <E> type of elements, if there were any, in the set
4390 * @return the empty navigable set
4391 * @since 1.8
4392 */
4393 @SuppressWarnings("unchecked")
4394 public static <E> NavigableSet<E> emptyNavigableSet() {
4395 return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET;
4396 }
4397
4398 /**
4399 * The empty list (immutable). This list is serializable.
4400 *
4401 * @see #emptyList()
4402 */
4403 @SuppressWarnings("rawtypes")
4404 public static final List EMPTY_LIST = new EmptyList<>();
4405
4406 /**
4407 * Returns an empty list (immutable). This list is serializable.
4408 *
4409 * <p>This example illustrates the type-safe way to obtain an empty list:
4410 * <pre>
4411 * List<String> s = Collections.emptyList();
4412 * </pre>
4413 *
4414 * @implNote
4415 * Implementations of this method need not create a separate {@code List}
4416 * object for each call. Using this method is likely to have comparable
4417 * cost to using the like-named field. (Unlike this method, the field does
4418 * not provide type safety.)
4419 *
4420 * @param <T> type of elements, if there were any, in the list
4421 * @return an empty immutable list
4422 *
4423 * @see #EMPTY_LIST
4424 * @since 1.5
4425 */
4426 @SuppressWarnings("unchecked")
4427 public static final <T> List<T> emptyList() {
4428 return (List<T>) EMPTY_LIST;
4429 }
4430
4431 /**
4432 * @serial include
4433 */
4434 private static class EmptyList<E>
4435 extends AbstractList<E>
4436 implements RandomAccess, Serializable {
4437 private static final long serialVersionUID = 8842843931221139166L;
4438
4439 public Iterator<E> iterator() {
4440 return emptyIterator();
4441 }
4442 public ListIterator<E> listIterator() {
4443 return emptyListIterator();
4444 }
4445
4446 public int size() {return 0;}
4447 public boolean isEmpty() {return true;}
4448 public void clear() {}
4449
4450 public boolean contains(Object obj) {return false;}
4451 public boolean containsAll(Collection<?> c) { return c.isEmpty(); }
4452
4453 public Object[] toArray() { return new Object[0]; }
4454
4455 public <T> T[] toArray(T[] a) {
4456 if (a.length > 0)
4457 a[0] = null;
4458 return a;
4459 }
4460
4461 public E get(int index) {
4462 throw new IndexOutOfBoundsException("Index: "+index);
4463 }
4464
4465 public boolean equals(Object o) {
4466 return (o instanceof List) && ((List<?>)o).isEmpty();
4467 }
4468
4469 public int hashCode() { return 1; }
4470
4471 @Override
4472 public boolean removeIf(Predicate<? super E> filter) {
4473 Objects.requireNonNull(filter);
4474 return false;
4475 }
4476 @Override
4477 public void replaceAll(UnaryOperator<E> operator) {
4478 Objects.requireNonNull(operator);
4479 }
4480 @Override
4481 public void sort(Comparator<? super E> c) {
4482 }
4483
4484 // Override default methods in Collection
4485 @Override
4486 public void forEach(Consumer<? super E> action) {
4487 Objects.requireNonNull(action);
4488 }
4489
4490 @Override
4491 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); }
4492
4493 // Preserves singleton property
4494 private Object readResolve() {
4495 return EMPTY_LIST;
4496 }
4497 }
4498
4499 /**
4500 * The empty map (immutable). This map is serializable.
4501 *
4502 * @see #emptyMap()
4503 * @since 1.3
4504 */
4505 @SuppressWarnings("rawtypes")
4506 public static final Map EMPTY_MAP = new EmptyMap<>();
4507
4508 /**
4509 * Returns an empty map (immutable). This map is serializable.
4510 *
4511 * <p>This example illustrates the type-safe way to obtain an empty map:
4512 * <pre>
4513 * Map<String, Date> s = Collections.emptyMap();
4514 * </pre>
4515 * @implNote Implementations of this method need not create a separate
4516 * {@code Map} object for each call. Using this method is likely to have
4517 * comparable cost to using the like-named field. (Unlike this method, the
4518 * field does not provide type safety.)
4519 *
4520 * @param <K> the class of the map keys
4521 * @param <V> the class of the map values
4522 * @return an empty map
4523 * @see #EMPTY_MAP
4524 * @since 1.5
4525 */
4526 @SuppressWarnings("unchecked")
4527 public static final <K,V> Map<K,V> emptyMap() {
4528 return (Map<K,V>) EMPTY_MAP;
4529 }
4530
4531 /**
4532 * Returns an empty sorted map (immutable). This map is serializable.
4533 *
4534 * <p>This example illustrates the type-safe way to obtain an empty map:
4535 * <pre> {@code
4536 * SortedMap<String, Date> s = Collections.emptySortedMap();
4537 * }</pre>
4538 *
4539 * @implNote Implementations of this method need not create a separate
4540 * {@code SortedMap} object for each call.
4541 *
4542 * @param <K> the class of the map keys
4543 * @param <V> the class of the map values
4544 * @return an empty sorted map
4545 * @since 1.8
4546 */
4547 @SuppressWarnings("unchecked")
4548 public static final <K,V> SortedMap<K,V> emptySortedMap() {
4549 return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
4550 }
4551
4552 /**
4553 * Returns an empty navigable map (immutable). This map is serializable.
4554 *
4555 * <p>This example illustrates the type-safe way to obtain an empty map:
4556 * <pre> {@code
4557 * NavigableMap<String, Date> s = Collections.emptyNavigableMap();
4558 * }</pre>
4559 *
4560 * @implNote Implementations of this method need not create a separate
4561 * {@code NavigableMap} object for each call.
4562 *
4563 * @param <K> the class of the map keys
4564 * @param <V> the class of the map values
4565 * @return an empty navigable map
4566 * @since 1.8
4567 */
4568 @SuppressWarnings("unchecked")
4569 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() {
4570 return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP;
4571 }
4572
4573 /**
4574 * @serial include
4575 */
4576 private static class EmptyMap<K,V>
4577 extends AbstractMap<K,V>
4578 implements Serializable
4579 {
4580 private static final long serialVersionUID = 6428348081105594320L;
4581
4582 public int size() {return 0;}
4583 public boolean isEmpty() {return true;}
4584 public void clear() {}
4585 public boolean containsKey(Object key) {return false;}
4586 public boolean containsValue(Object value) {return false;}
4587 public V get(Object key) {return null;}
4588 public Set<K> keySet() {return emptySet();}
4589 public Collection<V> values() {return emptySet();}
4590 public Set<Map.Entry<K,V>> entrySet() {return emptySet();}
4591
4592 public boolean equals(Object o) {
4593 return (o instanceof Map) && ((Map<?,?>)o).isEmpty();
4594 }
4595
4596 public int hashCode() {return 0;}
4597
4598 // Override default methods in Map
4599 @Override
4600 @SuppressWarnings("unchecked")
4601 public V getOrDefault(Object k, V defaultValue) {
4602 return defaultValue;
4603 }
4604
4605 @Override
4606 public void forEach(BiConsumer<? super K, ? super V> action) {
4607 Objects.requireNonNull(action);
4608 }
4609
4610 @Override
4611 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4612 Objects.requireNonNull(function);
4613 }
4614
4615 @Override
4616 public V putIfAbsent(K key, V value) {
4617 throw new UnsupportedOperationException();
4618 }
4619
4620 @Override
4621 public boolean remove(Object key, Object value) {
4622 throw new UnsupportedOperationException();
4623 }
4624
4625 @Override
4626 public boolean replace(K key, V oldValue, V newValue) {
4627 throw new UnsupportedOperationException();
4628 }
4629
4630 @Override
4631 public V replace(K key, V value) {
4632 throw new UnsupportedOperationException();
4633 }
4634
4635 @Override
4636 public V computeIfAbsent(K key,
4637 Function<? super K, ? extends V> mappingFunction) {
4638 throw new UnsupportedOperationException();
4639 }
4640
4641 @Override
4642 public V computeIfPresent(K key,
4643 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4644 throw new UnsupportedOperationException();
4645 }
4646
4647 @Override
4648 public V compute(K key,
4649 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4650 throw new UnsupportedOperationException();
4651 }
4652
4653 @Override
4654 public V merge(K key, V value,
4655 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4656 throw new UnsupportedOperationException();
4657 }
4658
4659 // Preserves singleton property
4660 private Object readResolve() {
4661 return EMPTY_MAP;
4662 }
4663 }
4664
4665 // Singleton collections
4666
4667 /**
4668 * Returns an immutable set containing only the specified object.
4669 * The returned set is serializable.
4670 *
4671 * @param <T> the class of the objects in the set
4672 * @param o the sole object to be stored in the returned set.
4673 * @return an immutable set containing only the specified object.
4674 */
4675 public static <T> Set<T> singleton(T o) {
4676 return new SingletonSet<>(o);
4677 }
4678
4679 static <E> Iterator<E> singletonIterator(final E e) {
4680 return new Iterator<E>() {
4681 private boolean hasNext = true;
4682 public boolean hasNext() {
4683 return hasNext;
4684 }
4685 public E next() {
4686 if (hasNext) {
4687 hasNext = false;
4688 return e;
4689 }
4690 throw new NoSuchElementException();
4691 }
4692 public void remove() {
4693 throw new UnsupportedOperationException();
4694 }
4695 @Override
4696 public void forEachRemaining(Consumer<? super E> action) {
4697 Objects.requireNonNull(action);
4698 if (hasNext) {
4699 hasNext = false;
4700 action.accept(e);
4701 }
4702 }
4703 };
4704 }
4705
4706 /**
4707 * Creates a {@code Spliterator} with only the specified element
4708 *
4709 * @param <T> Type of elements
4710 * @return A singleton {@code Spliterator}
4711 */
4712 static <T> Spliterator<T> singletonSpliterator(final T element) {
4713 return new Spliterator<T>() {
4714 long est = 1;
4715
4716 @Override
4717 public Spliterator<T> trySplit() {
4718 return null;
4719 }
4720
4721 @Override
4722 public boolean tryAdvance(Consumer<? super T> consumer) {
4723 Objects.requireNonNull(consumer);
4724 if (est > 0) {
4725 est--;
4726 consumer.accept(element);
4727 return true;
4728 }
4729 return false;
4730 }
4731
4732 @Override
4733 public void forEachRemaining(Consumer<? super T> consumer) {
4734 tryAdvance(consumer);
4735 }
4736
4737 @Override
4738 public long estimateSize() {
4739 return est;
4740 }
4741
4742 @Override
4743 public int characteristics() {
4744 int value = (element != null) ? Spliterator.NONNULL : 0;
4745
4746 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE |
4747 Spliterator.DISTINCT | Spliterator.ORDERED;
4748 }
4749 };
4750 }
4751
4752 /**
4753 * @serial include
4754 */
4755 private static class SingletonSet<E>
4756 extends AbstractSet<E>
4757 implements Serializable
4758 {
4759 private static final long serialVersionUID = 3193687207550431679L;
4760
4761 private final E element;
4762
4763 SingletonSet(E e) {element = e;}
4764
4765 public Iterator<E> iterator() {
4766 return singletonIterator(element);
4767 }
4768
4769 public int size() {return 1;}
4770
4771 public boolean contains(Object o) {return eq(o, element);}
4772
4773 // Override default methods for Collection
4774 @Override
4775 public void forEach(Consumer<? super E> action) {
4776 action.accept(element);
4777 }
4778 @Override
4779 public Spliterator<E> spliterator() {
4780 return singletonSpliterator(element);
4781 }
4782 @Override
4783 public boolean removeIf(Predicate<? super E> filter) {
4784 throw new UnsupportedOperationException();
4785 }
4786 @Override
4787 public int hashCode() {
4788 return Objects.hashCode(element);
4789 }
4790 }
4791
4792 /**
4793 * Returns an immutable list containing only the specified object.
4794 * The returned list is serializable.
4795 *
4796 * @param <T> the class of the objects in the list
4797 * @param o the sole object to be stored in the returned list.
4798 * @return an immutable list containing only the specified object.
4799 * @since 1.3
4800 */
4801 public static <T> List<T> singletonList(T o) {
4802 return new SingletonList<>(o);
4803 }
4804
4805 /**
4806 * @serial include
4807 */
4808 private static class SingletonList<E>
4809 extends AbstractList<E>
4810 implements RandomAccess, Serializable {
4811
4812 private static final long serialVersionUID = 3093736618740652951L;
4813
4814 private final E element;
4815
4816 SingletonList(E obj) {element = obj;}
4817
4818 public Iterator<E> iterator() {
4819 return singletonIterator(element);
4820 }
4821
4822 public int size() {return 1;}
4823
4824 public boolean contains(Object obj) {return eq(obj, element);}
4825
4826 public E get(int index) {
4827 if (index != 0)
4828 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1");
4829 return element;
4830 }
4831
4832 // Override default methods for Collection
4833 @Override
4834 public void forEach(Consumer<? super E> action) {
4835 action.accept(element);
4836 }
4837 @Override
4838 public boolean removeIf(Predicate<? super E> filter) {
4839 throw new UnsupportedOperationException();
4840 }
4841 @Override
4842 public void replaceAll(UnaryOperator<E> operator) {
4843 throw new UnsupportedOperationException();
4844 }
4845 @Override
4846 public void sort(Comparator<? super E> c) {
4847 }
4848 @Override
4849 public Spliterator<E> spliterator() {
4850 return singletonSpliterator(element);
4851 }
4852 @Override
4853 public int hashCode() {
4854 return 31 + Objects.hashCode(element);
4855 }
4856 }
4857
4858 /**
4859 * Returns an immutable map, mapping only the specified key to the
4860 * specified value. The returned map is serializable.
4861 *
4862 * @param <K> the class of the map keys
4863 * @param <V> the class of the map values
4864 * @param key the sole key to be stored in the returned map.
4865 * @param value the value to which the returned map maps {@code key}.
4866 * @return an immutable map containing only the specified key-value
4867 * mapping.
4868 * @since 1.3
4869 */
4870 public static <K,V> Map<K,V> singletonMap(K key, V value) {
4871 return new SingletonMap<>(key, value);
4872 }
4873
4874 /**
4875 * @serial include
4876 */
4877 private static class SingletonMap<K,V>
4878 extends AbstractMap<K,V>
4879 implements Serializable {
4880 private static final long serialVersionUID = -6979724477215052911L;
4881
4882 private final K k;
4883 private final V v;
4884
4885 SingletonMap(K key, V value) {
4886 k = key;
4887 v = value;
4888 }
4889
4890 public int size() {return 1;}
4891 public boolean isEmpty() {return false;}
4892 public boolean containsKey(Object key) {return eq(key, k);}
4893 public boolean containsValue(Object value) {return eq(value, v);}
4894 public V get(Object key) {return (eq(key, k) ? v : null);}
4895
4896 private transient Set<K> keySet;
4897 private transient Set<Map.Entry<K,V>> entrySet;
4898 private transient Collection<V> values;
4899
4900 public Set<K> keySet() {
4901 if (keySet==null)
4902 keySet = singleton(k);
4903 return keySet;
4904 }
4905
4906 public Set<Map.Entry<K,V>> entrySet() {
4907 if (entrySet==null)
4908 entrySet = Collections.<Map.Entry<K,V>>singleton(
4909 new SimpleImmutableEntry<>(k, v));
4910 return entrySet;
4911 }
4912
4913 public Collection<V> values() {
4914 if (values==null)
4915 values = singleton(v);
4916 return values;
4917 }
4918
4919 // Override default methods in Map
4920 @Override
4921 public V getOrDefault(Object key, V defaultValue) {
4922 return eq(key, k) ? v : defaultValue;
4923 }
4924
4925 @Override
4926 public void forEach(BiConsumer<? super K, ? super V> action) {
4927 action.accept(k, v);
4928 }
4929
4930 @Override
4931 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
4932 throw new UnsupportedOperationException();
4933 }
4934
4935 @Override
4936 public V putIfAbsent(K key, V value) {
4937 throw new UnsupportedOperationException();
4938 }
4939
4940 @Override
4941 public boolean remove(Object key, Object value) {
4942 throw new UnsupportedOperationException();
4943 }
4944
4945 @Override
4946 public boolean replace(K key, V oldValue, V newValue) {
4947 throw new UnsupportedOperationException();
4948 }
4949
4950 @Override
4951 public V replace(K key, V value) {
4952 throw new UnsupportedOperationException();
4953 }
4954
4955 @Override
4956 public V computeIfAbsent(K key,
4957 Function<? super K, ? extends V> mappingFunction) {
4958 throw new UnsupportedOperationException();
4959 }
4960
4961 @Override
4962 public V computeIfPresent(K key,
4963 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4964 throw new UnsupportedOperationException();
4965 }
4966
4967 @Override
4968 public V compute(K key,
4969 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
4970 throw new UnsupportedOperationException();
4971 }
4972
4973 @Override
4974 public V merge(K key, V value,
4975 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
4976 throw new UnsupportedOperationException();
4977 }
4978
4979 @Override
4980 public int hashCode() {
4981 return Objects.hashCode(k) ^ Objects.hashCode(v);
4982 }
4983 }
4984
4985 // Miscellaneous
4986
4987 /**
4988 * Returns an immutable list consisting of {@code n} copies of the
4989 * specified object. The newly allocated data object is tiny (it contains
4990 * a single reference to the data object). This method is useful in
4991 * combination with the {@code List.addAll} method to grow lists.
4992 * The returned list is serializable.
4993 *
4994 * @param <T> the class of the object to copy and of the objects
4995 * in the returned list.
4996 * @param n the number of elements in the returned list.
4997 * @param o the element to appear repeatedly in the returned list.
4998 * @return an immutable list consisting of {@code n} copies of the
4999 * specified object.
5000 * @throws IllegalArgumentException if {@code n < 0}
5001 * @see List#addAll(Collection)
5002 * @see List#addAll(int, Collection)
5003 */
5004 public static <T> List<T> nCopies(int n, T o) {
5005 if (n < 0)
5006 throw new IllegalArgumentException("List length = " + n);
5007 return new CopiesList<>(n, o);
5008 }
5009
5010 /**
5011 * @serial include
5012 */
5013 private static class CopiesList<E>
5014 extends AbstractList<E>
5015 implements RandomAccess, Serializable
5016 {
5017 private static final long serialVersionUID = 2739099268398711800L;
5018
5019 final int n;
5020 final E element;
5021
5022 CopiesList(int n, E e) {
5023 assert n >= 0;
5024 this.n = n;
5025 element = e;
5026 }
5027
5028 public int size() {
5029 return n;
5030 }
5031
5032 public boolean contains(Object obj) {
5033 return n != 0 && eq(obj, element);
5034 }
5035
5036 public int indexOf(Object o) {
5037 return contains(o) ? 0 : -1;
5038 }
5039
5040 public int lastIndexOf(Object o) {
5041 return contains(o) ? n - 1 : -1;
5042 }
5043
5044 public E get(int index) {
5045 if (index < 0 || index >= n)
5046 throw new IndexOutOfBoundsException("Index: "+index+
5047 ", Size: "+n);
5048 return element;
5049 }
5050
5051 public Object[] toArray() {
5052 final Object[] a = new Object[n];
5053 if (element != null)
5054 Arrays.fill(a, 0, n, element);
5055 return a;
5056 }
5057
5058 @SuppressWarnings("unchecked")
5059 public <T> T[] toArray(T[] a) {
5060 final int n = this.n;
5061 if (a.length < n) {
5062 a = (T[])java.lang.reflect.Array
5063 .newInstance(a.getClass().getComponentType(), n);
5064 if (element != null)
5065 Arrays.fill(a, 0, n, element);
5066 } else {
5067 Arrays.fill(a, 0, n, element);
5068 if (a.length > n)
5069 a[n] = null;
5070 }
5071 return a;
5072 }
5073
5074 public List<E> subList(int fromIndex, int toIndex) {
5075 if (fromIndex < 0)
5076 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
5077 if (toIndex > n)
5078 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
5079 if (fromIndex > toIndex)
5080 throw new IllegalArgumentException("fromIndex(" + fromIndex +
5081 ") > toIndex(" + toIndex + ")");
5082 return new CopiesList<>(toIndex - fromIndex, element);
5083 }
5084
5085 // Override default methods in Collection
5086 @Override
5087 public Stream<E> stream() {
5088 return IntStream.range(0, n).mapToObj(i -> element);
5089 }
5090
5091 @Override
5092 public Stream<E> parallelStream() {
5093 return IntStream.range(0, n).parallel().mapToObj(i -> element);
5094 }
5095
5096 @Override
5097 public Spliterator<E> spliterator() {
5098 return stream().spliterator();
5099 }
5100 }
5101
5102 /**
5103 * Returns a comparator that imposes the reverse of the <em>natural
5104 * ordering</em> on a collection of objects that implement the
5105 * {@code Comparable} interface. (The natural ordering is the ordering
5106 * imposed by the objects' own {@code compareTo} method.) This enables a
5107 * simple idiom for sorting (or maintaining) collections (or arrays) of
5108 * objects that implement the {@code Comparable} interface in
5109 * reverse-natural-order. For example, suppose {@code a} is an array of
5110 * strings. Then: <pre>
5111 * Arrays.sort(a, Collections.reverseOrder());
5112 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p>
5113 *
5114 * The returned comparator is serializable.
5115 *
5116 * @param <T> the class of the objects compared by the comparator
5117 * @return A comparator that imposes the reverse of the <i>natural
5118 * ordering</i> on a collection of objects that implement
5119 * the {@code Comparable} interface.
5120 * @see Comparable
5121 */
5122 @SuppressWarnings("unchecked")
5123 public static <T> Comparator<T> reverseOrder() {
5124 return (Comparator<T>) ReverseComparator.REVERSE_ORDER;
5125 }
5126
5127 /**
5128 * @serial include
5129 */
5130 private static class ReverseComparator
5131 implements Comparator<Comparable<Object>>, Serializable {
5132
5133 private static final long serialVersionUID = 7207038068494060240L;
5134
5135 static final ReverseComparator REVERSE_ORDER
5136 = new ReverseComparator();
5137
5138 public int compare(Comparable<Object> c1, Comparable<Object> c2) {
5139 return c2.compareTo(c1);
5140 }
5141
5142 private Object readResolve() { return Collections.reverseOrder(); }
5143
5144 @Override
5145 public Comparator<Comparable<Object>> reversed() {
5146 return Comparator.naturalOrder();
5147 }
5148 }
5149
5150 /**
5151 * Returns a comparator that imposes the reverse ordering of the specified
5152 * comparator. If the specified comparator is {@code null}, this method is
5153 * equivalent to {@link #reverseOrder()} (in other words, it returns a
5154 * comparator that imposes the reverse of the <em>natural ordering</em> on
5155 * a collection of objects that implement the Comparable interface).
5156 *
5157 * <p>The returned comparator is serializable (assuming the specified
5158 * comparator is also serializable or {@code null}).
5159 *
5160 * @param <T> the class of the objects compared by the comparator
5161 * @param cmp a comparator who's ordering is to be reversed by the returned
5162 * comparator or {@code null}
5163 * @return A comparator that imposes the reverse ordering of the
5164 * specified comparator.
5165 * @since 1.5
5166 */
5167 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) {
5168 if (cmp == null)
5169 return reverseOrder();
5170
5171 if (cmp instanceof ReverseComparator2)
5172 return ((ReverseComparator2<T>)cmp).cmp;
5173
5174 return new ReverseComparator2<>(cmp);
5175 }
5176
5177 /**
5178 * @serial include
5179 */
5180 private static class ReverseComparator2<T> implements Comparator<T>,
5181 Serializable
5182 {
5183 private static final long serialVersionUID = 4374092139857L;
5184
5185 /**
5186 * The comparator specified in the static factory. This will never
5187 * be null, as the static factory returns a ReverseComparator
5188 * instance if its argument is null.
5189 *
5190 * @serial
5191 */
5192 final Comparator<T> cmp;
5193
5194 ReverseComparator2(Comparator<T> cmp) {
5195 assert cmp != null;
5196 this.cmp = cmp;
5197 }
5198
5199 public int compare(T t1, T t2) {
5200 return cmp.compare(t2, t1);
5201 }
5202
5203 public boolean equals(Object o) {
5204 return (o == this) ||
5205 (o instanceof ReverseComparator2 &&
5206 cmp.equals(((ReverseComparator2)o).cmp));
5207 }
5208
5209 public int hashCode() {
5210 return cmp.hashCode() ^ Integer.MIN_VALUE;
5211 }
5212
5213 @Override
5214 public Comparator<T> reversed() {
5215 return cmp;
5216 }
5217 }
5218
5219 /**
5220 * Returns an enumeration over the specified collection. This provides
5221 * interoperability with legacy APIs that require an enumeration
5222 * as input.
5223 *
5224 * <p>The iterator returned from a call to {@link Enumeration#asIterator()}
5225 * does not support removal of elements from the specified collection. This
5226 * is necessary to avoid unintentionally increasing the capabilities of the
5227 * returned enumeration.
5228 *
5229 * @param <T> the class of the objects in the collection
5230 * @param c the collection for which an enumeration is to be returned.
5231 * @return an enumeration over the specified collection.
5232 * @see Enumeration
5233 */
5234 public static <T> Enumeration<T> enumeration(final Collection<T> c) {
5235 return new Enumeration<T>() {
5236 private final Iterator<T> i = c.iterator();
5237
5238 public boolean hasMoreElements() {
5239 return i.hasNext();
5240 }
5241
5242 public T nextElement() {
5243 return i.next();
5244 }
5245 };
5246 }
5247
5248 /**
5249 * Returns an array list containing the elements returned by the
5250 * specified enumeration in the order they are returned by the
5251 * enumeration. This method provides interoperability between
5252 * legacy APIs that return enumerations and new APIs that require
5253 * collections.
5254 *
5255 * @param <T> the class of the objects returned by the enumeration
5256 * @param e enumeration providing elements for the returned
5257 * array list
5258 * @return an array list containing the elements returned
5259 * by the specified enumeration.
5260 * @since 1.4
5261 * @see Enumeration
5262 * @see ArrayList
5263 */
5264 public static <T> ArrayList<T> list(Enumeration<T> e) {
5265 ArrayList<T> l = new ArrayList<>();
5266 while (e.hasMoreElements())
5267 l.add(e.nextElement());
5268 return l;
5269 }
5270
5271 /**
5272 * Returns true if the specified arguments are equal, or both null.
5273 *
5274 * NB: Do not replace with Object.equals until JDK-8015417 is resolved.
5275 */
5276 static boolean eq(Object o1, Object o2) {
5277 return o1==null ? o2==null : o1.equals(o2);
5278 }
5279
5280 /**
5281 * Returns the number of elements in the specified collection equal to the
5282 * specified object. More formally, returns the number of elements
5283 * {@code e} in the collection such that
5284 * {@code Objects.equals(o, e)}.
5285 *
5286 * @param c the collection in which to determine the frequency
5287 * of {@code o}
5288 * @param o the object whose frequency is to be determined
5289 * @return the number of elements in {@code c} equal to {@code o}
5290 * @throws NullPointerException if {@code c} is null
5291 * @since 1.5
5292 */
5293 public static int frequency(Collection<?> c, Object o) {
5294 int result = 0;
5295 if (o == null) {
5296 for (Object e : c)
5297 if (e == null)
5298 result++;
5299 } else {
5300 for (Object e : c)
5301 if (o.equals(e))
5302 result++;
5303 }
5304 return result;
5305 }
5306
5307 /**
5308 * Returns {@code true} if the two specified collections have no
5309 * elements in common.
5310 *
5311 * <p>Care must be exercised if this method is used on collections that
5312 * do not comply with the general contract for {@code Collection}.
5313 * Implementations may elect to iterate over either collection and test
5314 * for containment in the other collection (or to perform any equivalent
5315 * computation). If either collection uses a nonstandard equality test
5316 * (as does a {@link SortedSet} whose ordering is not <em>compatible with
5317 * equals</em>, or the key set of an {@link IdentityHashMap}), both
5318 * collections must use the same nonstandard equality test, or the
5319 * result of this method is undefined.
5320 *
5321 * <p>Care must also be exercised when using collections that have
5322 * restrictions on the elements that they may contain. Collection
5323 * implementations are allowed to throw exceptions for any operation
5324 * involving elements they deem ineligible. For absolute safety the
5325 * specified collections should contain only elements which are
5326 * eligible elements for both collections.
5327 *
5328 * <p>Note that it is permissible to pass the same collection in both
5329 * parameters, in which case the method will return {@code true} if and
5330 * only if the collection is empty.
5331 *
5332 * @param c1 a collection
5333 * @param c2 a collection
5334 * @return {@code true} if the two specified collections have no
5335 * elements in common.
5336 * @throws NullPointerException if either collection is {@code null}.
5337 * @throws NullPointerException if one collection contains a {@code null}
5338 * element and {@code null} is not an eligible element for the other collection.
5339 * (<a href="Collection.html#optional-restrictions">optional</a>)
5340 * @throws ClassCastException if one collection contains an element that is
5341 * of a type which is ineligible for the other collection.
5342 * (<a href="Collection.html#optional-restrictions">optional</a>)
5343 * @since 1.5
5344 */
5345 public static boolean disjoint(Collection<?> c1, Collection<?> c2) {
5346 // The collection to be used for contains(). Preference is given to
5347 // the collection who's contains() has lower O() complexity.
5348 Collection<?> contains = c2;
5349 // The collection to be iterated. If the collections' contains() impl
5350 // are of different O() complexity, the collection with slower
5351 // contains() will be used for iteration. For collections who's
5352 // contains() are of the same complexity then best performance is
5353 // achieved by iterating the smaller collection.
5354 Collection<?> iterate = c1;
5355
5356 // Performance optimization cases. The heuristics:
5357 // 1. Generally iterate over c1.
5358 // 2. If c1 is a Set then iterate over c2.
5359 // 3. If either collection is empty then result is always true.
5360 // 4. Iterate over the smaller Collection.
5361 if (c1 instanceof Set) {
5362 // Use c1 for contains as a Set's contains() is expected to perform
5363 // better than O(N/2)
5364 iterate = c2;
5365 contains = c1;
5366 } else if (!(c2 instanceof Set)) {
5367 // Both are mere Collections. Iterate over smaller collection.
5368 // Example: If c1 contains 3 elements and c2 contains 50 elements and
5369 // assuming contains() requires ceiling(N/2) comparisons then
5370 // checking for all c1 elements in c2 would require 75 comparisons
5371 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring
5372 // 100 comparisons (50 * ceiling(3/2)).
5373 int c1size = c1.size();
5374 int c2size = c2.size();
5375 if (c1size == 0 || c2size == 0) {
5376 // At least one collection is empty. Nothing will match.
5377 return true;
5378 }
5379
5380 if (c1size > c2size) {
5381 iterate = c2;
5382 contains = c1;
5383 }
5384 }
5385
5386 for (Object e : iterate) {
5387 if (contains.contains(e)) {
5388 // Found a common element. Collections are not disjoint.
5389 return false;
5390 }
5391 }
5392
5393 // No common elements were found.
5394 return true;
5395 }
5396
5397 /**
5398 * Adds all of the specified elements to the specified collection.
5399 * Elements to be added may be specified individually or as an array.
5400 * The behavior of this convenience method is identical to that of
5401 * {@code c.addAll(Arrays.asList(elements))}.
5402 *
5403 * <p>When elements are specified individually, this method provides a
5404 * convenient way to add a few elements to an existing collection:
5405 * <pre>
5406 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon");
5407 * </pre>
5408 *
5409 * @param <T> the class of the elements to add and of the collection
5410 * @param c the collection into which {@code elements} are to be inserted
5411 * @param elements the elements to insert into {@code c}
5412 * @return {@code true} if the collection changed as a result of the call
5413 * @throws UnsupportedOperationException if {@code c} does not support
5414 * the {@code add} operation
5415 * @throws NullPointerException if {@code elements} contains one or more
5416 * null values and {@code c} does not permit null elements, or
5417 * if {@code c} or {@code elements} are {@code null}
5418 * @throws IllegalArgumentException if some property of a value in
5419 * {@code elements} prevents it from being added to {@code c}
5420 * @see Collection#addAll(Collection)
5421 * @since 1.5
5422 */
5423 @SafeVarargs
5424 @SuppressWarnings("varargs")
5425 public static <T> boolean addAll(Collection<? super T> c, T... elements) {
5426 return c.addAll(Arrays.asList(elements));
5427 }
5428
5429 /**
5430 * Returns a set backed by the specified map. The resulting set displays
5431 * the same ordering, concurrency, and performance characteristics as the
5432 * backing map. In essence, this factory method provides a {@link Set}
5433 * implementation corresponding to any {@link Map} implementation. There
5434 * is no need to use this method on a {@link Map} implementation that
5435 * already has a corresponding {@link Set} implementation (such as {@link
5436 * HashMap} or {@link TreeMap}).
5437 *
5438 * <p>Each method invocation on the set returned by this method results in
5439 * exactly one method invocation on the backing map or its {@code keySet}
5440 * view, with one exception. The {@code addAll} method is implemented
5441 * as a sequence of {@code put} invocations on the backing map.
5442 *
5443 * <p>The specified map must be empty at the time this method is invoked,
5444 * and should not be accessed directly after this method returns. These
5445 * conditions are ensured if the map is created empty, passed directly
5446 * to this method, and no reference to the map is retained, as illustrated
5447 * in the following code fragment:
5448 * <pre>
5449 * Set<Object> weakHashSet = Collections.newSetFromMap(
5450 * new WeakHashMap<Object, Boolean>());
5451 * </pre>
5452 *
5453 * @param <E> the class of the map keys and of the objects in the
5454 * returned set
5455 * @param map the backing map
5456 * @return the set backed by the map
5457 * @throws IllegalArgumentException if {@code map} is not empty
5458 * @since 1.6
5459 */
5460 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
5461 return new SetFromMap<>(map);
5462 }
5463
5464 /**
5465 * @serial include
5466 */
5467 private static class SetFromMap<E> extends AbstractSet<E>
5468 implements Set<E>, Serializable
5469 {
5470 private final Map<E, Boolean> m; // The backing map
5471 private transient Set<E> s; // Its keySet
5472
5473 SetFromMap(Map<E, Boolean> map) {
5474 if (!map.isEmpty())
5475 throw new IllegalArgumentException("Map is non-empty");
5476 m = map;
5477 s = map.keySet();
5478 }
5479
5480 public void clear() { m.clear(); }
5481 public int size() { return m.size(); }
5482 public boolean isEmpty() { return m.isEmpty(); }
5483 public boolean contains(Object o) { return m.containsKey(o); }
5484 public boolean remove(Object o) { return m.remove(o) != null; }
5485 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
5486 public Iterator<E> iterator() { return s.iterator(); }
5487 public Object[] toArray() { return s.toArray(); }
5488 public <T> T[] toArray(T[] a) { return s.toArray(a); }
5489 public String toString() { return s.toString(); }
5490 public int hashCode() { return s.hashCode(); }
5491 public boolean equals(Object o) { return o == this || s.equals(o); }
5492 public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
5493 public boolean removeAll(Collection<?> c) {return s.removeAll(c);}
5494 public boolean retainAll(Collection<?> c) {return s.retainAll(c);}
5495 // addAll is the only inherited implementation
5496
5497 // Override default methods in Collection
5498 @Override
5499 public void forEach(Consumer<? super E> action) {
5500 s.forEach(action);
5501 }
5502 @Override
5503 public boolean removeIf(Predicate<? super E> filter) {
5504 return s.removeIf(filter);
5505 }
5506
5507 @Override
5508 public Spliterator<E> spliterator() {return s.spliterator();}
5509 @Override
5510 public Stream<E> stream() {return s.stream();}
5511 @Override
5512 public Stream<E> parallelStream() {return s.parallelStream();}
5513
5514 private static final long serialVersionUID = 2454657854757543876L;
5515
5516 private void readObject(java.io.ObjectInputStream stream)
5517 throws IOException, ClassNotFoundException
5518 {
5519 stream.defaultReadObject();
5520 s = m.keySet();
5521 }
5522 }
5523
5524 /**
5525 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo)
5526 * {@link Queue}. Method {@code add} is mapped to {@code push},
5527 * {@code remove} is mapped to {@code pop} and so on. This
5528 * view can be useful when you would like to use a method
5529 * requiring a {@code Queue} but you need Lifo ordering.
5530 *
5531 * <p>Each method invocation on the queue returned by this method
5532 * results in exactly one method invocation on the backing deque, with
5533 * one exception. The {@link Queue#addAll addAll} method is
5534 * implemented as a sequence of {@link Deque#addFirst addFirst}
5535 * invocations on the backing deque.
5536 *
5537 * @param <T> the class of the objects in the deque
5538 * @param deque the deque
5539 * @return the queue
5540 * @since 1.6
5541 */
5542 public static <T> Queue<T> asLifoQueue(Deque<T> deque) {
5543 return new AsLIFOQueue<>(Objects.requireNonNull(deque));
5544 }
5545
5546 /**
5547 * @serial include
5548 */
5549 static class AsLIFOQueue<E> extends AbstractQueue<E>
5550 implements Queue<E>, Serializable {
5551 private static final long serialVersionUID = 1802017725587941708L;
5552 private final Deque<E> q;
5553 AsLIFOQueue(Deque<E> q) { this.q = q; }
5554 public boolean add(E e) { q.addFirst(e); return true; }
5555 public boolean offer(E e) { return q.offerFirst(e); }
5556 public E poll() { return q.pollFirst(); }
5557 public E remove() { return q.removeFirst(); }
5558 public E peek() { return q.peekFirst(); }
5559 public E element() { return q.getFirst(); }
5560 public void clear() { q.clear(); }
5561 public int size() { return q.size(); }
5562 public boolean isEmpty() { return q.isEmpty(); }
5563 public boolean contains(Object o) { return q.contains(o); }
5564 public boolean remove(Object o) { return q.remove(o); }
5565 public Iterator<E> iterator() { return q.iterator(); }
5566 public Object[] toArray() { return q.toArray(); }
5567 public <T> T[] toArray(T[] a) { return q.toArray(a); }
5568 public String toString() { return q.toString(); }
5569 public boolean containsAll(Collection<?> c) {return q.containsAll(c);}
5570 public boolean removeAll(Collection<?> c) {return q.removeAll(c);}
5571 public boolean retainAll(Collection<?> c) {return q.retainAll(c);}
5572 // We use inherited addAll; forwarding addAll would be wrong
5573
5574 // Override default methods in Collection
5575 @Override
5576 public void forEach(Consumer<? super E> action) {q.forEach(action);}
5577 @Override
5578 public boolean removeIf(Predicate<? super E> filter) {
5579 return q.removeIf(filter);
5580 }
5581 @Override
5582 public Spliterator<E> spliterator() {return q.spliterator();}
5583 @Override
5584 public Stream<E> stream() {return q.stream();}
5585 @Override
5586 public Stream<E> parallelStream() {return q.parallelStream();}
5587 }
5588 }