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