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 @SuppressWarnings("unchecked") 3035 E typeCheck(Object o) { 3036 if (o != null && !type.isInstance(o)) 3037 throw new ClassCastException(badElementMsg(o)); 3038 return (E) o; 3039 } 3040 3041 private String badElementMsg(Object o) { 3042 return "Attempt to insert " + o.getClass() + 3043 " element into collection with element type " + type; 3044 } 3045 3046 CheckedCollection(Collection<E> c, Class<E> type) { 3047 this.c = Objects.requireNonNull(c, "c"); 3048 this.type = Objects.requireNonNull(type, "type"); 3049 } 3050 3051 public int size() { return c.size(); } 3052 public boolean isEmpty() { return c.isEmpty(); } 3053 public boolean contains(Object o) { return c.contains(o); } 3054 public Object[] toArray() { return c.toArray(); } 3055 public <T> T[] toArray(T[] a) { return c.toArray(a); } 3056 public String toString() { return c.toString(); } 3057 public boolean remove(Object o) { return c.remove(o); } 3058 public void clear() { c.clear(); } 3059 3060 public boolean containsAll(Collection<?> coll) { 3061 return c.containsAll(coll); 3062 } 3063 public boolean removeAll(Collection<?> coll) { 3064 return c.removeAll(coll); 3065 } 3066 public boolean retainAll(Collection<?> coll) { 3067 return c.retainAll(coll); 3068 } 3069 3070 public Iterator<E> iterator() { 3071 // JDK-6363904 - unwrapped iterator could be typecast to 3072 // ListIterator with unsafe set() 3073 final Iterator<E> it = c.iterator(); 3074 return new Iterator<E>() { 3075 public boolean hasNext() { return it.hasNext(); } 3076 public E next() { return it.next(); } 3077 public void remove() { it.remove(); }}; 3078 } 3079 3080 public boolean add(E e) { 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; 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 /** 3491 * {@inheritDoc} 3492 * 3493 * @throws ClassCastException if the class of an element returned by the 3494 * operator prevents it from being added to this collection. The 3495 * exception may be thrown after some elements of the list have 3496 * already been replaced. 3497 */ 3498 @Override 3499 public void replaceAll(UnaryOperator<E> operator) { 3500 list.replaceAll(e -> typeCheck(operator.apply(e))); 3501 } 3502 3503 @Override 3504 public void sort(Comparator<? super E> c) { 3505 list.sort(c); 3506 } 3507 } 3508 3509 /** 3510 * @serial include 3511 */ 3512 static class CheckedRandomAccessList<E> extends CheckedList<E> 3513 implements RandomAccess 3514 { 3515 private static final long serialVersionUID = 1638200125423088369L; 3516 3517 CheckedRandomAccessList(List<E> list, Class<E> type) { 3518 super(list, type); 3519 } 3520 3521 public List<E> subList(int fromIndex, int toIndex) { 3522 return new CheckedRandomAccessList<>( 3523 list.subList(fromIndex, toIndex), type); 3524 } 3525 } 3526 3527 /** 3528 * Returns a dynamically typesafe view of the specified map. 3529 * Any attempt to insert a mapping whose key or value have the wrong 3530 * type will result in an immediate {@link ClassCastException}. 3531 * Similarly, any attempt to modify the value currently associated with 3532 * a key will result in an immediate {@link ClassCastException}, 3533 * whether the modification is attempted directly through the map 3534 * itself, or through a {@link Map.Entry} instance obtained from the 3535 * map's {@link Map#entrySet() entry set} view. 3536 * 3537 * <p>Assuming a map contains no incorrectly typed keys or values 3538 * prior to the time a dynamically typesafe view is generated, and 3539 * that all subsequent access to the map takes place through the view 3540 * (or one of its collection views), it is <i>guaranteed</i> that the 3541 * map cannot contain an incorrectly typed key or value. 3542 * 3543 * <p>A discussion of the use of dynamically typesafe views may be 3544 * found in the documentation for the {@link #checkedCollection 3545 * checkedCollection} method. 3546 * 3547 * <p>The returned map will be serializable if the specified map is 3548 * serializable. 3549 * 3550 * <p>Since {@code null} is considered to be a value of any reference 3551 * type, the returned map permits insertion of null keys or values 3552 * whenever the backing map does. 3553 * 3554 * @param <K> the class of the map keys 3555 * @param <V> the class of the map values 3556 * @param m the map for which a dynamically typesafe view is to be 3557 * returned 3558 * @param keyType the type of key that {@code m} is permitted to hold 3559 * @param valueType the type of value that {@code m} is permitted to hold 3560 * @return a dynamically typesafe view of the specified map 3561 * @since 1.5 3562 */ 3563 public static <K, V> Map<K, V> checkedMap(Map<K, V> m, 3564 Class<K> keyType, 3565 Class<V> valueType) { 3566 return new CheckedMap<>(m, keyType, valueType); 3567 } 3568 3569 3570 /** 3571 * @serial include 3572 */ 3573 private static class CheckedMap<K,V> 3574 implements Map<K,V>, Serializable 3575 { 3576 private static final long serialVersionUID = 5742860141034234728L; 3577 3578 private final Map<K, V> m; 3579 final Class<K> keyType; 3580 final Class<V> valueType; 3581 3582 private void typeCheck(Object key, Object value) { 3583 if (key != null && !keyType.isInstance(key)) 3584 throw new ClassCastException(badKeyMsg(key)); 3585 3586 if (value != null && !valueType.isInstance(value)) 3587 throw new ClassCastException(badValueMsg(value)); 3588 } 3589 3590 private BiFunction<? super K, ? super V, ? extends V> typeCheck( 3591 BiFunction<? super K, ? super V, ? extends V> func) { 3592 Objects.requireNonNull(func); 3593 return (k, v) -> { 3594 V newValue = func.apply(k, v); 3595 typeCheck(k, newValue); 3596 return newValue; 3597 }; 3598 } 3599 3600 private String badKeyMsg(Object key) { 3601 return "Attempt to insert " + key.getClass() + 3602 " key into map with key type " + keyType; 3603 } 3604 3605 private String badValueMsg(Object value) { 3606 return "Attempt to insert " + value.getClass() + 3607 " value into map with value type " + valueType; 3608 } 3609 3610 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) { 3611 this.m = Objects.requireNonNull(m); 3612 this.keyType = Objects.requireNonNull(keyType); 3613 this.valueType = Objects.requireNonNull(valueType); 3614 } 3615 3616 public int size() { return m.size(); } 3617 public boolean isEmpty() { return m.isEmpty(); } 3618 public boolean containsKey(Object key) { return m.containsKey(key); } 3619 public boolean containsValue(Object v) { return m.containsValue(v); } 3620 public V get(Object key) { return m.get(key); } 3621 public V remove(Object key) { return m.remove(key); } 3622 public void clear() { m.clear(); } 3623 public Set<K> keySet() { return m.keySet(); } 3624 public Collection<V> values() { return m.values(); } 3625 public boolean equals(Object o) { return o == this || m.equals(o); } 3626 public int hashCode() { return m.hashCode(); } 3627 public String toString() { return m.toString(); } 3628 3629 public V put(K key, V value) { 3630 typeCheck(key, value); 3631 return m.put(key, value); 3632 } 3633 3634 @SuppressWarnings("unchecked") 3635 public void putAll(Map<? extends K, ? extends V> t) { 3636 // Satisfy the following goals: 3637 // - good diagnostics in case of type mismatch 3638 // - all-or-nothing semantics 3639 // - protection from malicious t 3640 // - correct behavior if t is a concurrent map 3641 Object[] entries = t.entrySet().toArray(); 3642 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length); 3643 for (Object o : entries) { 3644 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 3645 Object k = e.getKey(); 3646 Object v = e.getValue(); 3647 typeCheck(k, v); 3648 checked.add( 3649 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v)); 3650 } 3651 for (Map.Entry<K,V> e : checked) 3652 m.put(e.getKey(), e.getValue()); 3653 } 3654 3655 private transient Set<Map.Entry<K,V>> entrySet; 3656 3657 public Set<Map.Entry<K,V>> entrySet() { 3658 if (entrySet==null) 3659 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType); 3660 return entrySet; 3661 } 3662 3663 // Override default methods in Map 3664 @Override 3665 public void forEach(BiConsumer<? super K, ? super V> action) { 3666 m.forEach(action); 3667 } 3668 3669 @Override 3670 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 3671 m.replaceAll(typeCheck(function)); 3672 } 3673 3674 @Override 3675 public V putIfAbsent(K key, V value) { 3676 typeCheck(key, value); 3677 return m.putIfAbsent(key, value); 3678 } 3679 3680 @Override 3681 public boolean remove(Object key, Object value) { 3682 return m.remove(key, value); 3683 } 3684 3685 @Override 3686 public boolean replace(K key, V oldValue, V newValue) { 3687 typeCheck(key, newValue); 3688 return m.replace(key, oldValue, newValue); 3689 } 3690 3691 @Override 3692 public V replace(K key, V value) { 3693 typeCheck(key, value); 3694 return m.replace(key, value); 3695 } 3696 3697 @Override 3698 public V computeIfAbsent(K key, 3699 Function<? super K, ? extends V> mappingFunction) { 3700 Objects.requireNonNull(mappingFunction); 3701 return m.computeIfAbsent(key, k -> { 3702 V value = mappingFunction.apply(k); 3703 typeCheck(k, value); 3704 return value; 3705 }); 3706 } 3707 3708 @Override 3709 public V computeIfPresent(K key, 3710 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 3711 return m.computeIfPresent(key, typeCheck(remappingFunction)); 3712 } 3713 3714 @Override 3715 public V compute(K key, 3716 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 3717 return m.compute(key, typeCheck(remappingFunction)); 3718 } 3719 3720 @Override 3721 public V merge(K key, V value, 3722 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 3723 Objects.requireNonNull(remappingFunction); 3724 return m.merge(key, value, (v1, v2) -> { 3725 V newValue = remappingFunction.apply(v1, v2); 3726 typeCheck(null, newValue); 3727 return newValue; 3728 }); 3729 } 3730 3731 /** 3732 * We need this class in addition to CheckedSet as Map.Entry permits 3733 * modification of the backing Map via the setValue operation. This 3734 * class is subtle: there are many possible attacks that must be 3735 * thwarted. 3736 * 3737 * @serial exclude 3738 */ 3739 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> { 3740 private final Set<Map.Entry<K,V>> s; 3741 private final Class<V> valueType; 3742 3743 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) { 3744 this.s = s; 3745 this.valueType = valueType; 3746 } 3747 3748 public int size() { return s.size(); } 3749 public boolean isEmpty() { return s.isEmpty(); } 3750 public String toString() { return s.toString(); } 3751 public int hashCode() { return s.hashCode(); } 3752 public void clear() { s.clear(); } 3753 3754 public boolean add(Map.Entry<K, V> e) { 3755 throw new UnsupportedOperationException(); 3756 } 3757 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) { 3758 throw new UnsupportedOperationException(); 3759 } 3760 3761 public Iterator<Map.Entry<K,V>> iterator() { 3762 final Iterator<Map.Entry<K, V>> i = s.iterator(); 3763 final Class<V> valueType = this.valueType; 3764 3765 return new Iterator<Map.Entry<K,V>>() { 3766 public boolean hasNext() { return i.hasNext(); } 3767 public void remove() { i.remove(); } 3768 3769 public Map.Entry<K,V> next() { 3770 return checkedEntry(i.next(), valueType); 3771 } 3772 }; 3773 } 3774 3775 @SuppressWarnings("unchecked") 3776 public Object[] toArray() { 3777 Object[] source = s.toArray(); 3778 3779 /* 3780 * Ensure that we don't get an ArrayStoreException even if 3781 * s.toArray returns an array of something other than Object 3782 */ 3783 Object[] dest = (CheckedEntry.class.isInstance( 3784 source.getClass().getComponentType()) ? source : 3785 new Object[source.length]); 3786 3787 for (int i = 0; i < source.length; i++) 3788 dest[i] = checkedEntry((Map.Entry<K,V>)source[i], 3789 valueType); 3790 return dest; 3791 } 3792 3793 @SuppressWarnings("unchecked") 3794 public <T> T[] toArray(T[] a) { 3795 // We don't pass a to s.toArray, to avoid window of 3796 // vulnerability wherein an unscrupulous multithreaded client 3797 // could get his hands on raw (unwrapped) Entries from s. 3798 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); 3799 3800 for (int i=0; i<arr.length; i++) 3801 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i], 3802 valueType); 3803 if (arr.length > a.length) 3804 return arr; 3805 3806 System.arraycopy(arr, 0, a, 0, arr.length); 3807 if (a.length > arr.length) 3808 a[arr.length] = null; 3809 return a; 3810 } 3811 3812 /** 3813 * This method is overridden to protect the backing set against 3814 * an object with a nefarious equals function that senses 3815 * that the equality-candidate is Map.Entry and calls its 3816 * setValue method. 3817 */ 3818 public boolean contains(Object o) { 3819 if (!(o instanceof Map.Entry)) 3820 return false; 3821 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 3822 return s.contains( 3823 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType)); 3824 } 3825 3826 /** 3827 * The bulk collection methods are overridden to protect 3828 * against an unscrupulous collection whose contains(Object o) 3829 * method senses when o is a Map.Entry, and calls o.setValue. 3830 */ 3831 public boolean containsAll(Collection<?> c) { 3832 for (Object o : c) 3833 if (!contains(o)) // Invokes safe contains() above 3834 return false; 3835 return true; 3836 } 3837 3838 public boolean remove(Object o) { 3839 if (!(o instanceof Map.Entry)) 3840 return false; 3841 return s.remove(new AbstractMap.SimpleImmutableEntry 3842 <>((Map.Entry<?,?>)o)); 3843 } 3844 3845 public boolean removeAll(Collection<?> c) { 3846 return batchRemove(c, false); 3847 } 3848 public boolean retainAll(Collection<?> c) { 3849 return batchRemove(c, true); 3850 } 3851 private boolean batchRemove(Collection<?> c, boolean complement) { 3852 Objects.requireNonNull(c); 3853 boolean modified = false; 3854 Iterator<Map.Entry<K,V>> it = iterator(); 3855 while (it.hasNext()) { 3856 if (c.contains(it.next()) != complement) { 3857 it.remove(); 3858 modified = true; 3859 } 3860 } 3861 return modified; 3862 } 3863 3864 public boolean equals(Object o) { 3865 if (o == this) 3866 return true; 3867 if (!(o instanceof Set)) 3868 return false; 3869 Set<?> that = (Set<?>) o; 3870 return that.size() == s.size() 3871 && containsAll(that); // Invokes safe containsAll() above 3872 } 3873 3874 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e, 3875 Class<T> valueType) { 3876 return new CheckedEntry<>(e, valueType); 3877 } 3878 3879 /** 3880 * This "wrapper class" serves two purposes: it prevents 3881 * the client from modifying the backing Map, by short-circuiting 3882 * the setValue method, and it protects the backing Map against 3883 * an ill-behaved Map.Entry that attempts to modify another 3884 * Map.Entry when asked to perform an equality check. 3885 */ 3886 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> { 3887 private final Map.Entry<K, V> e; 3888 private final Class<T> valueType; 3889 3890 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) { 3891 this.e = Objects.requireNonNull(e); 3892 this.valueType = Objects.requireNonNull(valueType); 3893 } 3894 3895 public K getKey() { return e.getKey(); } 3896 public V getValue() { return e.getValue(); } 3897 public int hashCode() { return e.hashCode(); } 3898 public String toString() { return e.toString(); } 3899 3900 public V setValue(V value) { 3901 if (value != null && !valueType.isInstance(value)) 3902 throw new ClassCastException(badValueMsg(value)); 3903 return e.setValue(value); 3904 } 3905 3906 private String badValueMsg(Object value) { 3907 return "Attempt to insert " + value.getClass() + 3908 " value into map with value type " + valueType; 3909 } 3910 3911 public boolean equals(Object o) { 3912 if (o == this) 3913 return true; 3914 if (!(o instanceof Map.Entry)) 3915 return false; 3916 return e.equals(new AbstractMap.SimpleImmutableEntry 3917 <>((Map.Entry<?,?>)o)); 3918 } 3919 } 3920 } 3921 } 3922 3923 /** 3924 * Returns a dynamically typesafe view of the specified sorted map. 3925 * Any attempt to insert a mapping whose key or value have the wrong 3926 * type will result in an immediate {@link ClassCastException}. 3927 * Similarly, any attempt to modify the value currently associated with 3928 * a key will result in an immediate {@link ClassCastException}, 3929 * whether the modification is attempted directly through the map 3930 * itself, or through a {@link Map.Entry} instance obtained from the 3931 * map's {@link Map#entrySet() entry set} view. 3932 * 3933 * <p>Assuming a map contains no incorrectly typed keys or values 3934 * prior to the time a dynamically typesafe view is generated, and 3935 * that all subsequent access to the map takes place through the view 3936 * (or one of its collection views), it is <i>guaranteed</i> that the 3937 * map cannot contain an incorrectly typed key or value. 3938 * 3939 * <p>A discussion of the use of dynamically typesafe views may be 3940 * found in the documentation for the {@link #checkedCollection 3941 * checkedCollection} method. 3942 * 3943 * <p>The returned map will be serializable if the specified map is 3944 * serializable. 3945 * 3946 * <p>Since {@code null} is considered to be a value of any reference 3947 * type, the returned map permits insertion of null keys or values 3948 * whenever the backing map does. 3949 * 3950 * @param <K> the class of the map keys 3951 * @param <V> the class of the map values 3952 * @param m the map for which a dynamically typesafe view is to be 3953 * returned 3954 * @param keyType the type of key that {@code m} is permitted to hold 3955 * @param valueType the type of value that {@code m} is permitted to hold 3956 * @return a dynamically typesafe view of the specified map 3957 * @since 1.5 3958 */ 3959 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m, 3960 Class<K> keyType, 3961 Class<V> valueType) { 3962 return new CheckedSortedMap<>(m, keyType, valueType); 3963 } 3964 3965 /** 3966 * @serial include 3967 */ 3968 static class CheckedSortedMap<K,V> extends CheckedMap<K,V> 3969 implements SortedMap<K,V>, Serializable 3970 { 3971 private static final long serialVersionUID = 1599671320688067438L; 3972 3973 private final SortedMap<K, V> sm; 3974 3975 CheckedSortedMap(SortedMap<K, V> m, 3976 Class<K> keyType, Class<V> valueType) { 3977 super(m, keyType, valueType); 3978 sm = m; 3979 } 3980 3981 public Comparator<? super K> comparator() { return sm.comparator(); } 3982 public K firstKey() { return sm.firstKey(); } 3983 public K lastKey() { return sm.lastKey(); } 3984 3985 public SortedMap<K,V> subMap(K fromKey, K toKey) { 3986 return checkedSortedMap(sm.subMap(fromKey, toKey), 3987 keyType, valueType); 3988 } 3989 public SortedMap<K,V> headMap(K toKey) { 3990 return checkedSortedMap(sm.headMap(toKey), keyType, valueType); 3991 } 3992 public SortedMap<K,V> tailMap(K fromKey) { 3993 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType); 3994 } 3995 } 3996 3997 /** 3998 * Returns a dynamically typesafe view of the specified navigable map. 3999 * Any attempt to insert a mapping whose key or value have the wrong 4000 * type will result in an immediate {@link ClassCastException}. 4001 * Similarly, any attempt to modify the value currently associated with 4002 * a key will result in an immediate {@link ClassCastException}, 4003 * whether the modification is attempted directly through the map 4004 * itself, or through a {@link Map.Entry} instance obtained from the 4005 * map's {@link Map#entrySet() entry set} view. 4006 * 4007 * <p>Assuming a map contains no incorrectly typed keys or values 4008 * prior to the time a dynamically typesafe view is generated, and 4009 * that all subsequent access to the map takes place through the view 4010 * (or one of its collection views), it is <em>guaranteed</em> that the 4011 * map cannot contain an incorrectly typed key or value. 4012 * 4013 * <p>A discussion of the use of dynamically typesafe views may be 4014 * found in the documentation for the {@link #checkedCollection 4015 * checkedCollection} method. 4016 * 4017 * <p>The returned map will be serializable if the specified map is 4018 * serializable. 4019 * 4020 * <p>Since {@code null} is considered to be a value of any reference 4021 * type, the returned map permits insertion of null keys or values 4022 * whenever the backing map does. 4023 * 4024 * @param <K> type of map keys 4025 * @param <V> type of map values 4026 * @param m the map for which a dynamically typesafe view is to be 4027 * returned 4028 * @param keyType the type of key that {@code m} is permitted to hold 4029 * @param valueType the type of value that {@code m} is permitted to hold 4030 * @return a dynamically typesafe view of the specified map 4031 * @since 1.8 4032 */ 4033 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m, 4034 Class<K> keyType, 4035 Class<V> valueType) { 4036 return new CheckedNavigableMap<>(m, keyType, valueType); 4037 } 4038 4039 /** 4040 * @serial include 4041 */ 4042 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V> 4043 implements NavigableMap<K,V>, Serializable 4044 { 4045 private static final long serialVersionUID = -4852462692372534096L; 4046 4047 private final NavigableMap<K, V> nm; 4048 4049 CheckedNavigableMap(NavigableMap<K, V> m, 4050 Class<K> keyType, Class<V> valueType) { 4051 super(m, keyType, valueType); 4052 nm = m; 4053 } 4054 4055 public Comparator<? super K> comparator() { return nm.comparator(); } 4056 public K firstKey() { return nm.firstKey(); } 4057 public K lastKey() { return nm.lastKey(); } 4058 4059 public Entry<K, V> lowerEntry(K key) { 4060 Entry<K,V> lower = nm.lowerEntry(key); 4061 return (null != lower) 4062 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(lower, valueType) 4063 : null; 4064 } 4065 4066 public K lowerKey(K key) { return nm.lowerKey(key); } 4067 4068 public Entry<K, V> floorEntry(K key) { 4069 Entry<K,V> floor = nm.floorEntry(key); 4070 return (null != floor) 4071 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(floor, valueType) 4072 : null; 4073 } 4074 4075 public K floorKey(K key) { return nm.floorKey(key); } 4076 4077 public Entry<K, V> ceilingEntry(K key) { 4078 Entry<K,V> ceiling = nm.ceilingEntry(key); 4079 return (null != ceiling) 4080 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(ceiling, valueType) 4081 : null; 4082 } 4083 4084 public K ceilingKey(K key) { return nm.ceilingKey(key); } 4085 4086 public Entry<K, V> higherEntry(K key) { 4087 Entry<K,V> higher = nm.higherEntry(key); 4088 return (null != higher) 4089 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(higher, valueType) 4090 : null; 4091 } 4092 4093 public K higherKey(K key) { return nm.higherKey(key); } 4094 4095 public Entry<K, V> firstEntry() { 4096 Entry<K,V> first = nm.firstEntry(); 4097 return (null != first) 4098 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(first, valueType) 4099 : null; 4100 } 4101 4102 public Entry<K, V> lastEntry() { 4103 Entry<K,V> last = nm.lastEntry(); 4104 return (null != last) 4105 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(last, valueType) 4106 : null; 4107 } 4108 4109 public Entry<K, V> pollFirstEntry() { 4110 Entry<K,V> entry = nm.pollFirstEntry(); 4111 return (null == entry) 4112 ? null 4113 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType); 4114 } 4115 4116 public Entry<K, V> pollLastEntry() { 4117 Entry<K,V> entry = nm.pollLastEntry(); 4118 return (null == entry) 4119 ? null 4120 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType); 4121 } 4122 4123 public NavigableMap<K, V> descendingMap() { 4124 return checkedNavigableMap(nm.descendingMap(), keyType, valueType); 4125 } 4126 4127 public NavigableSet<K> keySet() { 4128 return navigableKeySet(); 4129 } 4130 4131 public NavigableSet<K> navigableKeySet() { 4132 return checkedNavigableSet(nm.navigableKeySet(), keyType); 4133 } 4134 4135 public NavigableSet<K> descendingKeySet() { 4136 return checkedNavigableSet(nm.descendingKeySet(), keyType); 4137 } 4138 4139 @Override 4140 public NavigableMap<K,V> subMap(K fromKey, K toKey) { 4141 return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false), 4142 keyType, valueType); 4143 } 4144 4145 @Override 4146 public NavigableMap<K,V> headMap(K toKey) { 4147 return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType); 4148 } 4149 4150 @Override 4151 public NavigableMap<K,V> tailMap(K fromKey) { 4152 return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType); 4153 } 4154 4155 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 4156 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType); 4157 } 4158 4159 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) { 4160 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType); 4161 } 4162 4163 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) { 4164 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType); 4165 } 4166 } 4167 4168 // Empty collections 4169 4170 /** 4171 * Returns an iterator that has no elements. More precisely, 4172 * 4173 * <ul> 4174 * <li>{@link Iterator#hasNext hasNext} always returns {@code 4175 * false}.</li> 4176 * <li>{@link Iterator#next next} always throws {@link 4177 * NoSuchElementException}.</li> 4178 * <li>{@link Iterator#remove remove} always throws {@link 4179 * IllegalStateException}.</li> 4180 * </ul> 4181 * 4182 * <p>Implementations of this method are permitted, but not 4183 * required, to return the same object from multiple invocations. 4184 * 4185 * @param <T> type of elements, if there were any, in the iterator 4186 * @return an empty iterator 4187 * @since 1.7 4188 */ 4189 @SuppressWarnings("unchecked") 4190 public static <T> Iterator<T> emptyIterator() { 4191 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR; 4192 } 4193 4194 private static class EmptyIterator<E> implements Iterator<E> { 4195 static final EmptyIterator<Object> EMPTY_ITERATOR 4196 = new EmptyIterator<>(); 4197 4198 public boolean hasNext() { return false; } 4199 public E next() { throw new NoSuchElementException(); } 4200 public void remove() { throw new IllegalStateException(); } 4201 @Override 4202 public void forEachRemaining(Consumer<? super E> action) { 4203 Objects.requireNonNull(action); 4204 } 4205 } 4206 4207 /** 4208 * Returns a list iterator that has no elements. More precisely, 4209 * 4210 * <ul> 4211 * <li>{@link Iterator#hasNext hasNext} and {@link 4212 * ListIterator#hasPrevious hasPrevious} always return {@code 4213 * false}.</li> 4214 * <li>{@link Iterator#next next} and {@link ListIterator#previous 4215 * previous} always throw {@link NoSuchElementException}.</li> 4216 * <li>{@link Iterator#remove remove} and {@link ListIterator#set 4217 * set} always throw {@link IllegalStateException}.</li> 4218 * <li>{@link ListIterator#add add} always throws {@link 4219 * UnsupportedOperationException}.</li> 4220 * <li>{@link ListIterator#nextIndex nextIndex} always returns 4221 * {@code 0}.</li> 4222 * <li>{@link ListIterator#previousIndex previousIndex} always 4223 * returns {@code -1}.</li> 4224 * </ul> 4225 * 4226 * <p>Implementations of this method are permitted, but not 4227 * required, to return the same object from multiple invocations. 4228 * 4229 * @param <T> type of elements, if there were any, in the iterator 4230 * @return an empty list iterator 4231 * @since 1.7 4232 */ 4233 @SuppressWarnings("unchecked") 4234 public static <T> ListIterator<T> emptyListIterator() { 4235 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR; 4236 } 4237 4238 private static class EmptyListIterator<E> 4239 extends EmptyIterator<E> 4240 implements ListIterator<E> 4241 { 4242 static final EmptyListIterator<Object> EMPTY_ITERATOR 4243 = new EmptyListIterator<>(); 4244 4245 public boolean hasPrevious() { return false; } 4246 public E previous() { throw new NoSuchElementException(); } 4247 public int nextIndex() { return 0; } 4248 public int previousIndex() { return -1; } 4249 public void set(E e) { throw new IllegalStateException(); } 4250 public void add(E e) { throw new UnsupportedOperationException(); } 4251 } 4252 4253 /** 4254 * Returns an enumeration that has no elements. More precisely, 4255 * 4256 * <ul> 4257 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always 4258 * returns {@code false}.</li> 4259 * <li> {@link Enumeration#nextElement nextElement} always throws 4260 * {@link NoSuchElementException}.</li> 4261 * </ul> 4262 * 4263 * <p>Implementations of this method are permitted, but not 4264 * required, to return the same object from multiple invocations. 4265 * 4266 * @param <T> the class of the objects in the enumeration 4267 * @return an empty enumeration 4268 * @since 1.7 4269 */ 4270 @SuppressWarnings("unchecked") 4271 public static <T> Enumeration<T> emptyEnumeration() { 4272 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION; 4273 } 4274 4275 private static class EmptyEnumeration<E> implements Enumeration<E> { 4276 static final EmptyEnumeration<Object> EMPTY_ENUMERATION 4277 = new EmptyEnumeration<>(); 4278 4279 public boolean hasMoreElements() { return false; } 4280 public E nextElement() { throw new NoSuchElementException(); } 4281 } 4282 4283 /** 4284 * The empty set (immutable). This set is serializable. 4285 * 4286 * @see #emptySet() 4287 */ 4288 @SuppressWarnings("rawtypes") 4289 public static final Set EMPTY_SET = new EmptySet<>(); 4290 4291 /** 4292 * Returns an empty set (immutable). This set is serializable. 4293 * Unlike the like-named field, this method is parameterized. 4294 * 4295 * <p>This example illustrates the type-safe way to obtain an empty set: 4296 * <pre> 4297 * Set<String> s = Collections.emptySet(); 4298 * </pre> 4299 * @implNote Implementations of this method need not create a separate 4300 * {@code Set} object for each call. Using this method is likely to have 4301 * comparable cost to using the like-named field. (Unlike this method, the 4302 * field does not provide type safety.) 4303 * 4304 * @param <T> the class of the objects in the set 4305 * @return the empty set 4306 * 4307 * @see #EMPTY_SET 4308 * @since 1.5 4309 */ 4310 @SuppressWarnings("unchecked") 4311 public static final <T> Set<T> emptySet() { 4312 return (Set<T>) EMPTY_SET; 4313 } 4314 4315 /** 4316 * @serial include 4317 */ 4318 private static class EmptySet<E> 4319 extends AbstractSet<E> 4320 implements Serializable 4321 { 4322 private static final long serialVersionUID = 1582296315990362920L; 4323 4324 public Iterator<E> iterator() { return emptyIterator(); } 4325 4326 public int size() {return 0;} 4327 public boolean isEmpty() {return true;} 4328 4329 public boolean contains(Object obj) {return false;} 4330 public boolean containsAll(Collection<?> c) { return c.isEmpty(); } 4331 4332 public Object[] toArray() { return new Object[0]; } 4333 4334 public <T> T[] toArray(T[] a) { 4335 if (a.length > 0) 4336 a[0] = null; 4337 return a; 4338 } 4339 4340 // Override default methods in Collection 4341 @Override 4342 public void forEach(Consumer<? super E> action) { 4343 Objects.requireNonNull(action); 4344 } 4345 @Override 4346 public boolean removeIf(Predicate<? super E> filter) { 4347 Objects.requireNonNull(filter); 4348 return false; 4349 } 4350 @Override 4351 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); } 4352 4353 // Preserves singleton property 4354 private Object readResolve() { 4355 return EMPTY_SET; 4356 } 4357 } 4358 4359 /** 4360 * Returns an empty sorted set (immutable). This set is serializable. 4361 * 4362 * <p>This example illustrates the type-safe way to obtain an empty 4363 * sorted set: 4364 * <pre> {@code 4365 * SortedSet<String> s = Collections.emptySortedSet(); 4366 * }</pre> 4367 * 4368 * @implNote Implementations of this method need not create a separate 4369 * {@code SortedSet} object for each call. 4370 * 4371 * @param <E> type of elements, if there were any, in the set 4372 * @return the empty sorted set 4373 * @since 1.8 4374 */ 4375 @SuppressWarnings("unchecked") 4376 public static <E> SortedSet<E> emptySortedSet() { 4377 return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET; 4378 } 4379 4380 /** 4381 * Returns an empty navigable set (immutable). This set is serializable. 4382 * 4383 * <p>This example illustrates the type-safe way to obtain an empty 4384 * navigable set: 4385 * <pre> {@code 4386 * NavigableSet<String> s = Collections.emptyNavigableSet(); 4387 * }</pre> 4388 * 4389 * @implNote Implementations of this method need not 4390 * create a separate {@code NavigableSet} object for each call. 4391 * 4392 * @param <E> type of elements, if there were any, in the set 4393 * @return the empty navigable set 4394 * @since 1.8 4395 */ 4396 @SuppressWarnings("unchecked") 4397 public static <E> NavigableSet<E> emptyNavigableSet() { 4398 return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET; 4399 } 4400 4401 /** 4402 * The empty list (immutable). This list is serializable. 4403 * 4404 * @see #emptyList() 4405 */ 4406 @SuppressWarnings("rawtypes") 4407 public static final List EMPTY_LIST = new EmptyList<>(); 4408 4409 /** 4410 * Returns an empty list (immutable). This list is serializable. 4411 * 4412 * <p>This example illustrates the type-safe way to obtain an empty list: 4413 * <pre> 4414 * List<String> s = Collections.emptyList(); 4415 * </pre> 4416 * 4417 * @implNote 4418 * Implementations of this method need not create a separate <tt>List</tt> 4419 * object for each call. Using this method is likely to have comparable 4420 * cost to using the like-named field. (Unlike this method, the field does 4421 * not provide type safety.) 4422 * 4423 * @param <T> type of elements, if there were any, in the list 4424 * @return an empty immutable list 4425 * 4426 * @see #EMPTY_LIST 4427 * @since 1.5 4428 */ 4429 @SuppressWarnings("unchecked") 4430 public static final <T> List<T> emptyList() { 4431 return (List<T>) EMPTY_LIST; 4432 } 4433 4434 /** 4435 * @serial include 4436 */ 4437 private static class EmptyList<E> 4438 extends AbstractList<E> 4439 implements RandomAccess, Serializable { 4440 private static final long serialVersionUID = 8842843931221139166L; 4441 4442 public Iterator<E> iterator() { 4443 return emptyIterator(); 4444 } 4445 public ListIterator<E> listIterator() { 4446 return emptyListIterator(); 4447 } 4448 4449 public int size() {return 0;} 4450 public boolean isEmpty() {return true;} 4451 4452 public boolean contains(Object obj) {return false;} 4453 public boolean containsAll(Collection<?> c) { return c.isEmpty(); } 4454 4455 public Object[] toArray() { return new Object[0]; } 4456 4457 public <T> T[] toArray(T[] a) { 4458 if (a.length > 0) 4459 a[0] = null; 4460 return a; 4461 } 4462 4463 public E get(int index) { 4464 throw new IndexOutOfBoundsException("Index: "+index); 4465 } 4466 4467 public boolean equals(Object o) { 4468 return (o instanceof List) && ((List<?>)o).isEmpty(); 4469 } 4470 4471 public int hashCode() { return 1; } 4472 4473 @Override 4474 public boolean removeIf(Predicate<? super E> filter) { 4475 Objects.requireNonNull(filter); 4476 return false; 4477 } 4478 @Override 4479 public void replaceAll(UnaryOperator<E> operator) { 4480 Objects.requireNonNull(operator); 4481 } 4482 @Override 4483 public void sort(Comparator<? super E> c) { 4484 } 4485 4486 // Override default methods in Collection 4487 @Override 4488 public void forEach(Consumer<? super E> action) { 4489 Objects.requireNonNull(action); 4490 } 4491 4492 @Override 4493 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); } 4494 4495 // Preserves singleton property 4496 private Object readResolve() { 4497 return EMPTY_LIST; 4498 } 4499 } 4500 4501 /** 4502 * The empty map (immutable). This map is serializable. 4503 * 4504 * @see #emptyMap() 4505 * @since 1.3 4506 */ 4507 @SuppressWarnings("rawtypes") 4508 public static final Map EMPTY_MAP = new EmptyMap<>(); 4509 4510 /** 4511 * Returns an empty map (immutable). This map is serializable. 4512 * 4513 * <p>This example illustrates the type-safe way to obtain an empty map: 4514 * <pre> 4515 * Map<String, Date> s = Collections.emptyMap(); 4516 * </pre> 4517 * @implNote Implementations of this method need not create a separate 4518 * {@code Map} object for each call. Using this method is likely to have 4519 * comparable cost to using the like-named field. (Unlike this method, the 4520 * field does not provide type safety.) 4521 * 4522 * @param <K> the class of the map keys 4523 * @param <V> the class of the map values 4524 * @return an empty map 4525 * @see #EMPTY_MAP 4526 * @since 1.5 4527 */ 4528 @SuppressWarnings("unchecked") 4529 public static final <K,V> Map<K,V> emptyMap() { 4530 return (Map<K,V>) EMPTY_MAP; 4531 } 4532 4533 /** 4534 * Returns an empty sorted map (immutable). This map is serializable. 4535 * 4536 * <p>This example illustrates the type-safe way to obtain an empty map: 4537 * <pre> {@code 4538 * SortedMap<String, Date> s = Collections.emptySortedMap(); 4539 * }</pre> 4540 * 4541 * @implNote Implementations of this method need not create a separate 4542 * {@code SortedMap} object for each call. 4543 * 4544 * @param <K> the class of the map keys 4545 * @param <V> the class of the map values 4546 * @return an empty sorted map 4547 * @since 1.8 4548 */ 4549 @SuppressWarnings("unchecked") 4550 public static final <K,V> SortedMap<K,V> emptySortedMap() { 4551 return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP; 4552 } 4553 4554 /** 4555 * Returns an empty navigable map (immutable). This map is serializable. 4556 * 4557 * <p>This example illustrates the type-safe way to obtain an empty map: 4558 * <pre> {@code 4559 * NavigableMap<String, Date> s = Collections.emptyNavigableMap(); 4560 * }</pre> 4561 * 4562 * @implNote Implementations of this method need not create a separate 4563 * {@code NavigableMap} object for each call. 4564 * 4565 * @param <K> the class of the map keys 4566 * @param <V> the class of the map values 4567 * @return an empty navigable map 4568 * @since 1.8 4569 */ 4570 @SuppressWarnings("unchecked") 4571 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() { 4572 return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP; 4573 } 4574 4575 /** 4576 * @serial include 4577 */ 4578 private static class EmptyMap<K,V> 4579 extends AbstractMap<K,V> 4580 implements Serializable 4581 { 4582 private static final long serialVersionUID = 6428348081105594320L; 4583 4584 public int size() {return 0;} 4585 public boolean isEmpty() {return true;} 4586 public boolean containsKey(Object key) {return false;} 4587 public boolean containsValue(Object value) {return false;} 4588 public V get(Object key) {return null;} 4589 public Set<K> keySet() {return emptySet();} 4590 public Collection<V> values() {return emptySet();} 4591 public Set<Map.Entry<K,V>> entrySet() {return emptySet();} 4592 4593 public boolean equals(Object o) { 4594 return (o instanceof Map) && ((Map<?,?>)o).isEmpty(); 4595 } 4596 4597 public int hashCode() {return 0;} 4598 4599 // Override default methods in Map 4600 @Override 4601 @SuppressWarnings("unchecked") 4602 public V getOrDefault(Object k, V defaultValue) { 4603 return defaultValue; 4604 } 4605 4606 @Override 4607 public void forEach(BiConsumer<? super K, ? super V> action) { 4608 Objects.requireNonNull(action); 4609 } 4610 4611 @Override 4612 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 4613 Objects.requireNonNull(function); 4614 } 4615 4616 @Override 4617 public V putIfAbsent(K key, V value) { 4618 throw new UnsupportedOperationException(); 4619 } 4620 4621 @Override 4622 public boolean remove(Object key, Object value) { 4623 throw new UnsupportedOperationException(); 4624 } 4625 4626 @Override 4627 public boolean replace(K key, V oldValue, V newValue) { 4628 throw new UnsupportedOperationException(); 4629 } 4630 4631 @Override 4632 public V replace(K key, V value) { 4633 throw new UnsupportedOperationException(); 4634 } 4635 4636 @Override 4637 public V computeIfAbsent(K key, 4638 Function<? super K, ? extends V> mappingFunction) { 4639 throw new UnsupportedOperationException(); 4640 } 4641 4642 @Override 4643 public V computeIfPresent(K key, 4644 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4645 throw new UnsupportedOperationException(); 4646 } 4647 4648 @Override 4649 public V compute(K key, 4650 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4651 throw new UnsupportedOperationException(); 4652 } 4653 4654 @Override 4655 public V merge(K key, V value, 4656 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 4657 throw new UnsupportedOperationException(); 4658 } 4659 4660 // Preserves singleton property 4661 private Object readResolve() { 4662 return EMPTY_MAP; 4663 } 4664 } 4665 4666 // Singleton collections 4667 4668 /** 4669 * Returns an immutable set containing only the specified object. 4670 * The returned set is serializable. 4671 * 4672 * @param <T> the class of the objects in the set 4673 * @param o the sole object to be stored in the returned set. 4674 * @return an immutable set containing only the specified object. 4675 */ 4676 public static <T> Set<T> singleton(T o) { 4677 return new SingletonSet<>(o); 4678 } 4679 4680 static <E> Iterator<E> singletonIterator(final E e) { 4681 return new Iterator<E>() { 4682 private boolean hasNext = true; 4683 public boolean hasNext() { 4684 return hasNext; 4685 } 4686 public E next() { 4687 if (hasNext) { 4688 hasNext = false; 4689 return e; 4690 } 4691 throw new NoSuchElementException(); 4692 } 4693 public void remove() { 4694 throw new UnsupportedOperationException(); 4695 } 4696 @Override 4697 public void forEachRemaining(Consumer<? super E> action) { 4698 Objects.requireNonNull(action); 4699 if (hasNext) { 4700 action.accept(e); 4701 hasNext = false; 4702 } 4703 } 4704 }; 4705 } 4706 4707 /** 4708 * Creates a {@code Spliterator} with only the specified element 4709 * 4710 * @param <T> Type of elements 4711 * @return A singleton {@code Spliterator} 4712 */ 4713 static <T> Spliterator<T> singletonSpliterator(final T element) { 4714 return new Spliterator<T>() { 4715 long est = 1; 4716 4717 @Override 4718 public Spliterator<T> trySplit() { 4719 return null; 4720 } 4721 4722 @Override 4723 public boolean tryAdvance(Consumer<? super T> consumer) { 4724 Objects.requireNonNull(consumer); 4725 if (est > 0) { 4726 est--; 4727 consumer.accept(element); 4728 return true; 4729 } 4730 return false; 4731 } 4732 4733 @Override 4734 public void forEachRemaining(Consumer<? super T> consumer) { 4735 tryAdvance(consumer); 4736 } 4737 4738 @Override 4739 public long estimateSize() { 4740 return est; 4741 } 4742 4743 @Override 4744 public int characteristics() { 4745 int value = (element != null) ? Spliterator.NONNULL : 0; 4746 4747 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE | 4748 Spliterator.DISTINCT | Spliterator.ORDERED; 4749 } 4750 }; 4751 } 4752 4753 /** 4754 * @serial include 4755 */ 4756 private static class SingletonSet<E> 4757 extends AbstractSet<E> 4758 implements Serializable 4759 { 4760 private static final long serialVersionUID = 3193687207550431679L; 4761 4762 private final E element; 4763 4764 SingletonSet(E e) {element = e;} 4765 4766 public Iterator<E> iterator() { 4767 return singletonIterator(element); 4768 } 4769 4770 public int size() {return 1;} 4771 4772 public boolean contains(Object o) {return eq(o, element);} 4773 4774 // Override default methods for Collection 4775 @Override 4776 public void forEach(Consumer<? super E> action) { 4777 action.accept(element); 4778 } 4779 @Override 4780 public Spliterator<E> spliterator() { 4781 return singletonSpliterator(element); 4782 } 4783 @Override 4784 public boolean removeIf(Predicate<? super E> filter) { 4785 throw new UnsupportedOperationException(); 4786 } 4787 } 4788 4789 /** 4790 * Returns an immutable list containing only the specified object. 4791 * The returned list is serializable. 4792 * 4793 * @param <T> the class of the objects in the list 4794 * @param o the sole object to be stored in the returned list. 4795 * @return an immutable list containing only the specified object. 4796 * @since 1.3 4797 */ 4798 public static <T> List<T> singletonList(T o) { 4799 return new SingletonList<>(o); 4800 } 4801 4802 /** 4803 * @serial include 4804 */ 4805 private static class SingletonList<E> 4806 extends AbstractList<E> 4807 implements RandomAccess, Serializable { 4808 4809 private static final long serialVersionUID = 3093736618740652951L; 4810 4811 private final E element; 4812 4813 SingletonList(E obj) {element = obj;} 4814 4815 public Iterator<E> iterator() { 4816 return singletonIterator(element); 4817 } 4818 4819 public int size() {return 1;} 4820 4821 public boolean contains(Object obj) {return eq(obj, element);} 4822 4823 public E get(int index) { 4824 if (index != 0) 4825 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1"); 4826 return element; 4827 } 4828 4829 // Override default methods for Collection 4830 @Override 4831 public void forEach(Consumer<? super E> action) { 4832 action.accept(element); 4833 } 4834 @Override 4835 public boolean removeIf(Predicate<? super E> filter) { 4836 throw new UnsupportedOperationException(); 4837 } 4838 @Override 4839 public void replaceAll(UnaryOperator<E> operator) { 4840 throw new UnsupportedOperationException(); 4841 } 4842 @Override 4843 public void sort(Comparator<? super E> c) { 4844 } 4845 @Override 4846 public Spliterator<E> spliterator() { 4847 return singletonSpliterator(element); 4848 } 4849 } 4850 4851 /** 4852 * Returns an immutable map, mapping only the specified key to the 4853 * specified value. The returned map is serializable. 4854 * 4855 * @param <K> the class of the map keys 4856 * @param <V> the class of the map values 4857 * @param key the sole key to be stored in the returned map. 4858 * @param value the value to which the returned map maps <tt>key</tt>. 4859 * @return an immutable map containing only the specified key-value 4860 * mapping. 4861 * @since 1.3 4862 */ 4863 public static <K,V> Map<K,V> singletonMap(K key, V value) { 4864 return new SingletonMap<>(key, value); 4865 } 4866 4867 /** 4868 * @serial include 4869 */ 4870 private static class SingletonMap<K,V> 4871 extends AbstractMap<K,V> 4872 implements Serializable { 4873 private static final long serialVersionUID = -6979724477215052911L; 4874 4875 private final K k; 4876 private final V v; 4877 4878 SingletonMap(K key, V value) { 4879 k = key; 4880 v = value; 4881 } 4882 4883 public int size() {return 1;} 4884 public boolean isEmpty() {return false;} 4885 public boolean containsKey(Object key) {return eq(key, k);} 4886 public boolean containsValue(Object value) {return eq(value, v);} 4887 public V get(Object key) {return (eq(key, k) ? v : null);} 4888 4889 private transient Set<K> keySet; 4890 private transient Set<Map.Entry<K,V>> entrySet; 4891 private transient Collection<V> values; 4892 4893 public Set<K> keySet() { 4894 if (keySet==null) 4895 keySet = singleton(k); 4896 return keySet; 4897 } 4898 4899 public Set<Map.Entry<K,V>> entrySet() { 4900 if (entrySet==null) 4901 entrySet = Collections.<Map.Entry<K,V>>singleton( 4902 new SimpleImmutableEntry<>(k, v)); 4903 return entrySet; 4904 } 4905 4906 public Collection<V> values() { 4907 if (values==null) 4908 values = singleton(v); 4909 return values; 4910 } 4911 4912 // Override default methods in Map 4913 @Override 4914 public V getOrDefault(Object key, V defaultValue) { 4915 return eq(key, k) ? v : defaultValue; 4916 } 4917 4918 @Override 4919 public void forEach(BiConsumer<? super K, ? super V> action) { 4920 action.accept(k, v); 4921 } 4922 4923 @Override 4924 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 4925 throw new UnsupportedOperationException(); 4926 } 4927 4928 @Override 4929 public V putIfAbsent(K key, V value) { 4930 throw new UnsupportedOperationException(); 4931 } 4932 4933 @Override 4934 public boolean remove(Object key, Object value) { 4935 throw new UnsupportedOperationException(); 4936 } 4937 4938 @Override 4939 public boolean replace(K key, V oldValue, V newValue) { 4940 throw new UnsupportedOperationException(); 4941 } 4942 4943 @Override 4944 public V replace(K key, V value) { 4945 throw new UnsupportedOperationException(); 4946 } 4947 4948 @Override 4949 public V computeIfAbsent(K key, 4950 Function<? super K, ? extends V> mappingFunction) { 4951 throw new UnsupportedOperationException(); 4952 } 4953 4954 @Override 4955 public V computeIfPresent(K key, 4956 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4957 throw new UnsupportedOperationException(); 4958 } 4959 4960 @Override 4961 public V compute(K key, 4962 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4963 throw new UnsupportedOperationException(); 4964 } 4965 4966 @Override 4967 public V merge(K key, V value, 4968 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 4969 throw new UnsupportedOperationException(); 4970 } 4971 } 4972 4973 // Miscellaneous 4974 4975 /** 4976 * Returns an immutable list consisting of <tt>n</tt> copies of the 4977 * specified object. The newly allocated data object is tiny (it contains 4978 * a single reference to the data object). This method is useful in 4979 * combination with the <tt>List.addAll</tt> method to grow lists. 4980 * The returned list is serializable. 4981 * 4982 * @param <T> the class of the object to copy and of the objects 4983 * in the returned list. 4984 * @param n the number of elements in the returned list. 4985 * @param o the element to appear repeatedly in the returned list. 4986 * @return an immutable list consisting of <tt>n</tt> copies of the 4987 * specified object. 4988 * @throws IllegalArgumentException if {@code n < 0} 4989 * @see List#addAll(Collection) 4990 * @see List#addAll(int, Collection) 4991 */ 4992 public static <T> List<T> nCopies(int n, T o) { 4993 if (n < 0) 4994 throw new IllegalArgumentException("List length = " + n); 4995 return new CopiesList<>(n, o); 4996 } 4997 4998 /** 4999 * @serial include 5000 */ 5001 private static class CopiesList<E> 5002 extends AbstractList<E> 5003 implements RandomAccess, Serializable 5004 { 5005 private static final long serialVersionUID = 2739099268398711800L; 5006 5007 final int n; 5008 final E element; 5009 5010 CopiesList(int n, E e) { 5011 assert n >= 0; 5012 this.n = n; 5013 element = e; 5014 } 5015 5016 public int size() { 5017 return n; 5018 } 5019 5020 public boolean contains(Object obj) { 5021 return n != 0 && eq(obj, element); 5022 } 5023 5024 public int indexOf(Object o) { 5025 return contains(o) ? 0 : -1; 5026 } 5027 5028 public int lastIndexOf(Object o) { 5029 return contains(o) ? n - 1 : -1; 5030 } 5031 5032 public E get(int index) { 5033 if (index < 0 || index >= n) 5034 throw new IndexOutOfBoundsException("Index: "+index+ 5035 ", Size: "+n); 5036 return element; 5037 } 5038 5039 public Object[] toArray() { 5040 final Object[] a = new Object[n]; 5041 if (element != null) 5042 Arrays.fill(a, 0, n, element); 5043 return a; 5044 } 5045 5046 @SuppressWarnings("unchecked") 5047 public <T> T[] toArray(T[] a) { 5048 final int n = this.n; 5049 if (a.length < n) { 5050 a = (T[])java.lang.reflect.Array 5051 .newInstance(a.getClass().getComponentType(), n); 5052 if (element != null) 5053 Arrays.fill(a, 0, n, element); 5054 } else { 5055 Arrays.fill(a, 0, n, element); 5056 if (a.length > n) 5057 a[n] = null; 5058 } 5059 return a; 5060 } 5061 5062 public List<E> subList(int fromIndex, int toIndex) { 5063 if (fromIndex < 0) 5064 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex); 5065 if (toIndex > n) 5066 throw new IndexOutOfBoundsException("toIndex = " + toIndex); 5067 if (fromIndex > toIndex) 5068 throw new IllegalArgumentException("fromIndex(" + fromIndex + 5069 ") > toIndex(" + toIndex + ")"); 5070 return new CopiesList<>(toIndex - fromIndex, element); 5071 } 5072 5073 // Override default methods in Collection 5074 @Override 5075 public Stream<E> stream() { 5076 return IntStream.range(0, n).mapToObj(i -> element); 5077 } 5078 5079 @Override 5080 public Stream<E> parallelStream() { 5081 return IntStream.range(0, n).parallel().mapToObj(i -> element); 5082 } 5083 5084 @Override 5085 public Spliterator<E> spliterator() { 5086 return stream().spliterator(); 5087 } 5088 } 5089 5090 /** 5091 * Returns a comparator that imposes the reverse of the <em>natural 5092 * ordering</em> on a collection of objects that implement the 5093 * {@code Comparable} interface. (The natural ordering is the ordering 5094 * imposed by the objects' own {@code compareTo} method.) This enables a 5095 * simple idiom for sorting (or maintaining) collections (or arrays) of 5096 * objects that implement the {@code Comparable} interface in 5097 * reverse-natural-order. For example, suppose {@code a} is an array of 5098 * strings. Then: <pre> 5099 * Arrays.sort(a, Collections.reverseOrder()); 5100 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p> 5101 * 5102 * The returned comparator is serializable. 5103 * 5104 * @param <T> the class of the objects compared by the comparator 5105 * @return A comparator that imposes the reverse of the <i>natural 5106 * ordering</i> on a collection of objects that implement 5107 * the <tt>Comparable</tt> interface. 5108 * @see Comparable 5109 */ 5110 @SuppressWarnings("unchecked") 5111 public static <T> Comparator<T> reverseOrder() { 5112 return (Comparator<T>) ReverseComparator.REVERSE_ORDER; 5113 } 5114 5115 /** 5116 * @serial include 5117 */ 5118 private static class ReverseComparator 5119 implements Comparator<Comparable<Object>>, Serializable { 5120 5121 private static final long serialVersionUID = 7207038068494060240L; 5122 5123 static final ReverseComparator REVERSE_ORDER 5124 = new ReverseComparator(); 5125 5126 public int compare(Comparable<Object> c1, Comparable<Object> c2) { 5127 return c2.compareTo(c1); 5128 } 5129 5130 private Object readResolve() { return Collections.reverseOrder(); } 5131 5132 @Override 5133 public Comparator<Comparable<Object>> reversed() { 5134 return Comparator.naturalOrder(); 5135 } 5136 } 5137 5138 /** 5139 * Returns a comparator that imposes the reverse ordering of the specified 5140 * comparator. If the specified comparator is {@code null}, this method is 5141 * equivalent to {@link #reverseOrder()} (in other words, it returns a 5142 * comparator that imposes the reverse of the <em>natural ordering</em> on 5143 * a collection of objects that implement the Comparable interface). 5144 * 5145 * <p>The returned comparator is serializable (assuming the specified 5146 * comparator is also serializable or {@code null}). 5147 * 5148 * @param <T> the class of the objects compared by the comparator 5149 * @param cmp a comparator who's ordering is to be reversed by the returned 5150 * comparator or {@code null} 5151 * @return A comparator that imposes the reverse ordering of the 5152 * specified comparator. 5153 * @since 1.5 5154 */ 5155 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) { 5156 if (cmp == null) 5157 return reverseOrder(); 5158 5159 if (cmp instanceof ReverseComparator2) 5160 return ((ReverseComparator2<T>)cmp).cmp; 5161 5162 return new ReverseComparator2<>(cmp); 5163 } 5164 5165 /** 5166 * @serial include 5167 */ 5168 private static class ReverseComparator2<T> implements Comparator<T>, 5169 Serializable 5170 { 5171 private static final long serialVersionUID = 4374092139857L; 5172 5173 /** 5174 * The comparator specified in the static factory. This will never 5175 * be null, as the static factory returns a ReverseComparator 5176 * instance if its argument is null. 5177 * 5178 * @serial 5179 */ 5180 final Comparator<T> cmp; 5181 5182 ReverseComparator2(Comparator<T> cmp) { 5183 assert cmp != null; 5184 this.cmp = cmp; 5185 } 5186 5187 public int compare(T t1, T t2) { 5188 return cmp.compare(t2, t1); 5189 } 5190 5191 public boolean equals(Object o) { 5192 return (o == this) || 5193 (o instanceof ReverseComparator2 && 5194 cmp.equals(((ReverseComparator2)o).cmp)); 5195 } 5196 5197 public int hashCode() { 5198 return cmp.hashCode() ^ Integer.MIN_VALUE; 5199 } 5200 5201 @Override 5202 public Comparator<T> reversed() { 5203 return cmp; 5204 } 5205 } 5206 5207 /** 5208 * Returns an enumeration over the specified collection. This provides 5209 * interoperability with legacy APIs that require an enumeration 5210 * as input. 5211 * 5212 * @param <T> the class of the objects in the collection 5213 * @param c the collection for which an enumeration is to be returned. 5214 * @return an enumeration over the specified collection. 5215 * @see Enumeration 5216 */ 5217 public static <T> Enumeration<T> enumeration(final Collection<T> c) { 5218 return new Enumeration<T>() { 5219 private final Iterator<T> i = c.iterator(); 5220 5221 public boolean hasMoreElements() { 5222 return i.hasNext(); 5223 } 5224 5225 public T nextElement() { 5226 return i.next(); 5227 } 5228 }; 5229 } 5230 5231 /** 5232 * Returns an array list containing the elements returned by the 5233 * specified enumeration in the order they are returned by the 5234 * enumeration. This method provides interoperability between 5235 * legacy APIs that return enumerations and new APIs that require 5236 * collections. 5237 * 5238 * @param <T> the class of the objects returned by the enumeration 5239 * @param e enumeration providing elements for the returned 5240 * array list 5241 * @return an array list containing the elements returned 5242 * by the specified enumeration. 5243 * @since 1.4 5244 * @see Enumeration 5245 * @see ArrayList 5246 */ 5247 public static <T> ArrayList<T> list(Enumeration<T> e) { 5248 ArrayList<T> l = new ArrayList<>(); 5249 while (e.hasMoreElements()) 5250 l.add(e.nextElement()); 5251 return l; 5252 } 5253 5254 /** 5255 * Returns true if the specified arguments are equal, or both null. 5256 * 5257 * NB: Do not replace with Object.equals until JDK-8015417 is resolved. 5258 */ 5259 static boolean eq(Object o1, Object o2) { 5260 return o1==null ? o2==null : o1.equals(o2); 5261 } 5262 5263 /** 5264 * Returns the number of elements in the specified collection equal to the 5265 * specified object. More formally, returns the number of elements 5266 * <tt>e</tt> in the collection such that 5267 * <tt>(o == null ? e == null : o.equals(e))</tt>. 5268 * 5269 * @param c the collection in which to determine the frequency 5270 * of <tt>o</tt> 5271 * @param o the object whose frequency is to be determined 5272 * @return the number of elements in {@code c} equal to {@code o} 5273 * @throws NullPointerException if <tt>c</tt> is null 5274 * @since 1.5 5275 */ 5276 public static int frequency(Collection<?> c, Object o) { 5277 int result = 0; 5278 if (o == null) { 5279 for (Object e : c) 5280 if (e == null) 5281 result++; 5282 } else { 5283 for (Object e : c) 5284 if (o.equals(e)) 5285 result++; 5286 } 5287 return result; 5288 } 5289 5290 /** 5291 * Returns {@code true} if the two specified collections have no 5292 * elements in common. 5293 * 5294 * <p>Care must be exercised if this method is used on collections that 5295 * do not comply with the general contract for {@code Collection}. 5296 * Implementations may elect to iterate over either collection and test 5297 * for containment in the other collection (or to perform any equivalent 5298 * computation). If either collection uses a nonstandard equality test 5299 * (as does a {@link SortedSet} whose ordering is not <em>compatible with 5300 * equals</em>, or the key set of an {@link IdentityHashMap}), both 5301 * collections must use the same nonstandard equality test, or the 5302 * result of this method is undefined. 5303 * 5304 * <p>Care must also be exercised when using collections that have 5305 * restrictions on the elements that they may contain. Collection 5306 * implementations are allowed to throw exceptions for any operation 5307 * involving elements they deem ineligible. For absolute safety the 5308 * specified collections should contain only elements which are 5309 * eligible elements for both collections. 5310 * 5311 * <p>Note that it is permissible to pass the same collection in both 5312 * parameters, in which case the method will return {@code true} if and 5313 * only if the collection is empty. 5314 * 5315 * @param c1 a collection 5316 * @param c2 a collection 5317 * @return {@code true} if the two specified collections have no 5318 * elements in common. 5319 * @throws NullPointerException if either collection is {@code null}. 5320 * @throws NullPointerException if one collection contains a {@code null} 5321 * element and {@code null} is not an eligible element for the other collection. 5322 * (<a href="Collection.html#optional-restrictions">optional</a>) 5323 * @throws ClassCastException if one collection contains an element that is 5324 * of a type which is ineligible for the other collection. 5325 * (<a href="Collection.html#optional-restrictions">optional</a>) 5326 * @since 1.5 5327 */ 5328 public static boolean disjoint(Collection<?> c1, Collection<?> c2) { 5329 // The collection to be used for contains(). Preference is given to 5330 // the collection who's contains() has lower O() complexity. 5331 Collection<?> contains = c2; 5332 // The collection to be iterated. If the collections' contains() impl 5333 // are of different O() complexity, the collection with slower 5334 // contains() will be used for iteration. For collections who's 5335 // contains() are of the same complexity then best performance is 5336 // achieved by iterating the smaller collection. 5337 Collection<?> iterate = c1; 5338 5339 // Performance optimization cases. The heuristics: 5340 // 1. Generally iterate over c1. 5341 // 2. If c1 is a Set then iterate over c2. 5342 // 3. If either collection is empty then result is always true. 5343 // 4. Iterate over the smaller Collection. 5344 if (c1 instanceof Set) { 5345 // Use c1 for contains as a Set's contains() is expected to perform 5346 // better than O(N/2) 5347 iterate = c2; 5348 contains = c1; 5349 } else if (!(c2 instanceof Set)) { 5350 // Both are mere Collections. Iterate over smaller collection. 5351 // Example: If c1 contains 3 elements and c2 contains 50 elements and 5352 // assuming contains() requires ceiling(N/2) comparisons then 5353 // checking for all c1 elements in c2 would require 75 comparisons 5354 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring 5355 // 100 comparisons (50 * ceiling(3/2)). 5356 int c1size = c1.size(); 5357 int c2size = c2.size(); 5358 if (c1size == 0 || c2size == 0) { 5359 // At least one collection is empty. Nothing will match. 5360 return true; 5361 } 5362 5363 if (c1size > c2size) { 5364 iterate = c2; 5365 contains = c1; 5366 } 5367 } 5368 5369 for (Object e : iterate) { 5370 if (contains.contains(e)) { 5371 // Found a common element. Collections are not disjoint. 5372 return false; 5373 } 5374 } 5375 5376 // No common elements were found. 5377 return true; 5378 } 5379 5380 /** 5381 * Adds all of the specified elements to the specified collection. 5382 * Elements to be added may be specified individually or as an array. 5383 * The behavior of this convenience method is identical to that of 5384 * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely 5385 * to run significantly faster under most implementations. 5386 * 5387 * <p>When elements are specified individually, this method provides a 5388 * convenient way to add a few elements to an existing collection: 5389 * <pre> 5390 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon"); 5391 * </pre> 5392 * 5393 * @param <T> the class of the elements to add and of the collection 5394 * @param c the collection into which <tt>elements</tt> are to be inserted 5395 * @param elements the elements to insert into <tt>c</tt> 5396 * @return <tt>true</tt> if the collection changed as a result of the call 5397 * @throws UnsupportedOperationException if <tt>c</tt> does not support 5398 * the <tt>add</tt> operation 5399 * @throws NullPointerException if <tt>elements</tt> contains one or more 5400 * null values and <tt>c</tt> does not permit null elements, or 5401 * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt> 5402 * @throws IllegalArgumentException if some property of a value in 5403 * <tt>elements</tt> prevents it from being added to <tt>c</tt> 5404 * @see Collection#addAll(Collection) 5405 * @since 1.5 5406 */ 5407 @SafeVarargs 5408 public static <T> boolean addAll(Collection<? super T> c, T... elements) { 5409 boolean result = false; 5410 for (T element : elements) 5411 result |= c.add(element); 5412 return result; 5413 } 5414 5415 /** 5416 * Returns a set backed by the specified map. The resulting set displays 5417 * the same ordering, concurrency, and performance characteristics as the 5418 * backing map. In essence, this factory method provides a {@link Set} 5419 * implementation corresponding to any {@link Map} implementation. There 5420 * is no need to use this method on a {@link Map} implementation that 5421 * already has a corresponding {@link Set} implementation (such as {@link 5422 * HashMap} or {@link TreeMap}). 5423 * 5424 * <p>Each method invocation on the set returned by this method results in 5425 * exactly one method invocation on the backing map or its <tt>keySet</tt> 5426 * view, with one exception. The <tt>addAll</tt> method is implemented 5427 * as a sequence of <tt>put</tt> invocations on the backing map. 5428 * 5429 * <p>The specified map must be empty at the time this method is invoked, 5430 * and should not be accessed directly after this method returns. These 5431 * conditions are ensured if the map is created empty, passed directly 5432 * to this method, and no reference to the map is retained, as illustrated 5433 * in the following code fragment: 5434 * <pre> 5435 * Set<Object> weakHashSet = Collections.newSetFromMap( 5436 * new WeakHashMap<Object, Boolean>()); 5437 * </pre> 5438 * 5439 * @param <E> the class of the map keys and of the objects in the 5440 * returned set 5441 * @param map the backing map 5442 * @return the set backed by the map 5443 * @throws IllegalArgumentException if <tt>map</tt> is not empty 5444 * @since 1.6 5445 */ 5446 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) { 5447 return new SetFromMap<>(map); 5448 } 5449 5450 /** 5451 * @serial include 5452 */ 5453 private static class SetFromMap<E> extends AbstractSet<E> 5454 implements Set<E>, Serializable 5455 { 5456 private final Map<E, Boolean> m; // The backing map 5457 private transient Set<E> s; // Its keySet 5458 5459 SetFromMap(Map<E, Boolean> map) { 5460 if (!map.isEmpty()) 5461 throw new IllegalArgumentException("Map is non-empty"); 5462 m = map; 5463 s = map.keySet(); 5464 } 5465 5466 public void clear() { m.clear(); } 5467 public int size() { return m.size(); } 5468 public boolean isEmpty() { return m.isEmpty(); } 5469 public boolean contains(Object o) { return m.containsKey(o); } 5470 public boolean remove(Object o) { return m.remove(o) != null; } 5471 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; } 5472 public Iterator<E> iterator() { return s.iterator(); } 5473 public Object[] toArray() { return s.toArray(); } 5474 public <T> T[] toArray(T[] a) { return s.toArray(a); } 5475 public String toString() { return s.toString(); } 5476 public int hashCode() { return s.hashCode(); } 5477 public boolean equals(Object o) { return o == this || s.equals(o); } 5478 public boolean containsAll(Collection<?> c) {return s.containsAll(c);} 5479 public boolean removeAll(Collection<?> c) {return s.removeAll(c);} 5480 public boolean retainAll(Collection<?> c) {return s.retainAll(c);} 5481 // addAll is the only inherited implementation 5482 5483 // Override default methods in Collection 5484 @Override 5485 public void forEach(Consumer<? super E> action) { 5486 s.forEach(action); 5487 } 5488 @Override 5489 public boolean removeIf(Predicate<? super E> filter) { 5490 return s.removeIf(filter); 5491 } 5492 5493 @Override 5494 public Spliterator<E> spliterator() {return s.spliterator();} 5495 @Override 5496 public Stream<E> stream() {return s.stream();} 5497 @Override 5498 public Stream<E> parallelStream() {return s.parallelStream();} 5499 5500 private static final long serialVersionUID = 2454657854757543876L; 5501 5502 private void readObject(java.io.ObjectInputStream stream) 5503 throws IOException, ClassNotFoundException 5504 { 5505 stream.defaultReadObject(); 5506 s = m.keySet(); 5507 } 5508 } 5509 5510 /** 5511 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo) 5512 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>, 5513 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This 5514 * view can be useful when you would like to use a method 5515 * requiring a <tt>Queue</tt> but you need Lifo ordering. 5516 * 5517 * <p>Each method invocation on the queue returned by this method 5518 * results in exactly one method invocation on the backing deque, with 5519 * one exception. The {@link Queue#addAll addAll} method is 5520 * implemented as a sequence of {@link Deque#addFirst addFirst} 5521 * invocations on the backing deque. 5522 * 5523 * @param <T> the class of the objects in the deque 5524 * @param deque the deque 5525 * @return the queue 5526 * @since 1.6 5527 */ 5528 public static <T> Queue<T> asLifoQueue(Deque<T> deque) { 5529 return new AsLIFOQueue<>(deque); 5530 } 5531 5532 /** 5533 * @serial include 5534 */ 5535 static class AsLIFOQueue<E> extends AbstractQueue<E> 5536 implements Queue<E>, Serializable { 5537 private static final long serialVersionUID = 1802017725587941708L; 5538 private final Deque<E> q; 5539 AsLIFOQueue(Deque<E> q) { this.q = q; } 5540 public boolean add(E e) { q.addFirst(e); return true; } 5541 public boolean offer(E e) { return q.offerFirst(e); } 5542 public E poll() { return q.pollFirst(); } 5543 public E remove() { return q.removeFirst(); } 5544 public E peek() { return q.peekFirst(); } 5545 public E element() { return q.getFirst(); } 5546 public void clear() { q.clear(); } 5547 public int size() { return q.size(); } 5548 public boolean isEmpty() { return q.isEmpty(); } 5549 public boolean contains(Object o) { return q.contains(o); } 5550 public boolean remove(Object o) { return q.remove(o); } 5551 public Iterator<E> iterator() { return q.iterator(); } 5552 public Object[] toArray() { return q.toArray(); } 5553 public <T> T[] toArray(T[] a) { return q.toArray(a); } 5554 public String toString() { return q.toString(); } 5555 public boolean containsAll(Collection<?> c) {return q.containsAll(c);} 5556 public boolean removeAll(Collection<?> c) {return q.removeAll(c);} 5557 public boolean retainAll(Collection<?> c) {return q.retainAll(c);} 5558 // We use inherited addAll; forwarding addAll would be wrong 5559 5560 // Override default methods in Collection 5561 @Override 5562 public void forEach(Consumer<? super E> action) {q.forEach(action);} 5563 @Override 5564 public boolean removeIf(Predicate<? super E> filter) { 5565 return q.removeIf(filter); 5566 } 5567 @Override 5568 public Spliterator<E> spliterator() {return q.spliterator();} 5569 @Override 5570 public Stream<E> stream() {return q.stream();} 5571 @Override 5572 public Stream<E> parallelStream() {return q.parallelStream();} 5573 } 5574 }