1 /* 2 * Copyright (c) 1997, 2013, 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 28 import java.util.function.Consumer; 29 import java.util.function.BiConsumer; 30 import java.util.function.BiFunction; 31 import java.io.IOException; 32 33 // Android-added: Note about spliterator order b/33945212 in Android N 34 /** 35 * <p>Hash table and linked list implementation of the <tt>Map</tt> interface, 36 * with predictable iteration order. This implementation differs from 37 * <tt>HashMap</tt> in that it maintains a doubly-linked list running through 38 * all of its entries. This linked list defines the iteration ordering, 39 * which is normally the order in which keys were inserted into the map 40 * (<i>insertion-order</i>). Note that insertion order is not affected 41 * if a key is <i>re-inserted</i> into the map. (A key <tt>k</tt> is 42 * reinserted into a map <tt>m</tt> if <tt>m.put(k, v)</tt> is invoked when 43 * <tt>m.containsKey(k)</tt> would return <tt>true</tt> immediately prior to 44 * the invocation.) 45 * 46 * <p>This implementation spares its clients from the unspecified, generally 47 * chaotic ordering provided by {@link HashMap} (and {@link Hashtable}), 48 * without incurring the increased cost associated with {@link TreeMap}. It 49 * can be used to produce a copy of a map that has the same order as the 50 * original, regardless of the original map's implementation: 51 * <pre> 52 * void foo(Map m) { 53 * Map copy = new LinkedHashMap(m); 54 * ... 55 * } 56 * </pre> 57 * This technique is particularly useful if a module takes a map on input, 58 * copies it, and later returns results whose order is determined by that of 59 * the copy. (Clients generally appreciate having things returned in the same 60 * order they were presented.) 61 * 62 * <p>A special {@link #LinkedHashMap(int,float,boolean) constructor} is 63 * provided to create a linked hash map whose order of iteration is the order 64 * in which its entries were last accessed, from least-recently accessed to 65 * most-recently (<i>access-order</i>). This kind of map is well-suited to 66 * building LRU caches. Invoking the {@code put}, {@code putIfAbsent}, 67 * {@code get}, {@code getOrDefault}, {@code compute}, {@code computeIfAbsent}, 68 * {@code computeIfPresent}, or {@code merge} methods results 69 * in an access to the corresponding entry (assuming it exists after the 70 * invocation completes). The {@code replace} methods only result in an access 71 * of the entry if the value is replaced. The {@code putAll} method generates one 72 * entry access for each mapping in the specified map, in the order that 73 * key-value mappings are provided by the specified map's entry set iterator. 74 * <i>No other methods generate entry accesses.</i> In particular, operations 75 * on collection-views do <i>not</i> affect the order of iteration of the 76 * backing map. 77 * 78 * <p>The {@link #removeEldestEntry(Map.Entry)} method may be overridden to 79 * impose a policy for removing stale mappings automatically when new mappings 80 * are added to the map. 81 * 82 * <p>This class provides all of the optional <tt>Map</tt> operations, and 83 * permits null elements. Like <tt>HashMap</tt>, it provides constant-time 84 * performance for the basic operations (<tt>add</tt>, <tt>contains</tt> and 85 * <tt>remove</tt>), assuming the hash function disperses elements 86 * properly among the buckets. Performance is likely to be just slightly 87 * below that of <tt>HashMap</tt>, due to the added expense of maintaining the 88 * linked list, with one exception: Iteration over the collection-views 89 * of a <tt>LinkedHashMap</tt> requires time proportional to the <i>size</i> 90 * of the map, regardless of its capacity. Iteration over a <tt>HashMap</tt> 91 * is likely to be more expensive, requiring time proportional to its 92 * <i>capacity</i>. 93 * 94 * <p>A linked hash map has two parameters that affect its performance: 95 * <i>initial capacity</i> and <i>load factor</i>. They are defined precisely 96 * as for <tt>HashMap</tt>. Note, however, that the penalty for choosing an 97 * excessively high value for initial capacity is less severe for this class 98 * than for <tt>HashMap</tt>, as iteration times for this class are unaffected 99 * by capacity. 100 * 101 * <p><strong>Note that this implementation is not synchronized.</strong> 102 * If multiple threads access a linked hash map concurrently, and at least 103 * one of the threads modifies the map structurally, it <em>must</em> be 104 * synchronized externally. This is typically accomplished by 105 * synchronizing on some object that naturally encapsulates the map. 106 * 107 * If no such object exists, the map should be "wrapped" using the 108 * {@link Collections#synchronizedMap Collections.synchronizedMap} 109 * method. This is best done at creation time, to prevent accidental 110 * unsynchronized access to the map:<pre> 111 * Map m = Collections.synchronizedMap(new LinkedHashMap(...));</pre> 112 * 113 * A structural modification is any operation that adds or deletes one or more 114 * mappings or, in the case of access-ordered linked hash maps, affects 115 * iteration order. In insertion-ordered linked hash maps, merely changing 116 * the value associated with a key that is already contained in the map is not 117 * a structural modification. <strong>In access-ordered linked hash maps, 118 * merely querying the map with <tt>get</tt> is a structural modification. 119 * </strong>) 120 * 121 * <p>The iterators returned by the <tt>iterator</tt> method of the collections 122 * returned by all of this class's collection view methods are 123 * <em>fail-fast</em>: if the map is structurally modified at any time after 124 * the iterator is created, in any way except through the iterator's own 125 * <tt>remove</tt> method, the iterator will throw a {@link 126 * ConcurrentModificationException}. Thus, in the face of concurrent 127 * modification, the iterator fails quickly and cleanly, rather than risking 128 * arbitrary, non-deterministic behavior at an undetermined time in the future. 129 * 130 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed 131 * as it is, generally speaking, impossible to make any hard guarantees in the 132 * presence of unsynchronized concurrent modification. Fail-fast iterators 133 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis. 134 * Therefore, it would be wrong to write a program that depended on this 135 * exception for its correctness: <i>the fail-fast behavior of iterators 136 * should be used only to detect bugs.</i> 137 * 138 * <p>The spliterators returned by the spliterator method of the collections 139 * returned by all of this class's collection view methods are 140 * <em><a href="Spliterator.html#binding">late-binding</a></em>, 141 * <em>fail-fast</em>, and additionally report {@link Spliterator#ORDERED}. 142 * <em>Note</em>: The implementation of these spliterators in Android Nougat 143 * (API levels 24 and 25) uses the wrong order (inconsistent with the 144 * iterators, which use the correct order), despite reporting 145 * {@link Spliterator#ORDERED}. You may use the following code fragments 146 * to obtain a correctly ordered Spliterator on API level 24 and 25: 147 * <ul> 148 * <li>For a Collection view {@code c = lhm.keySet()}, 149 * {@code c = lhm.keySet()} or {@code c = lhm.values()}, use 150 * {@code java.util.Spliterators.spliterator(c, c.spliterator().characteristics())} 151 * instead of {@code c.spliterator()}. 152 * <li>Instead of {@code lhm.stream()} or {@code lhm.parallelStream()}, use 153 * {@code java.util.stream.StreamSupport.stream(spliterator, false)} 154 * to construct a (nonparallel) {@link java.util.stream.Stream} from 155 * such a {@code Spliterator}. 156 * </ul> 157 * Note that these workarounds are only suggested where {@code lhm} is a 158 * {@code LinkedHashMap}. 159 * 160 * <p>This class is a member of the 161 * <a href="{@docRoot}/../technotes/guides/collections/index.html"> 162 * Java Collections Framework</a>. 163 * 164 * @implNote 165 * The spliterators returned by the spliterator method of the collections 166 * returned by all of this class's collection view methods are created from 167 * the iterators of the corresponding collections. 168 * 169 * @param <K> the type of keys maintained by this map 170 * @param <V> the type of mapped values 171 * 172 * @author Josh Bloch 173 * @see Object#hashCode() 174 * @see Collection 175 * @see Map 176 * @see HashMap 177 * @see TreeMap 178 * @see Hashtable 179 * @since 1.4 180 */ 181 public class LinkedHashMap<K,V> 182 extends HashMap<K,V> 183 implements Map<K,V> 184 { 185 186 /* 187 * Implementation note. A previous version of this class was 188 * internally structured a little differently. Because superclass 189 * HashMap now uses trees for some of its nodes, class 190 * LinkedHashMap.Entry is now treated as intermediary node class 191 * that can also be converted to tree form. 192 * 193 * BEGIN Android-changed 194 * LinkedHashMapEntry should not be renamed. Specifically, for 195 * source compatibility with earlier versions of Android, this 196 * nested class must not be named "Entry". Otherwise, it would 197 * hide Map.Entry which would break compilation of code like: 198 * 199 * LinkedHashMap.Entry<K, V> entry = map.entrySet().iterator.next() 200 * 201 * To compile, that code snippet's "LinkedHashMap.Entry" must 202 * mean java.util.Map.Entry which is the compile time type of 203 * entrySet()'s elements. 204 * END Android-changed 205 * 206 * The changes in node classes also require using two fields 207 * (head, tail) rather than a pointer to a header node to maintain 208 * the doubly-linked before/after list. This class also 209 * previously used a different style of callback methods upon 210 * access, insertion, and removal. 211 */ 212 213 /** 214 * HashMap.Node subclass for normal LinkedHashMap entries. 215 */ 216 static class LinkedHashMapEntry<K,V> extends HashMap.Node<K,V> { 217 LinkedHashMapEntry<K,V> before, after; LinkedHashMapEntry(int hash, K key, V value, Node<K,V> next)218 LinkedHashMapEntry(int hash, K key, V value, Node<K,V> next) { 219 super(hash, key, value, next); 220 } 221 } 222 223 private static final long serialVersionUID = 3801124242820219131L; 224 225 /** 226 * The head (eldest) of the doubly linked list. 227 */ 228 transient LinkedHashMapEntry<K,V> head; 229 230 /** 231 * The tail (youngest) of the doubly linked list. 232 */ 233 transient LinkedHashMapEntry<K,V> tail; 234 235 /** 236 * The iteration ordering method for this linked hash map: <tt>true</tt> 237 * for access-order, <tt>false</tt> for insertion-order. 238 * 239 * @serial 240 */ 241 final boolean accessOrder; 242 243 // internal utilities 244 245 // link at the end of list linkNodeLast(LinkedHashMapEntry<K,V> p)246 private void linkNodeLast(LinkedHashMapEntry<K,V> p) { 247 LinkedHashMapEntry<K,V> last = tail; 248 tail = p; 249 if (last == null) 250 head = p; 251 else { 252 p.before = last; 253 last.after = p; 254 } 255 } 256 257 // apply src's links to dst transferLinks(LinkedHashMapEntry<K,V> src, LinkedHashMapEntry<K,V> dst)258 private void transferLinks(LinkedHashMapEntry<K,V> src, 259 LinkedHashMapEntry<K,V> dst) { 260 LinkedHashMapEntry<K,V> b = dst.before = src.before; 261 LinkedHashMapEntry<K,V> a = dst.after = src.after; 262 if (b == null) 263 head = dst; 264 else 265 b.after = dst; 266 if (a == null) 267 tail = dst; 268 else 269 a.before = dst; 270 } 271 272 // overrides of HashMap hook methods 273 reinitialize()274 void reinitialize() { 275 super.reinitialize(); 276 head = tail = null; 277 } 278 newNode(int hash, K key, V value, Node<K,V> e)279 Node<K,V> newNode(int hash, K key, V value, Node<K,V> e) { 280 LinkedHashMapEntry<K,V> p = 281 new LinkedHashMapEntry<K,V>(hash, key, value, e); 282 linkNodeLast(p); 283 return p; 284 } 285 replacementNode(Node<K,V> p, Node<K,V> next)286 Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) { 287 LinkedHashMapEntry<K,V> q = (LinkedHashMapEntry<K,V>)p; 288 LinkedHashMapEntry<K,V> t = 289 new LinkedHashMapEntry<K,V>(q.hash, q.key, q.value, next); 290 transferLinks(q, t); 291 return t; 292 } 293 newTreeNode(int hash, K key, V value, Node<K,V> next)294 TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) { 295 TreeNode<K,V> p = new TreeNode<K,V>(hash, key, value, next); 296 linkNodeLast(p); 297 return p; 298 } 299 replacementTreeNode(Node<K,V> p, Node<K,V> next)300 TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) { 301 LinkedHashMapEntry<K,V> q = (LinkedHashMapEntry<K,V>)p; 302 TreeNode<K,V> t = new TreeNode<K,V>(q.hash, q.key, q.value, next); 303 transferLinks(q, t); 304 return t; 305 } 306 afterNodeRemoval(Node<K,V> e)307 void afterNodeRemoval(Node<K,V> e) { // unlink 308 LinkedHashMapEntry<K,V> p = 309 (LinkedHashMapEntry<K,V>)e, b = p.before, a = p.after; 310 p.before = p.after = null; 311 if (b == null) 312 head = a; 313 else 314 b.after = a; 315 if (a == null) 316 tail = b; 317 else 318 a.before = b; 319 } 320 afterNodeInsertion(boolean evict)321 void afterNodeInsertion(boolean evict) { // possibly remove eldest 322 LinkedHashMapEntry<K,V> first; 323 if (evict && (first = head) != null && removeEldestEntry(first)) { 324 K key = first.key; 325 removeNode(hash(key), key, null, false, true); 326 } 327 } 328 afterNodeAccess(Node<K,V> e)329 void afterNodeAccess(Node<K,V> e) { // move node to last 330 LinkedHashMapEntry<K,V> last; 331 if (accessOrder && (last = tail) != e) { 332 LinkedHashMapEntry<K,V> p = 333 (LinkedHashMapEntry<K,V>)e, b = p.before, a = p.after; 334 p.after = null; 335 if (b == null) 336 head = a; 337 else 338 b.after = a; 339 if (a != null) 340 a.before = b; 341 else 342 last = b; 343 if (last == null) 344 head = p; 345 else { 346 p.before = last; 347 last.after = p; 348 } 349 tail = p; 350 ++modCount; 351 } 352 } 353 internalWriteEntries(java.io.ObjectOutputStream s)354 void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException { 355 for (LinkedHashMapEntry<K,V> e = head; e != null; e = e.after) { 356 s.writeObject(e.key); 357 s.writeObject(e.value); 358 } 359 } 360 361 /** 362 * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance 363 * with the specified initial capacity and load factor. 364 * 365 * @param initialCapacity the initial capacity 366 * @param loadFactor the load factor 367 * @throws IllegalArgumentException if the initial capacity is negative 368 * or the load factor is nonpositive 369 */ LinkedHashMap(int initialCapacity, float loadFactor)370 public LinkedHashMap(int initialCapacity, float loadFactor) { 371 super(initialCapacity, loadFactor); 372 accessOrder = false; 373 } 374 375 /** 376 * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance 377 * with the specified initial capacity and a default load factor (0.75). 378 * 379 * @param initialCapacity the initial capacity 380 * @throws IllegalArgumentException if the initial capacity is negative 381 */ LinkedHashMap(int initialCapacity)382 public LinkedHashMap(int initialCapacity) { 383 super(initialCapacity); 384 accessOrder = false; 385 } 386 387 /** 388 * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance 389 * with the default initial capacity (16) and load factor (0.75). 390 */ LinkedHashMap()391 public LinkedHashMap() { 392 super(); 393 accessOrder = false; 394 } 395 396 /** 397 * Constructs an insertion-ordered <tt>LinkedHashMap</tt> instance with 398 * the same mappings as the specified map. The <tt>LinkedHashMap</tt> 399 * instance is created with a default load factor (0.75) and an initial 400 * capacity sufficient to hold the mappings in the specified map. 401 * 402 * @param m the map whose mappings are to be placed in this map 403 * @throws NullPointerException if the specified map is null 404 */ LinkedHashMap(Map<? extends K, ? extends V> m)405 public LinkedHashMap(Map<? extends K, ? extends V> m) { 406 super(); 407 accessOrder = false; 408 putMapEntries(m, false); 409 } 410 411 /** 412 * Constructs an empty <tt>LinkedHashMap</tt> instance with the 413 * specified initial capacity, load factor and ordering mode. 414 * 415 * @param initialCapacity the initial capacity 416 * @param loadFactor the load factor 417 * @param accessOrder the ordering mode - <tt>true</tt> for 418 * access-order, <tt>false</tt> for insertion-order 419 * @throws IllegalArgumentException if the initial capacity is negative 420 * or the load factor is nonpositive 421 */ LinkedHashMap(int initialCapacity, float loadFactor, boolean accessOrder)422 public LinkedHashMap(int initialCapacity, 423 float loadFactor, 424 boolean accessOrder) { 425 super(initialCapacity, loadFactor); 426 this.accessOrder = accessOrder; 427 } 428 429 430 /** 431 * Returns <tt>true</tt> if this map maps one or more keys to the 432 * specified value. 433 * 434 * @param value value whose presence in this map is to be tested 435 * @return <tt>true</tt> if this map maps one or more keys to the 436 * specified value 437 */ containsValue(Object value)438 public boolean containsValue(Object value) { 439 for (LinkedHashMapEntry<K,V> e = head; e != null; e = e.after) { 440 V v = e.value; 441 if (v == value || (value != null && value.equals(v))) 442 return true; 443 } 444 return false; 445 } 446 447 /** 448 * Returns the value to which the specified key is mapped, 449 * or {@code null} if this map contains no mapping for the key. 450 * 451 * <p>More formally, if this map contains a mapping from a key 452 * {@code k} to a value {@code v} such that {@code (key==null ? k==null : 453 * key.equals(k))}, then this method returns {@code v}; otherwise 454 * it returns {@code null}. (There can be at most one such mapping.) 455 * 456 * <p>A return value of {@code null} does not <i>necessarily</i> 457 * indicate that the map contains no mapping for the key; it's also 458 * possible that the map explicitly maps the key to {@code null}. 459 * The {@link #containsKey containsKey} operation may be used to 460 * distinguish these two cases. 461 */ get(Object key)462 public V get(Object key) { 463 Node<K,V> e; 464 if ((e = getNode(hash(key), key)) == null) 465 return null; 466 if (accessOrder) 467 afterNodeAccess(e); 468 return e.value; 469 } 470 471 /** 472 * {@inheritDoc} 473 */ getOrDefault(Object key, V defaultValue)474 public V getOrDefault(Object key, V defaultValue) { 475 Node<K,V> e; 476 if ((e = getNode(hash(key), key)) == null) 477 return defaultValue; 478 if (accessOrder) 479 afterNodeAccess(e); 480 return e.value; 481 } 482 483 /** 484 * {@inheritDoc} 485 */ clear()486 public void clear() { 487 super.clear(); 488 head = tail = null; 489 } 490 491 // Android-added: eldest(), for internal use in LRU caches 492 /** 493 * Returns the eldest entry in the map, or {@code null} if the map is empty. 494 * @hide 495 */ eldest()496 public Map.Entry<K, V> eldest() { 497 return head; 498 } 499 500 /** 501 * Returns <tt>true</tt> if this map should remove its eldest entry. 502 * This method is invoked by <tt>put</tt> and <tt>putAll</tt> after 503 * inserting a new entry into the map. It provides the implementor 504 * with the opportunity to remove the eldest entry each time a new one 505 * is added. This is useful if the map represents a cache: it allows 506 * the map to reduce memory consumption by deleting stale entries. 507 * 508 * <p>Sample use: this override will allow the map to grow up to 100 509 * entries and then delete the eldest entry each time a new entry is 510 * added, maintaining a steady state of 100 entries. 511 * <pre> 512 * private static final int MAX_ENTRIES = 100; 513 * 514 * protected boolean removeEldestEntry(Map.Entry eldest) { 515 * return size() > MAX_ENTRIES; 516 * } 517 * </pre> 518 * 519 * <p>This method typically does not modify the map in any way, 520 * instead allowing the map to modify itself as directed by its 521 * return value. It <i>is</i> permitted for this method to modify 522 * the map directly, but if it does so, it <i>must</i> return 523 * <tt>false</tt> (indicating that the map should not attempt any 524 * further modification). The effects of returning <tt>true</tt> 525 * after modifying the map from within this method are unspecified. 526 * 527 * <p>This implementation merely returns <tt>false</tt> (so that this 528 * map acts like a normal map - the eldest element is never removed). 529 * 530 * @param eldest The least recently inserted entry in the map, or if 531 * this is an access-ordered map, the least recently accessed 532 * entry. This is the entry that will be removed it this 533 * method returns <tt>true</tt>. If the map was empty prior 534 * to the <tt>put</tt> or <tt>putAll</tt> invocation resulting 535 * in this invocation, this will be the entry that was just 536 * inserted; in other words, if the map contains a single 537 * entry, the eldest entry is also the newest. 538 * @return <tt>true</tt> if the eldest entry should be removed 539 * from the map; <tt>false</tt> if it should be retained. 540 */ removeEldestEntry(Map.Entry<K,V> eldest)541 protected boolean removeEldestEntry(Map.Entry<K,V> eldest) { 542 return false; 543 } 544 545 /** 546 * Returns a {@link Set} view of the keys contained in this map. 547 * The set is backed by the map, so changes to the map are 548 * reflected in the set, and vice-versa. If the map is modified 549 * while an iteration over the set is in progress (except through 550 * the iterator's own <tt>remove</tt> operation), the results of 551 * the iteration are undefined. The set supports element removal, 552 * which removes the corresponding mapping from the map, via the 553 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, 554 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> 555 * operations. It does not support the <tt>add</tt> or <tt>addAll</tt> 556 * operations. 557 * Its {@link Spliterator} typically provides faster sequential 558 * performance but much poorer parallel performance than that of 559 * {@code HashMap}. 560 * 561 * @return a set view of the keys contained in this map 562 */ keySet()563 public Set<K> keySet() { 564 Set<K> ks = keySet; 565 if (ks == null) { 566 ks = new LinkedKeySet(); 567 keySet = ks; 568 } 569 return ks; 570 } 571 572 final class LinkedKeySet extends AbstractSet<K> { size()573 public final int size() { return size; } clear()574 public final void clear() { LinkedHashMap.this.clear(); } iterator()575 public final Iterator<K> iterator() { 576 return new LinkedKeyIterator(); 577 } contains(Object o)578 public final boolean contains(Object o) { return containsKey(o); } remove(Object key)579 public final boolean remove(Object key) { 580 return removeNode(hash(key), key, null, false, true) != null; 581 } spliterator()582 public final Spliterator<K> spliterator() { 583 return Spliterators.spliterator(this, Spliterator.SIZED | 584 Spliterator.ORDERED | 585 Spliterator.DISTINCT); 586 } forEach(Consumer<? super K> action)587 public final void forEach(Consumer<? super K> action) { 588 if (action == null) 589 throw new NullPointerException(); 590 int mc = modCount; 591 // Android-changed: Detect changes to modCount early. 592 for (LinkedHashMapEntry<K,V> e = head; (e != null && modCount == mc); e = e.after) 593 action.accept(e.key); 594 if (modCount != mc) 595 throw new ConcurrentModificationException(); 596 } 597 } 598 599 /** 600 * Returns a {@link Collection} view of the values contained in this map. 601 * The collection is backed by the map, so changes to the map are 602 * reflected in the collection, and vice-versa. If the map is 603 * modified while an iteration over the collection is in progress 604 * (except through the iterator's own <tt>remove</tt> operation), 605 * the results of the iteration are undefined. The collection 606 * supports element removal, which removes the corresponding 607 * mapping from the map, via the <tt>Iterator.remove</tt>, 608 * <tt>Collection.remove</tt>, <tt>removeAll</tt>, 609 * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not 610 * support the <tt>add</tt> or <tt>addAll</tt> operations. 611 * Its {@link Spliterator} typically provides faster sequential 612 * performance but much poorer parallel performance than that of 613 * {@code HashMap}. 614 * 615 * @return a view of the values contained in this map 616 */ values()617 public Collection<V> values() { 618 Collection<V> vs = values; 619 if (vs == null) { 620 vs = new LinkedValues(); 621 values = vs; 622 } 623 return vs; 624 } 625 626 final class LinkedValues extends AbstractCollection<V> { size()627 public final int size() { return size; } clear()628 public final void clear() { LinkedHashMap.this.clear(); } iterator()629 public final Iterator<V> iterator() { 630 return new LinkedValueIterator(); 631 } contains(Object o)632 public final boolean contains(Object o) { return containsValue(o); } spliterator()633 public final Spliterator<V> spliterator() { 634 return Spliterators.spliterator(this, Spliterator.SIZED | 635 Spliterator.ORDERED); 636 } forEach(Consumer<? super V> action)637 public final void forEach(Consumer<? super V> action) { 638 if (action == null) 639 throw new NullPointerException(); 640 int mc = modCount; 641 // Android-changed: Detect changes to modCount early. 642 for (LinkedHashMapEntry<K,V> e = head; (e != null && modCount == mc); e = e.after) 643 action.accept(e.value); 644 if (modCount != mc) 645 throw new ConcurrentModificationException(); 646 } 647 } 648 649 /** 650 * Returns a {@link Set} view of the mappings contained in this map. 651 * The set is backed by the map, so changes to the map are 652 * reflected in the set, and vice-versa. If the map is modified 653 * while an iteration over the set is in progress (except through 654 * the iterator's own <tt>remove</tt> operation, or through the 655 * <tt>setValue</tt> operation on a map entry returned by the 656 * iterator) the results of the iteration are undefined. The set 657 * supports element removal, which removes the corresponding 658 * mapping from the map, via the <tt>Iterator.remove</tt>, 659 * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and 660 * <tt>clear</tt> operations. It does not support the 661 * <tt>add</tt> or <tt>addAll</tt> operations. 662 * Its {@link Spliterator} typically provides faster sequential 663 * performance but much poorer parallel performance than that of 664 * {@code HashMap}. 665 * 666 * @return a set view of the mappings contained in this map 667 */ entrySet()668 public Set<Map.Entry<K,V>> entrySet() { 669 Set<Map.Entry<K,V>> es; 670 return (es = entrySet) == null ? (entrySet = new LinkedEntrySet()) : es; 671 } 672 673 final class LinkedEntrySet extends AbstractSet<Map.Entry<K,V>> { size()674 public final int size() { return size; } clear()675 public final void clear() { LinkedHashMap.this.clear(); } iterator()676 public final Iterator<Map.Entry<K,V>> iterator() { 677 return new LinkedEntryIterator(); 678 } contains(Object o)679 public final boolean contains(Object o) { 680 if (!(o instanceof Map.Entry)) 681 return false; 682 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 683 Object key = e.getKey(); 684 Node<K,V> candidate = getNode(hash(key), key); 685 return candidate != null && candidate.equals(e); 686 } remove(Object o)687 public final boolean remove(Object o) { 688 if (o instanceof Map.Entry) { 689 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 690 Object key = e.getKey(); 691 Object value = e.getValue(); 692 return removeNode(hash(key), key, value, true, true) != null; 693 } 694 return false; 695 } spliterator()696 public final Spliterator<Map.Entry<K,V>> spliterator() { 697 return Spliterators.spliterator(this, Spliterator.SIZED | 698 Spliterator.ORDERED | 699 Spliterator.DISTINCT); 700 } forEach(Consumer<? super Map.Entry<K,V>> action)701 public final void forEach(Consumer<? super Map.Entry<K,V>> action) { 702 if (action == null) 703 throw new NullPointerException(); 704 int mc = modCount; 705 // Android-changed: Detect changes to modCount early. 706 for (LinkedHashMapEntry<K,V> e = head; (e != null && mc == modCount); e = e.after) 707 action.accept(e); 708 if (modCount != mc) 709 throw new ConcurrentModificationException(); 710 } 711 } 712 713 // Map overrides 714 forEach(BiConsumer<? super K, ? super V> action)715 public void forEach(BiConsumer<? super K, ? super V> action) { 716 if (action == null) 717 throw new NullPointerException(); 718 int mc = modCount; 719 // Android-changed: Detect changes to modCount early. 720 for (LinkedHashMapEntry<K,V> e = head; modCount == mc && e != null; e = e.after) 721 action.accept(e.key, e.value); 722 if (modCount != mc) 723 throw new ConcurrentModificationException(); 724 } 725 replaceAll(BiFunction<? super K, ? super V, ? extends V> function)726 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 727 if (function == null) 728 throw new NullPointerException(); 729 int mc = modCount; 730 // Android-changed: Detect changes to modCount early. 731 for (LinkedHashMapEntry<K,V> e = head; modCount == mc && e != null; e = e.after) 732 e.value = function.apply(e.key, e.value); 733 if (modCount != mc) 734 throw new ConcurrentModificationException(); 735 } 736 737 // Iterators 738 739 abstract class LinkedHashIterator { 740 LinkedHashMapEntry<K,V> next; 741 LinkedHashMapEntry<K,V> current; 742 int expectedModCount; 743 LinkedHashIterator()744 LinkedHashIterator() { 745 next = head; 746 expectedModCount = modCount; 747 current = null; 748 } 749 hasNext()750 public final boolean hasNext() { 751 return next != null; 752 } 753 nextNode()754 final LinkedHashMapEntry<K,V> nextNode() { 755 LinkedHashMapEntry<K,V> e = next; 756 if (modCount != expectedModCount) 757 throw new ConcurrentModificationException(); 758 if (e == null) 759 throw new NoSuchElementException(); 760 current = e; 761 next = e.after; 762 return e; 763 } 764 remove()765 public final void remove() { 766 Node<K,V> p = current; 767 if (p == null) 768 throw new IllegalStateException(); 769 if (modCount != expectedModCount) 770 throw new ConcurrentModificationException(); 771 current = null; 772 K key = p.key; 773 removeNode(hash(key), key, null, false, false); 774 expectedModCount = modCount; 775 } 776 } 777 778 final class LinkedKeyIterator extends LinkedHashIterator 779 implements Iterator<K> { next()780 public final K next() { return nextNode().getKey(); } 781 } 782 783 final class LinkedValueIterator extends LinkedHashIterator 784 implements Iterator<V> { next()785 public final V next() { return nextNode().value; } 786 } 787 788 final class LinkedEntryIterator extends LinkedHashIterator 789 implements Iterator<Map.Entry<K,V>> { next()790 public final Map.Entry<K,V> next() { return nextNode(); } 791 } 792 793 794 } 795