1 /*
2 * Copyright (c) 1997, 2010, 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.*;
28
29 /**
30 * Hash table based implementation of the <tt>Map</tt> interface. This
31 * implementation provides all of the optional map operations, and permits
32 * <tt>null</tt> values and the <tt>null</tt> key. (The <tt>HashMap</tt>
33 * class is roughly equivalent to <tt>Hashtable</tt>, except that it is
34 * unsynchronized and permits nulls.) This class makes no guarantees as to
35 * the order of the map; in particular, it does not guarantee that the order
36 * will remain constant over time.
37 *
38 * <p>This implementation provides constant-time performance for the basic
39 * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
40 * disperses the elements properly among the buckets. Iteration over
41 * collection views requires time proportional to the "capacity" of the
42 * <tt>HashMap</tt> instance (the number of buckets) plus its size (the number
43 * of key-value mappings). Thus, it's very important not to set the initial
44 * capacity too high (or the load factor too low) if iteration performance is
45 * important.
46 *
47 * <p>An instance of <tt>HashMap</tt> has two parameters that affect its
48 * performance: <i>initial capacity</i> and <i>load factor</i>. The
49 * <i>capacity</i> is the number of buckets in the hash table, and the initial
50 * capacity is simply the capacity at the time the hash table is created. The
51 * <i>load factor</i> is a measure of how full the hash table is allowed to
52 * get before its capacity is automatically increased. When the number of
53 * entries in the hash table exceeds the product of the load factor and the
54 * current capacity, the hash table is <i>rehashed</i> (that is, internal data
55 * structures are rebuilt) so that the hash table has approximately twice the
56 * number of buckets.
57 *
58 * <p>As a general rule, the default load factor (.75) offers a good tradeoff
59 * between time and space costs. Higher values decrease the space overhead
60 * but increase the lookup cost (reflected in most of the operations of the
61 * <tt>HashMap</tt> class, including <tt>get</tt> and <tt>put</tt>). The
62 * expected number of entries in the map and its load factor should be taken
63 * into account when setting its initial capacity, so as to minimize the
64 * number of rehash operations. If the initial capacity is greater
65 * than the maximum number of entries divided by the load factor, no
66 * rehash operations will ever occur.
67 *
68 * <p>If many mappings are to be stored in a <tt>HashMap</tt> instance,
69 * creating it with a sufficiently large capacity will allow the mappings to
70 * be stored more efficiently than letting it perform automatic rehashing as
71 * needed to grow the table.
72 *
73 * <p><strong>Note that this implementation is not synchronized.</strong>
74 * If multiple threads access a hash map concurrently, and at least one of
75 * the threads modifies the map structurally, it <i>must</i> be
76 * synchronized externally. (A structural modification is any operation
77 * that adds or deletes one or more mappings; merely changing the value
78 * associated with a key that an instance already contains is not a
79 * structural modification.) This is typically accomplished by
80 * synchronizing on some object that naturally encapsulates the map.
81 *
82 * If no such object exists, the map should be "wrapped" using the
83 * {@link Collections#synchronizedMap Collections.synchronizedMap}
84 * method. This is best done at creation time, to prevent accidental
85 * unsynchronized access to the map:<pre>
86 * Map m = Collections.synchronizedMap(new HashMap(...));</pre>
87 *
88 * <p>The iterators returned by all of this class's "collection view methods"
89 * are <i>fail-fast</i>: if the map is structurally modified at any time after
90 * the iterator is created, in any way except through the iterator's own
91 * <tt>remove</tt> method, the iterator will throw a
92 * {@link ConcurrentModificationException}. Thus, in the face of concurrent
93 * modification, the iterator fails quickly and cleanly, rather than risking
94 * arbitrary, non-deterministic behavior at an undetermined time in the
95 * future.
96 *
97 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
98 * as it is, generally speaking, impossible to make any hard guarantees in the
99 * presence of unsynchronized concurrent modification. Fail-fast iterators
100 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
101 * Therefore, it would be wrong to write a program that depended on this
102 * exception for its correctness: <i>the fail-fast behavior of iterators
103 * should be used only to detect bugs.</i>
104 *
105 * <p>This class is a member of the
106 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
107 * Java Collections Framework</a>.
108 *
109 * @param <K> the type of keys maintained by this map
110 * @param <V> the type of mapped values
111 *
112 * @author Doug Lea
113 * @author Josh Bloch
114 * @author Arthur van Hoff
115 * @author Neal Gafter
116 * @see Object#hashCode()
117 * @see Collection
118 * @see Map
119 * @see TreeMap
120 * @see Hashtable
121 * @since 1.2
122 */
123
124 public class HashMap<K,V>
125 extends AbstractMap<K,V>
126 implements Map<K,V>, Cloneable, Serializable
127 {
128
129 /**
130 * The default initial capacity - MUST be a power of two.
131 */
132 static final int DEFAULT_INITIAL_CAPACITY = 16;
133
134 /**
135 * The maximum capacity, used if a higher value is implicitly specified
136 * by either of the constructors with arguments.
137 * MUST be a power of two <= 1<<30.
138 */
139 static final int MAXIMUM_CAPACITY = 1 << 30;
140
141 /**
142 * The load factor used when none specified in constructor.
143 */
144 static final float DEFAULT_LOAD_FACTOR = 0.75f;
145
146 /**
147 * The table, resized as necessary. Length MUST Always be a power of two.
148 */
149 transient Entry<?,?>[] table;
150
151 /**
152 * The number of key-value mappings contained in this map.
153 */
154 transient int size;
155
156 /**
157 * The next size value at which to resize (capacity * load factor).
158 * @serial
159 */
160 int threshold;
161
162 /**
163 * The load factor for the hash table.
164 *
165 * @serial
166 */
167 final float loadFactor;
168
169 /**
170 * The number of times this HashMap has been structurally modified
171 * Structural modifications are those that change the number of mappings in
172 * the HashMap or otherwise modify its internal structure (e.g.,
173 * rehash). This field is used to make iterators on Collection-views of
174 * the HashMap fail-fast. (See ConcurrentModificationException).
175 */
176 transient int modCount;
177
178 private static class Holder {
179 /**
180 *
181 */
182 private static final sun.misc.Unsafe UNSAFE;
183
184 /**
185 * Offset of "final" hashmask field we must set in
186 * readObject() method.
187 */
188 private static final long HASHMASK_OFFSET;
189
190 static {
191 try {
192 UNSAFE = sun.misc.Unsafe.getUnsafe();
193 HASHMASK_OFFSET = UNSAFE.objectFieldOffset(
194 HashMap.class.getDeclaredField("hashMask"));
195 } catch (NoSuchFieldException | SecurityException e) {
196 throw new InternalError("Failed to record hashMask offset", e);
197 }
198 }
199 }
200
201 /**
202 * A random mask value that is used for hashcode values associated with this
203 * instance to make hash collisions harder to find.
204 */
205 transient final int hashMask = sun.misc.Hashing.makeHashMask(this);
206
207 /**
208 * Constructs an empty <tt>HashMap</tt> with the specified initial
209 * capacity and load factor.
210 *
211 * @param initialCapacity the initial capacity
212 * @param loadFactor the load factor
213 * @throws IllegalArgumentException if the initial capacity is negative
214 * or the load factor is nonpositive
215 */
216 public HashMap(int initialCapacity, float loadFactor) {
217 if (initialCapacity < 0)
218 throw new IllegalArgumentException("Illegal initial capacity: " +
219 initialCapacity);
220 if (initialCapacity > MAXIMUM_CAPACITY)
221 initialCapacity = MAXIMUM_CAPACITY;
222 if (loadFactor <= 0 || Float.isNaN(loadFactor))
223 throw new IllegalArgumentException("Illegal load factor: " +
224 loadFactor);
225
226 // Find a power of 2 >= initialCapacity
227 int capacity = 1;
228 while (capacity < initialCapacity)
229 capacity <<= 1;
230
231 this.loadFactor = loadFactor;
232 threshold = (int)Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
233 table = new Entry[capacity];
234 init();
235 }
236
237 /**
238 * Constructs an empty <tt>HashMap</tt> with the specified initial
239 * capacity and the default load factor (0.75).
240 *
241 * @param initialCapacity the initial capacity.
242 * @throws IllegalArgumentException if the initial capacity is negative.
243 */
244 public HashMap(int initialCapacity) {
245 this(initialCapacity, DEFAULT_LOAD_FACTOR);
246 }
247
248 /**
249 * Constructs an empty <tt>HashMap</tt> with the default initial capacity
250 * (16) and the default load factor (0.75).
251 */
252 public HashMap() {
253 this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
254 }
255
256 /**
257 * Constructs a new <tt>HashMap</tt> with the same mappings as the
258 * specified <tt>Map</tt>. The <tt>HashMap</tt> is created with
259 * default load factor (0.75) and an initial capacity sufficient to
260 * hold the mappings in the specified <tt>Map</tt>.
261 *
262 * @param m the map whose mappings are to be placed in this map
263 * @throws NullPointerException if the specified map is null
264 */
265 public HashMap(Map<? extends K, ? extends V> m) {
266 this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
267 DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
268 putAllForCreate(m);
269 }
270
271 // internal utilities
272
273 /**
274 * Initialization hook for subclasses. This method is called
275 * in all constructors and pseudo-constructors (clone, readObject)
276 * after HashMap has been initialized but before any entries have
277 * been inserted. (In the absence of this method, readObject would
278 * require explicit knowledge of subclasses.)
279 */
280 void init() {
281 }
282
283 /**
284 * Retrieve object hash code and applies a supplemental hash function to the
285 * result hash, which defends against poor quality hash functions. This is
286 * critical because HashMap uses power-of-two length hash tables, that
287 * otherwise encounter collisions for hashCodes that do not differ
288 * in lower bits.
289 */
290 final int hash(Object k) {
291 int h = hashMask;
292 if ((0 != h) && (k instanceof String)) {
293 return h ^ ((String)k).hash32();
294 }
295
296 h ^= k.hashCode();
297
298 // This function ensures that hashCodes that differ only by
299 // constant multiples at each bit position have a bounded
300 // number of collisions (approximately 8 at default load factor).
301 h ^= (h >>> 20) ^ (h >>> 12);
302 h ^= (h >>> 7) ^ (h >>> 4);
303
304 return h;
305 }
306
307 /**
308 * Returns index for hash code h.
309 */
310 static int indexFor(int h, int length) {
311 return h & (length-1);
312 }
313
314 /**
315 * Returns the number of key-value mappings in this map.
316 *
317 * @return the number of key-value mappings in this map
318 */
319 public int size() {
320 return size;
321 }
322
323 /**
324 * Returns <tt>true</tt> if this map contains no key-value mappings.
325 *
326 * @return <tt>true</tt> if this map contains no key-value mappings
327 */
328 public boolean isEmpty() {
329 return size == 0;
330 }
331
332 /**
333 * Returns the value to which the specified key is mapped,
334 * or {@code null} if this map contains no mapping for the key.
335 *
336 * <p>More formally, if this map contains a mapping from a key
337 * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
338 * key.equals(k))}, then this method returns {@code v}; otherwise
339 * it returns {@code null}. (There can be at most one such mapping.)
340 *
341 * <p>A return value of {@code null} does not <i>necessarily</i>
342 * indicate that the map contains no mapping for the key; it's also
343 * possible that the map explicitly maps the key to {@code null}.
344 * The {@link #containsKey containsKey} operation may be used to
345 * distinguish these two cases.
346 *
347 * @see #put(Object, Object)
348 */
349 @SuppressWarnings("unchecked")
350 public V get(Object key) {
351 Entry<K,V> entry = getEntry(key);
352
353 return null == entry ? null : entry.getValue();
354 }
355
356 /**
357 * Offloaded version of get() to look up null keys. Null keys map
358 * to index 0. This null case is split out into separate methods
359 * for the sake of performance in the two most commonly used
360 * operations (get and put), but incorporated with conditionals in
361 * others.
362 */
363 private Object getForNullKey() {
364 for (Entry<?,?> e = table[0]; e != null; e = e.next) {
365 if (e.key == null)
366 return e.value;
367 }
368 return null;
369 }
370
371 /**
372 * Returns <tt>true</tt> if this map contains a mapping for the
373 * specified key.
374 *
375 * @param key The key whose presence in this map is to be tested
376 * @return <tt>true</tt> if this map contains a mapping for the specified
377 * key.
378 */
379 public boolean containsKey(Object key) {
380 return getEntry(key) != null;
381 }
382
383 /**
384 * Returns the entry associated with the specified key in the
385 * HashMap. Returns null if the HashMap contains no mapping
386 * for the key.
387 */
388 @SuppressWarnings("unchecked")
389 final Entry<K,V> getEntry(Object key) {
390 int hash = (key == null) ? 0 : hash(key);
391 for (Entry<?,?> e = table[indexFor(hash, table.length)];
392 e != null;
393 e = e.next) {
394 Object k;
395 if (e.hash == hash &&
396 ((k = e.key) == key || (key != null && key.equals(k))))
397 return (Entry<K,V>)e;
398 }
399 return null;
400 }
401
402
403 /**
404 * Associates the specified value with the specified key in this map.
405 * If the map previously contained a mapping for the key, the old
406 * value is replaced.
407 *
408 * @param key key with which the specified value is to be associated
409 * @param value value to be associated with the specified key
410 * @return the previous value associated with <tt>key</tt>, or
411 * <tt>null</tt> if there was no mapping for <tt>key</tt>.
412 * (A <tt>null</tt> return can also indicate that the map
413 * previously associated <tt>null</tt> with <tt>key</tt>.)
414 */
415 public V put(K key, V value) {
416 if (key == null)
417 return putForNullKey(value);
418 int hash = hash(key);
419 int i = indexFor(hash, table.length);
420 @SuppressWarnings("unchecked")
421 Entry<K,V> e = (Entry<K,V>)table[i];
422 for(; e != null; e = e.next) {
423 Object k;
424 if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
425 V oldValue = e.value;
426 e.value = value;
427 e.recordAccess(this);
428 return oldValue;
429 }
430 }
431
432 modCount++;
433 addEntry(hash, key, value, i);
434 return null;
435 }
436
437 /**
438 * Offloaded version of put for null keys
439 */
440 private V putForNullKey(V value) {
441 @SuppressWarnings("unchecked")
442 Entry<K,V> e = (Entry<K,V>)table[0];
443 for(; e != null; e = e.next) {
444 if (e.key == null) {
445 V oldValue = e.value;
446 e.value = value;
447 e.recordAccess(this);
448 return oldValue;
449 }
450 }
451 modCount++;
452 addEntry(0, null, value, 0);
453 return null;
454 }
455
456 /**
457 * This method is used instead of put by constructors and
458 * pseudoconstructors (clone, readObject). It does not resize the table,
459 * check for comodification, etc. It calls createEntry rather than
460 * addEntry.
461 */
462 private void putForCreate(K key, V value) {
463 int hash = null == key ? 0 : hash(key);
464 int i = indexFor(hash, table.length);
465
466 /**
467 * Look for preexisting entry for key. This will never happen for
468 * clone or deserialize. It will only happen for construction if the
469 * input Map is a sorted map whose ordering is inconsistent w/ equals.
470 */
471 for (@SuppressWarnings("unchecked")
472 Entry<?,V> e = (Entry<?,V>)table[i]; e != null; e = e.next) {
473 Object k;
474 if (e.hash == hash &&
475 ((k = e.key) == key || (key != null && key.equals(k)))) {
476 e.value = value;
477 return;
478 }
479 }
480
481 createEntry(hash, key, value, i);
482 }
483
484 private void putAllForCreate(Map<? extends K, ? extends V> m) {
485 for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
486 putForCreate(e.getKey(), e.getValue());
487 }
488
489 /**
490 * Rehashes the contents of this map into a new array with a
491 * larger capacity. This method is called automatically when the
492 * number of keys in this map reaches its threshold.
493 *
494 * If current capacity is MAXIMUM_CAPACITY, this method does not
495 * resize the map, but sets threshold to Integer.MAX_VALUE.
496 * This has the effect of preventing future calls.
497 *
498 * @param newCapacity the new capacity, MUST be a power of two;
499 * must be greater than current capacity unless current
500 * capacity is MAXIMUM_CAPACITY (in which case value
501 * is irrelevant).
502 */
503 void resize(int newCapacity) {
504 Entry<?,?>[] oldTable = table;
505 int oldCapacity = oldTable.length;
506 if (oldCapacity == MAXIMUM_CAPACITY) {
507 threshold = Integer.MAX_VALUE;
508 return;
509 }
510
511 Entry<?,?>[] newTable = new Entry<?,?>[newCapacity];
512 transfer(newTable);
513 table = newTable;
514 threshold = (int)Math.min(newCapacity * loadFactor, MAXIMUM_CAPACITY + 1);
515 }
516
517 /**
518 * Transfers all entries from current table to newTable.
519 */
520 @SuppressWarnings("unchecked")
521 void transfer(Entry<?,?>[] newTable) {
522 Entry<?,?>[] src = table;
523 int newCapacity = newTable.length;
524 for (int j = 0; j < src.length; j++ ) {
525 Entry<K,V> e = (Entry<K,V>) src[j];
526 while(null != e) {
527 Entry<K,V> next = e.next;
528 int i = indexFor(e.hash, newCapacity);
529 e.next = (Entry<K,V>) newTable[i];
530 newTable[i] = e;
531 e = next;
532 }
533 }
534 Arrays.fill(table, null);
535 }
536
537 /**
538 * Copies all of the mappings from the specified map to this map.
539 * These mappings will replace any mappings that this map had for
540 * any of the keys currently in the specified map.
541 *
542 * @param m mappings to be stored in this map
543 * @throws NullPointerException if the specified map is null
544 */
545 public void putAll(Map<? extends K, ? extends V> m) {
546 int numKeysToBeAdded = m.size();
547 if (numKeysToBeAdded == 0)
548 return;
549
550 /*
551 * Expand the map if the map if the number of mappings to be added
552 * is greater than or equal to threshold. This is conservative; the
553 * obvious condition is (m.size() + size) >= threshold, but this
554 * condition could result in a map with twice the appropriate capacity,
555 * if the keys to be added overlap with the keys already in this map.
556 * By using the conservative calculation, we subject ourself
557 * to at most one extra resize.
558 */
559 if (numKeysToBeAdded > threshold) {
560 int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
561 if (targetCapacity > MAXIMUM_CAPACITY)
562 targetCapacity = MAXIMUM_CAPACITY;
563 int newCapacity = table.length;
564 while (newCapacity < targetCapacity)
565 newCapacity <<= 1;
566 if (newCapacity > table.length)
567 resize(newCapacity);
568 }
569
570 for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
571 put(e.getKey(), e.getValue());
572 }
573
574 /**
575 * Removes the mapping for the specified key from this map if present.
576 *
577 * @param key key whose mapping is to be removed from the map
578 * @return the previous value associated with <tt>key</tt>, or
579 * <tt>null</tt> if there was no mapping for <tt>key</tt>.
580 * (A <tt>null</tt> return can also indicate that the map
581 * previously associated <tt>null</tt> with <tt>key</tt>.)
582 */
583 public V remove(Object key) {
584 Entry<K,V> e = removeEntryForKey(key);
585 return (e == null ? null : e.value);
586 }
587
588 /**
589 * Removes and returns the entry associated with the specified key
590 * in the HashMap. Returns null if the HashMap contains no mapping
591 * for this key.
592 */
593 final Entry<K,V> removeEntryForKey(Object key) {
594 int hash = (key == null) ? 0 : hash(key);
595 int i = indexFor(hash, table.length);
596 @SuppressWarnings("unchecked")
597 Entry<K,V> prev = (Entry<K,V>)table[i];
598 Entry<K,V> e = prev;
599
600 while (e != null) {
601 Entry<K,V> next = e.next;
602 Object k;
603 if (e.hash == hash &&
604 ((k = e.key) == key || (key != null && key.equals(k)))) {
605 modCount++;
606 size--;
607 if (prev == e)
608 table[i] = next;
609 else
610 prev.next = next;
611 e.recordRemoval(this);
612 return e;
613 }
614 prev = e;
615 e = next;
616 }
617
618 return e;
619 }
620
621 /**
622 * Special version of remove for EntrySet using {@code Map.Entry.equals()}
623 * for matching.
624 */
625 final Entry<K,V> removeMapping(Object o) {
626 if (!(o instanceof Map.Entry))
627 return null;
628
629 Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
630 Object key = entry.getKey();
631 int hash = (key == null) ? 0 : hash(key.hashCode());
632 int i = indexFor(hash, table.length);
633 @SuppressWarnings("unchecked")
634 Entry<K,V> prev = (Entry<K,V>)table[i];
635 Entry<K,V> e = prev;
636
637 while (e != null) {
638 Entry<K,V> next = e.next;
639 if (e.hash == hash && e.equals(entry)) {
640 modCount++;
641 size--;
642 if (prev == e)
643 table[i] = next;
644 else
645 prev.next = next;
646 e.recordRemoval(this);
647 return e;
648 }
649 prev = e;
650 e = next;
651 }
652
653 return e;
654 }
655
656 /**
657 * Removes all of the mappings from this map.
658 * The map will be empty after this call returns.
659 */
660 public void clear() {
661 modCount++;
662 Entry<?,?>[] tab = table;
663 for (int i = 0; i < tab.length; i++)
664 tab[i] = null;
665 size = 0;
666 }
667
668 /**
669 * Returns <tt>true</tt> if this map maps one or more keys to the
670 * specified value.
671 *
672 * @param value value whose presence in this map is to be tested
673 * @return <tt>true</tt> if this map maps one or more keys to the
674 * specified value
675 */
676 public boolean containsValue(Object value) {
677 if (value == null)
678 return containsNullValue();
679
680 Entry<?,?>[] tab = table;
681 for (int i = 0; i < tab.length ; i++)
682 for (Entry<?,?> e = tab[i] ; e != null ; e = e.next)
683 if (value.equals(e.value))
684 return true;
685 return false;
686 }
687
688 /**
689 * Special-case code for containsValue with null argument
690 */
691 private boolean containsNullValue() {
692 Entry<?,?>[] tab = table;
693 for (int i = 0; i < tab.length ; i++)
694 for (Entry<?,?> e = tab[i] ; e != null ; e = e.next)
695 if (e.value == null)
696 return true;
697 return false;
698 }
699
700 /**
701 * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
702 * values themselves are not cloned.
703 *
704 * @return a shallow copy of this map
705 */
706 @SuppressWarnings("unchecked")
707 public Object clone() {
708 HashMap<K,V> result = null;
709 try {
710 result = (HashMap<K,V>)super.clone();
711 } catch (CloneNotSupportedException e) {
712 // assert false;
713 }
714 result.table = new Entry<?,?>[table.length];
715 result.entrySet = null;
716 result.modCount = 0;
717 result.size = 0;
718 result.init();
719 result.putAllForCreate(this);
720
721 return result;
722 }
723
724 static class Entry<K,V> implements Map.Entry<K,V> {
725 final K key;
726 V value;
727 Entry<K,V> next;
728 final int hash;
729
730 /**
731 * Creates new entry.
732 */
733 Entry(int h, K k, V v, Entry<K,V> n) {
734 value = v;
735 next = n;
736 key = k;
737 hash = h;
738 }
739
740 public final K getKey() {
741 return key;
742 }
743
744 public final V getValue() {
745 return value;
746 }
747
748 public final V setValue(V newValue) {
749 V oldValue = value;
750 value = newValue;
751 return oldValue;
752 }
753
754 public final boolean equals(Object o) {
755 if (!(o instanceof Map.Entry))
756 return false;
757 Map.Entry<?,?> e = (Map.Entry<?,?>)o;
758 Object k1 = getKey();
759 Object k2 = e.getKey();
760 if (k1 == k2 || (k1 != null && k1.equals(k2))) {
761 Object v1 = getValue();
762 Object v2 = e.getValue();
763 if (v1 == v2 || (v1 != null && v1.equals(v2)))
764 return true;
765 }
766 return false;
767 }
768
769 public final int hashCode() {
770 return (key==null ? 0 : key.hashCode()) ^
771 (value==null ? 0 : value.hashCode());
772 }
773
774 public final String toString() {
775 return getKey() + "=" + getValue();
776 }
777
778 /**
779 * This method is invoked whenever the value in an entry is
780 * overwritten by an invocation of put(k,v) for a key k that's already
781 * in the HashMap.
782 */
783 void recordAccess(HashMap<K,V> m) {
784 }
785
786 /**
787 * This method is invoked whenever the entry is
788 * removed from the table.
789 */
790 void recordRemoval(HashMap<K,V> m) {
791 }
792 }
793
794 /**
795 * Adds a new entry with the specified key, value and hash code to
796 * the specified bucket. It is the responsibility of this
797 * method to resize the table if appropriate.
798 *
799 * Subclass overrides this to alter the behavior of put method.
800 */
801 void addEntry(int hash, K key, V value, int bucketIndex) {
802 if ((size >= threshold) && (null != table[bucketIndex])) {
803 resize(2 * table.length);
804 hash = hash(key);
805 bucketIndex = indexFor(hash, table.length);
806 }
807
808 createEntry(hash, key, value, bucketIndex);
809 }
810
811 /**
812 * Like addEntry except that this version is used when creating entries
813 * as part of Map construction or "pseudo-construction" (cloning,
814 * deserialization). This version needn't worry about resizing the table.
815 *
816 * Subclass overrides this to alter the behavior of HashMap(Map),
817 * clone, and readObject.
818 */
819 void createEntry(int hash, K key, V value, int bucketIndex) {
820 @SuppressWarnings("unchecked")
821 Entry<K,V> e = (Entry<K,V>)table[bucketIndex];
822 table[bucketIndex] = new Entry<>(hash, key, value, e);
823 size++;
824 }
825
826 private abstract class HashIterator<E> implements Iterator<E> {
827 Entry<?,?> next; // next entry to return
828 int expectedModCount; // For fast-fail
829 int index; // current slot
830 Entry<?,?> current; // current entry
831
832 HashIterator() {
833 expectedModCount = modCount;
834 if (size > 0) { // advance to first entry
835 Entry<?,?>[] t = table;
836 while (index < t.length && (next = t[index++]) == null)
837 ;
838 }
839 }
840
841 public final boolean hasNext() {
842 return next != null;
843 }
844
845 @SuppressWarnings("unchecked")
846 final Entry<K,V> nextEntry() {
847 if (modCount != expectedModCount)
848 throw new ConcurrentModificationException();
849 Entry<?,?> e = next;
850 if (e == null)
851 throw new NoSuchElementException();
852
853 if ((next = e.next) == null) {
854 Entry<?,?>[] t = table;
855 while (index < t.length && (next = t[index++]) == null)
856 ;
857 }
858 current = e;
859 return (Entry<K,V>)e;
860 }
861
862 public void remove() {
863 if (current == null)
864 throw new IllegalStateException();
865 if (modCount != expectedModCount)
866 throw new ConcurrentModificationException();
867 Object k = current.key;
868 current = null;
869 HashMap.this.removeEntryForKey(k);
870 expectedModCount = modCount;
871 }
872 }
873
874 private final class ValueIterator extends HashIterator<V> {
875 public V next() {
876 return nextEntry().value;
877 }
878 }
879
880 private final class KeyIterator extends HashIterator<K> {
881 public K next() {
882 return nextEntry().getKey();
883 }
884 }
885
886 private final class EntryIterator extends HashIterator<Map.Entry<K,V>> {
887 public Map.Entry<K,V> next() {
888 return nextEntry();
889 }
890 }
891
892 // Subclass overrides these to alter behavior of views' iterator() method
893 Iterator<K> newKeyIterator() {
894 return new KeyIterator();
895 }
896 Iterator<V> newValueIterator() {
897 return new ValueIterator();
898 }
899 Iterator<Map.Entry<K,V>> newEntryIterator() {
900 return new EntryIterator();
901 }
902
903
904 // Views
905
906 private transient Set<Map.Entry<K,V>> entrySet = null;
907
908 /**
909 * Returns a {@link Set} view of the keys contained in this map.
910 * The set is backed by the map, so changes to the map are
911 * reflected in the set, and vice-versa. If the map is modified
912 * while an iteration over the set is in progress (except through
913 * the iterator's own <tt>remove</tt> operation), the results of
914 * the iteration are undefined. The set supports element removal,
915 * which removes the corresponding mapping from the map, via the
916 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
917 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
918 * operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
919 * operations.
920 */
921 public Set<K> keySet() {
922 Set<K> ks = keySet;
923 return (ks != null ? ks : (keySet = new KeySet()));
924 }
925
926 private final class KeySet extends AbstractSet<K> {
927 public Iterator<K> iterator() {
928 return newKeyIterator();
929 }
930 public int size() {
931 return size;
932 }
933 public boolean contains(Object o) {
934 return containsKey(o);
935 }
936 public boolean remove(Object o) {
937 return HashMap.this.removeEntryForKey(o) != null;
938 }
939 public void clear() {
940 HashMap.this.clear();
941 }
942 }
943
944 /**
945 * Returns a {@link Collection} view of the values contained in this map.
946 * The collection is backed by the map, so changes to the map are
947 * reflected in the collection, and vice-versa. If the map is
948 * modified while an iteration over the collection is in progress
949 * (except through the iterator's own <tt>remove</tt> operation),
950 * the results of the iteration are undefined. The collection
951 * supports element removal, which removes the corresponding
952 * mapping from the map, via the <tt>Iterator.remove</tt>,
953 * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
954 * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
955 * support the <tt>add</tt> or <tt>addAll</tt> operations.
956 */
957 public Collection<V> values() {
958 Collection<V> vs = values;
959 return (vs != null ? vs : (values = new Values()));
960 }
961
962 private final class Values extends AbstractCollection<V> {
963 public Iterator<V> iterator() {
964 return newValueIterator();
965 }
966 public int size() {
967 return size;
968 }
969 public boolean contains(Object o) {
970 return containsValue(o);
971 }
972 public void clear() {
973 HashMap.this.clear();
974 }
975 }
976
977 /**
978 * Returns a {@link Set} view of the mappings contained in this map.
979 * The set is backed by the map, so changes to the map are
980 * reflected in the set, and vice-versa. If the map is modified
981 * while an iteration over the set is in progress (except through
982 * the iterator's own <tt>remove</tt> operation, or through the
983 * <tt>setValue</tt> operation on a map entry returned by the
984 * iterator) the results of the iteration are undefined. The set
985 * supports element removal, which removes the corresponding
986 * mapping from the map, via the <tt>Iterator.remove</tt>,
987 * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
988 * <tt>clear</tt> operations. It does not support the
989 * <tt>add</tt> or <tt>addAll</tt> operations.
990 *
991 * @return a set view of the mappings contained in this map
992 */
993 public Set<Map.Entry<K,V>> entrySet() {
994 return entrySet0();
995 }
996
997 private Set<Map.Entry<K,V>> entrySet0() {
998 Set<Map.Entry<K,V>> es = entrySet;
999 return es != null ? es : (entrySet = new EntrySet());
1000 }
1001
1002 private final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
1003 public Iterator<Map.Entry<K,V>> iterator() {
1004 return newEntryIterator();
1005 }
1006 public boolean contains(Object o) {
1007 if (!(o instanceof Map.Entry))
1008 return false;
1009 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
1010 Entry<K,V> candidate = getEntry(e.getKey());
1011 return candidate != null && candidate.equals(e);
1012 }
1013 public boolean remove(Object o) {
1014 return removeMapping(o) != null;
1015 }
1016 public int size() {
1017 return size;
1018 }
1019 public void clear() {
1020 HashMap.this.clear();
1021 }
1022 }
1023
1024 /**
1025 * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
1026 * serialize it).
1027 *
1028 * @serialData The <i>capacity</i> of the HashMap (the length of the
1029 * bucket array) is emitted (int), followed by the
1030 * <i>size</i> (an int, the number of key-value
1031 * mappings), followed by the key (Object) and value (Object)
1032 * for each key-value mapping. The key-value mappings are
1033 * emitted in no particular order.
1034 */
1035 private void writeObject(java.io.ObjectOutputStream s)
1036 throws IOException
1037 {
1038 Iterator<Map.Entry<K,V>> i =
1039 (size > 0) ? entrySet0().iterator() : null;
1040
1041 // Write out the threshold, loadfactor, and any hidden stuff
1042 s.defaultWriteObject();
1043
1044 // Write out number of buckets
1045 s.writeInt(table.length);
1046
1047 // Write out size (number of Mappings)
1048 s.writeInt(size);
1049
1050 // Write out keys and values (alternating)
1051 if (size > 0) {
1052 for(Map.Entry<K,V> e : entrySet0()) {
1053 s.writeObject(e.getKey());
1054 s.writeObject(e.getValue());
1055 }
1056 }
1057 }
1058
1059 private static final long serialVersionUID = 362498820763181265L;
1060
1061 /**
1062 * Reconstitute the {@code HashMap} instance from a stream (i.e.,
1063 * deserialize it).
1064 */
1065 private void readObject(java.io.ObjectInputStream s)
1066 throws IOException, ClassNotFoundException
1067 {
1068 // Read in the threshold (ignored), loadfactor, and any hidden stuff
1069 s.defaultReadObject();
1070 if (loadFactor <= 0 || Float.isNaN(loadFactor))
1071 throw new InvalidObjectException("Illegal load factor: " +
1072 loadFactor);
1073
1074 // set hashMask
1075 Holder.UNSAFE.putIntVolatile(this, Holder.HASHMASK_OFFSET,
1076 sun.misc.Hashing.makeHashMask(this));
1077
1078 // Read in number of buckets and allocate the bucket array;
1079 s.readInt(); // ignored
1080
1081 // Read number of mappings
1082 int mappings = s.readInt();
1083 if (mappings < 0)
1084 throw new InvalidObjectException("Illegal mappings count: " +
1085 mappings);
1086
1087 int initialCapacity = (int) Math.min(
1088 // capacity chosen by number of mappings
1089 // and desired load (if >= 0.25)
1090 mappings * Math.min(1 / loadFactor, 4.0f),
1091 // we have limits...
1092 HashMap.MAXIMUM_CAPACITY);
1093 int capacity = 1;
1094 // find smallest power of two which holds all mappings
1095 while (capacity < initialCapacity) {
1096 capacity <<= 1;
1097 }
1098
1099 table = new Entry[capacity];
1100 threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
1101 init(); // Give subclass a chance to do its thing.
1102
1103
1104 // Read the keys and values, and put the mappings in the HashMap
1105 for (int i=0; i<mappings; i++) {
1106 @SuppressWarnings("unchecked")
1107 K key = (K) s.readObject();
1108 @SuppressWarnings("unchecked")
1109 V value = (V) s.readObject();
1110 putForCreate(key, value);
1111 }
1112 }
1113
1114 // These methods are used when serializing HashSets
1115 int capacity() { return table.length; }
1116 float loadFactor() { return loadFactor; }
1117 }