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.io.IOException;
29 import java.io.InvalidObjectException;
30 import java.io.Serializable;
31 import java.lang.ref.WeakReference;
32 import java.lang.reflect.ParameterizedType;
33 import java.lang.reflect.Type;
34 import java.util.function.BiConsumer;
35 import java.util.function.BiFunction;
36 import java.util.function.Consumer;
37 import java.util.function.Function;
38
39 /**
40 * Hash table based implementation of the <tt>Map</tt> interface. This
41 * implementation provides all of the optional map operations, and permits
42 * <tt>null</tt> values and the <tt>null</tt> key. (The <tt>HashMap</tt>
43 * class is roughly equivalent to <tt>Hashtable</tt>, except that it is
44 * unsynchronized and permits nulls.) This class makes no guarantees as to
45 * the order of the map; in particular, it does not guarantee that the order
46 * will remain constant over time.
47 *
48 * <p>This implementation provides constant-time performance for the basic
49 * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
50 * disperses the elements properly among the buckets. Iteration over
51 * collection views requires time proportional to the "capacity" of the
52 * <tt>HashMap</tt> instance (the number of buckets) plus its size (the number
53 * of key-value mappings). Thus, it's very important not to set the initial
54 * capacity too high (or the load factor too low) if iteration performance is
55 * important.
56 *
57 * <p>An instance of <tt>HashMap</tt> has two parameters that affect its
58 * performance: <i>initial capacity</i> and <i>load factor</i>. The
59 * <i>capacity</i> is the number of buckets in the hash table, and the initial
60 * capacity is simply the capacity at the time the hash table is created. The
61 * <i>load factor</i> is a measure of how full the hash table is allowed to
62 * get before its capacity is automatically increased. When the number of
63 * entries in the hash table exceeds the product of the load factor and the
64 * current capacity, the hash table is <i>rehashed</i> (that is, internal data
65 * structures are rebuilt) so that the hash table has approximately twice the
66 * number of buckets.
67 *
68 * <p>As a general rule, the default load factor (.75) offers a good
69 * tradeoff between time and space costs. Higher values decrease the
70 * space overhead but increase the lookup cost (reflected in most of
71 * the operations of the <tt>HashMap</tt> class, including
72 * <tt>get</tt> and <tt>put</tt>). The expected number of entries in
73 * the map and its load factor should be taken into account when
74 * setting its initial capacity, so as to minimize the number of
75 * rehash operations. If the initial capacity is greater than the
76 * maximum number of entries divided by the load factor, no rehash
77 * operations will ever occur.
78 *
79 * <p>If many mappings are to be stored in a <tt>HashMap</tt>
80 * instance, creating it with a sufficiently large capacity will allow
81 * the mappings to be stored more efficiently than letting it perform
82 * automatic rehashing as needed to grow the table. Note that using
83 * many keys with the same {@code hashCode()} is a sure way to slow
84 * down performance of any hash table. To ameliorate impact, when keys
85 * are {@link Comparable}, this class may use comparison order among
86 * keys to help break ties.
87 *
88 * <p><strong>Note that this implementation is not synchronized.</strong>
89 * If multiple threads access a hash map concurrently, and at least one of
90 * the threads modifies the map structurally, it <i>must</i> be
91 * synchronized externally. (A structural modification is any operation
92 * that adds or deletes one or more mappings; merely changing the value
93 * associated with a key that an instance already contains is not a
94 * structural modification.) This is typically accomplished by
95 * synchronizing on some object that naturally encapsulates the map.
96 *
97 * If no such object exists, the map should be "wrapped" using the
98 * {@link Collections#synchronizedMap Collections.synchronizedMap}
99 * method. This is best done at creation time, to prevent accidental
100 * unsynchronized access to the map:<pre>
101 * Map m = Collections.synchronizedMap(new HashMap(...));</pre>
102 *
103 * <p>The iterators returned by all of this class's "collection view methods"
104 * are <i>fail-fast</i>: if the map is structurally modified at any time after
105 * the iterator is created, in any way except through the iterator's own
106 * <tt>remove</tt> method, the iterator will throw a
107 * {@link ConcurrentModificationException}. Thus, in the face of concurrent
108 * modification, the iterator fails quickly and cleanly, rather than risking
109 * arbitrary, non-deterministic behavior at an undetermined time in the
110 * future.
111 *
112 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
113 * as it is, generally speaking, impossible to make any hard guarantees in the
114 * presence of unsynchronized concurrent modification. Fail-fast iterators
115 * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
116 * Therefore, it would be wrong to write a program that depended on this
117 * exception for its correctness: <i>the fail-fast behavior of iterators
118 * should be used only to detect bugs.</i>
119 *
120 * <p>This class is a member of the
121 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
122 * Java Collections Framework</a>.
123 *
124 * @param <K> the type of keys maintained by this map
125 * @param <V> the type of mapped values
126 *
127 * @author Doug Lea
128 * @author Josh Bloch
129 * @author Arthur van Hoff
130 * @author Neal Gafter
131 * @see Object#hashCode()
132 * @see Collection
133 * @see Map
134 * @see TreeMap
135 * @see Hashtable
136 * @since 1.2
137 */
138 public class HashMap<K,V> extends AbstractMap<K,V>
139 implements Map<K,V>, Cloneable, Serializable {
140
141 private static final long serialVersionUID = 362498820763181265L;
142
143 /*
144 * Implementation notes.
145 *
146 * This map usually acts as a binned (bucketed) hash table, but
147 * when bins get too large, they are transformed into bins of
148 * TreeNodes, each structured similarly to those in
149 * java.util.TreeMap. Most methods try to use normal bins, but
150 * relay to TreeNode methods when applicable (simply by checking
151 * instanceof a node). Bins of TreeNodes may be traversed and
152 * used like any others, but additionally support faster lookup
153 * when overpopulated. However, since the vast majority of bins in
154 * normal use are not overpopulated, checking for existence of
155 * tree bins may be delayed in the course of table methods.
156 *
157 * Tree bins (i.e., bins whose elements are all TreeNodes) are
158 * ordered primarily by hashCode, but in the case of ties, if two
159 * elements are of the same "class C implements Comparable<C>",
160 * type then their compareTo method is used for ordering. (We
161 * conservatively check generic types via reflection to validate
162 * this -- see method comparableClassFor). The added complexity
163 * of tree bins is worthwhile in providing worst-case O(log n)
164 * operations when keys either have distinct hashes or are
165 * orderable, Thus, performance degrades gracefully under
166 * accidental or malicious usages in which hashCode() methods
167 * return values that are poorly distributed, as well as those in
168 * which many keys share a hashCode, so long as they are also
169 * Comparable. (If neither of these apply, we may waste about a
170 * factor of two in time and space compared to taking no
171 * precautions. But the only known cases stem from poor user
172 * programming practices that are already so slow that this makes
173 * little difference.)
174 *
175 * Because TreeNodes are about twice the size of regular nodes, we
176 * use them only when bins contain enough nodes to warrant use
177 * (see TREEIFY_THRESHOLD). And when they become too small (due to
178 * removal or resizing) they are converted back to plain bins. In
179 * usages with well-distributed user hashCodes, tree bins are
180 * rarely used. Ideally, under random hashCodes, the frequency of
181 * nodes in bins follows a Poisson distribution
182 * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
183 * parameter of about 0.5 on average for the default resizing
184 * threshold of 0.75, although with a large variance because of
185 * resizing granularity. Ignoring variance, the expected
186 * occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
187 * factorial(k)). The first values are:
188 *
189 * 0: 0.60653066
190 * 1: 0.30326533
191 * 2: 0.07581633
192 * 3: 0.01263606
193 * 4: 0.00157952
194 * 5: 0.00015795
195 * 6: 0.00001316
196 * 7: 0.00000094
197 * 8: 0.00000006
198 * more: less than 1 in ten million
199 *
200 * The root of a tree bin is normally its first node. However,
201 * sometimes (currently only upon Iterator.remove), the root might
202 * be elsewhere, but can be recovered following parent links
203 * (method TreeNode.root()).
204 *
205 * All applicable internal methods accept a hash code as an
206 * argument (as normally supplied from a public method), allowing
207 * them to call each other without recomputing user hashCodes.
208 * Most internal methods also accept a "tab" argument, that is
209 * normally the current table, but may be a new or old one when
210 * resizing or converting.
211 *
212 * When bin lists are treeified, split, or untreeified, we keep
213 * them in the same relative access/traversal order (i.e., field
214 * Node.next) to better preserve locality, and to slightly
215 * simplify handling of splits and traversals that invoke
216 * iterator.remove. When using comparators on insertion, to keep a
217 * total ordering (or as close as is required here) across
218 * rebalancings, we compare classes and identityHashCodes as
219 * tie-breakers.
220 *
221 * The use and transitions among plain vs tree modes is
222 * complicated by the existence of subclass LinkedHashMap. See
223 * below for hook methods defined to be invoked upon insertion,
224 * removal and access that allow LinkedHashMap internals to
225 * otherwise remain independent of these mechanics. (This also
226 * requires that a map instance be passed to some utility methods
227 * that may create new nodes.)
228 *
229 * The concurrent-programming-like SSA-based coding style helps
230 * avoid aliasing errors amid all of the twisty pointer operations.
231 */
232
233 /**
234 * The default initial capacity - MUST be a power of two.
235 */
236 static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16
237
238 /**
239 * The maximum capacity, used if a higher value is implicitly specified
240 * by either of the constructors with arguments.
241 * MUST be a power of two <= 1<<30.
242 */
243 static final int MAXIMUM_CAPACITY = 1 << 30;
244
245 /**
246 * The load factor used when none specified in constructor.
247 */
248 static final float DEFAULT_LOAD_FACTOR = 0.75f;
249
250 /**
251 * The bin count threshold for using a tree rather than list for a
252 * bin. Bins are converted to trees when adding an element to a
253 * bin with at least this many nodes. The value must be greater
254 * than 2 and should be at least 8 to mesh with assumptions in
255 * tree removal about conversion back to plain bins upon
256 * shrinkage.
257 */
258 static final int TREEIFY_THRESHOLD = 8;
259
260 /**
261 * The bin count threshold for untreeifying a (split) bin during a
262 * resize operation. Should be less than TREEIFY_THRESHOLD, and at
263 * most 6 to mesh with shrinkage detection under removal.
264 */
265 static final int UNTREEIFY_THRESHOLD = 6;
266
267 /**
268 * The smallest table capacity for which bins may be treeified.
269 * (Otherwise the table is resized if too many nodes in a bin.)
270 * Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
271 * between resizing and treeification thresholds.
272 */
273 static final int MIN_TREEIFY_CAPACITY = 64;
274
275 /**
276 * Basic hash bin node, used for most entries. (See below for
277 * TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
278 */
279 static class Node<K,V> implements Map.Entry<K,V> {
280 final int hash;
281 final K key;
282 V value;
283 Node<K,V> next;
284
285 Node(int hash, K key, V value, Node<K,V> next) {
286 this.hash = hash;
287 this.key = key;
288 this.value = value;
289 this.next = next;
290 }
291
292 public final K getKey() { return key; }
293 public final V getValue() { return value; }
294 public final String toString() { return key + "=" + value; }
295
296 public final int hashCode() {
297 return Objects.hashCode(key) ^ Objects.hashCode(value);
298 }
299
300 public final V setValue(V newValue) {
301 V oldValue = value;
302 value = newValue;
303 return oldValue;
304 }
305
306 public final boolean equals(Object o) {
307 if (o == this)
308 return true;
309 if (o instanceof Map.Entry) {
310 Map.Entry<?,?> e = (Map.Entry<?,?>)o;
311 if (Objects.equals(key, e.getKey()) &&
312 Objects.equals(value, e.getValue()))
313 return true;
314 }
315 return false;
316 }
317 }
318
319 /* ---------------- Static utilities -------------- */
320
321 /**
322 * Computes key.hashCode() and spreads (XORs) higher bits of hash
323 * to lower. Because the table uses power-of-two masking, sets of
324 * hashes that vary only in bits above the current mask will
325 * always collide. (Among known examples are sets of Float keys
326 * holding consecutive whole numbers in small tables.) So we
327 * apply a transform that spreads the impact of higher bits
328 * downward. There is a tradeoff between speed, utility, and
329 * quality of bit-spreading. Because many common sets of hashes
330 * are already reasonably distributed (so don't benefit from
331 * spreading), and because we use trees to handle large sets of
332 * collisions in bins, we just XOR some shifted bits in the
333 * cheapest possible way to reduce systematic lossage, as well as
334 * to incorporate impact of the highest bits that would otherwise
335 * never be used in index calculations because of table bounds.
336 */
337 static final int hash(Object key) {
338 int h;
339 return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
340 }
341
342 /** Cache of 1st encountered Class implementing Comparable */
343 private static final class ClassRef extends WeakReference<Class<?>> {
344 final boolean selfComparable;
345
346 ClassRef(Class<?> cc, boolean selfComparable) {
347 super(cc);
348 this.selfComparable = selfComparable;
349 }
350 }
351
352 private transient ClassRef comparableClassRef;
353
354 /**
355 * Returns x's Class if it is of the form "class C implements
356 * Comparable<C>", else null.
357 */
358 Class<?> comparableClassFor(Object x) {
359 if (x instanceof Comparable) {
360 Class<?> c, cc = null;
361 Type[] ts, as;
362 ParameterizedType p;
363 ClassRef ccRef;
364 if ((c = x.getClass()) == String.class) { // bypass checks
365 return c;
366 }
367 if ((ccRef = comparableClassRef) != null &&
368 (cc = ccRef.get()) == c) { // cached
369 return ccRef.selfComparable ? c : null;
370 }
371 if ((ts = c.getGenericInterfaces()) != null) {
372 for (Type t : ts) {
373 if ((t instanceof ParameterizedType) &&
374 ((p = (ParameterizedType) t).getRawType() ==
375 Comparable.class) &&
376 (as = p.getActualTypeArguments()) != null &&
377 as.length == 1 && as[0] == c) { // type arg is c
378 if (cc == null) {
379 // not yet cached or already cleared
380 comparableClassRef = new ClassRef(c, true);
381 }
382 return c;
383 }
384 }
385 }
386 if (cc == null) {
387 // not yet cached or already cleared
388 comparableClassRef = new ClassRef(c, false);
389 }
390 }
391 return null;
392 }
393
394 /**
395 * Returns k.compareTo(x) if x matches kc (k's screened comparable
396 * class), else 0.
397 */
398 @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable
399 static int compareComparables(Class<?> kc, Object k, Object x) {
400 return (x == null || x.getClass() != kc ? 0 :
401 ((Comparable)k).compareTo(x));
402 }
403
404 /**
405 * Returns a power of two size for the given target capacity.
406 */
407 static final int tableSizeFor(int cap) {
408 int n = cap - 1;
409 n |= n >>> 1;
410 n |= n >>> 2;
411 n |= n >>> 4;
412 n |= n >>> 8;
413 n |= n >>> 16;
414 return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
415 }
416
417 /* ---------------- Fields -------------- */
418
419 /**
420 * The table, initialized on first use, and resized as
421 * necessary. When allocated, length is always a power of two.
422 * (We also tolerate length zero in some operations to allow
423 * bootstrapping mechanics that are currently not needed.)
424 */
425 transient Node<K,V>[] table;
426
427 /**
428 * Holds cached entrySet(). Note that AbstractMap fields are used
429 * for keySet() and values().
430 */
431 transient Set<Map.Entry<K,V>> entrySet;
432
433 /**
434 * The number of key-value mappings contained in this map.
435 */
436 transient int size;
437
438 /**
439 * The number of times this HashMap has been structurally modified
440 * Structural modifications are those that change the number of mappings in
441 * the HashMap or otherwise modify its internal structure (e.g.,
442 * rehash). This field is used to make iterators on Collection-views of
443 * the HashMap fail-fast. (See ConcurrentModificationException).
444 */
445 transient int modCount;
446
447 /**
448 * The next size value at which to resize (capacity * load factor).
449 *
450 * @serial
451 */
452 // (The javadoc description is true upon serialization.
453 // Additionally, if the table array has not been allocated, this
454 // field holds the initial array capacity, or zero signifying
455 // DEFAULT_INITIAL_CAPACITY.)
456 int threshold;
457
458 /**
459 * The load factor for the hash table.
460 *
461 * @serial
462 */
463 final float loadFactor;
464
465 /* ---------------- Public operations -------------- */
466
467 /**
468 * Constructs an empty <tt>HashMap</tt> with the specified initial
469 * capacity and load factor.
470 *
471 * @param initialCapacity the initial capacity
472 * @param loadFactor the load factor
473 * @throws IllegalArgumentException if the initial capacity is negative
474 * or the load factor is nonpositive
475 */
476 public HashMap(int initialCapacity, float loadFactor) {
477 if (initialCapacity < 0)
478 throw new IllegalArgumentException("Illegal initial capacity: " +
479 initialCapacity);
480 if (initialCapacity > MAXIMUM_CAPACITY)
481 initialCapacity = MAXIMUM_CAPACITY;
482 if (loadFactor <= 0 || Float.isNaN(loadFactor))
483 throw new IllegalArgumentException("Illegal load factor: " +
484 loadFactor);
485 this.loadFactor = loadFactor;
486 this.threshold = tableSizeFor(initialCapacity);
487 }
488
489 /**
490 * Constructs an empty <tt>HashMap</tt> with the specified initial
491 * capacity and the default load factor (0.75).
492 *
493 * @param initialCapacity the initial capacity.
494 * @throws IllegalArgumentException if the initial capacity is negative.
495 */
496 public HashMap(int initialCapacity) {
497 this(initialCapacity, DEFAULT_LOAD_FACTOR);
498 }
499
500 /**
501 * Constructs an empty <tt>HashMap</tt> with the default initial capacity
502 * (16) and the default load factor (0.75).
503 */
504 public HashMap() {
505 this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
506 }
507
508 /**
509 * Constructs a new <tt>HashMap</tt> with the same mappings as the
510 * specified <tt>Map</tt>. The <tt>HashMap</tt> is created with
511 * default load factor (0.75) and an initial capacity sufficient to
512 * hold the mappings in the specified <tt>Map</tt>.
513 *
514 * @param m the map whose mappings are to be placed in this map
515 * @throws NullPointerException if the specified map is null
516 */
517 public HashMap(Map<? extends K, ? extends V> m) {
518 this.loadFactor = DEFAULT_LOAD_FACTOR;
519 putMapEntries(m, false);
520 }
521
522 /**
523 * Implements Map.putAll and Map constructor
524 *
525 * @param m the map
526 * @param evict false when initially constructing this map, else
527 * true (relayed to method afterNodeInsertion).
528 */
529 final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
530 int s = m.size();
531 if (s > 0) {
532 if (table == null) { // pre-size
533 float ft = ((float)s / loadFactor) + 1.0F;
534 int t = ((ft < (float)MAXIMUM_CAPACITY) ?
535 (int)ft : MAXIMUM_CAPACITY);
536 if (t > threshold)
537 threshold = tableSizeFor(t);
538 }
539 else if (s > threshold)
540 resize();
541 for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
542 K key = e.getKey();
543 V value = e.getValue();
544 putVal(hash(key), key, value, false, evict);
545 }
546 }
547 }
548
549 /**
550 * Returns the number of key-value mappings in this map.
551 *
552 * @return the number of key-value mappings in this map
553 */
554 public int size() {
555 return size;
556 }
557
558 /**
559 * Returns <tt>true</tt> if this map contains no key-value mappings.
560 *
561 * @return <tt>true</tt> if this map contains no key-value mappings
562 */
563 public boolean isEmpty() {
564 return size == 0;
565 }
566
567 /**
568 * Returns the value to which the specified key is mapped,
569 * or {@code null} if this map contains no mapping for the key.
570 *
571 * <p>More formally, if this map contains a mapping from a key
572 * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
573 * key.equals(k))}, then this method returns {@code v}; otherwise
574 * it returns {@code null}. (There can be at most one such mapping.)
575 *
576 * <p>A return value of {@code null} does not <i>necessarily</i>
577 * indicate that the map contains no mapping for the key; it's also
578 * possible that the map explicitly maps the key to {@code null}.
579 * The {@link #containsKey containsKey} operation may be used to
580 * distinguish these two cases.
581 *
582 * @see #put(Object, Object)
583 */
584 public V get(Object key) {
585 Node<K,V> e;
586 return (e = getNode(hash(key), key)) == null ? null : e.value;
587 }
588
589 /**
590 * Implements Map.get and related methods
591 *
592 * @param hash hash for key
593 * @param key the key
594 * @return the node, or null if none
595 */
596 final Node<K,V> getNode(int hash, Object key) {
597 Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
598 if ((tab = table) != null && (n = tab.length) > 0 &&
599 (first = tab[(n - 1) & hash]) != null) {
600 if (first.hash == hash && // always check first node
601 ((k = first.key) == key || (key != null && key.equals(k))))
602 return first;
603 if ((e = first.next) != null) {
604 if (first instanceof TreeNode)
605 return ((TreeNode<K,V>)first).getTreeNode(this, hash, key);
606 do {
607 if (e.hash == hash &&
608 ((k = e.key) == key || (key != null && key.equals(k))))
609 return e;
610 } while ((e = e.next) != null);
611 }
612 }
613 return null;
614 }
615
616 /**
617 * Returns <tt>true</tt> if this map contains a mapping for the
618 * specified key.
619 *
620 * @param key The key whose presence in this map is to be tested
621 * @return <tt>true</tt> if this map contains a mapping for the specified
622 * key.
623 */
624 public boolean containsKey(Object key) {
625 return getNode(hash(key), key) != null;
626 }
627
628 /**
629 * Associates the specified value with the specified key in this map.
630 * If the map previously contained a mapping for the key, the old
631 * value is replaced.
632 *
633 * @param key key with which the specified value is to be associated
634 * @param value value to be associated with the specified key
635 * @return the previous value associated with <tt>key</tt>, or
636 * <tt>null</tt> if there was no mapping for <tt>key</tt>.
637 * (A <tt>null</tt> return can also indicate that the map
638 * previously associated <tt>null</tt> with <tt>key</tt>.)
639 */
640 public V put(K key, V value) {
641 return putVal(hash(key), key, value, false, true);
642 }
643
644 /**
645 * Implements Map.put and related methods
646 *
647 * @param hash hash for key
648 * @param key the key
649 * @param value the value to put
650 * @param onlyIfAbsent if true, don't change existing value
651 * @param evict if false, the table is in creation mode.
652 * @return previous value, or null if none
653 */
654 final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
655 boolean evict) {
656 Node<K,V>[] tab; Node<K,V> p; int n, i;
657 if ((tab = table) == null || (n = tab.length) == 0)
658 n = (tab = resize()).length;
659 if ((p = tab[i = (n - 1) & hash]) == null)
660 tab[i] = newNode(hash, key, value, null);
661 else {
662 Node<K,V> e; K k;
663 if (p.hash == hash &&
664 ((k = p.key) == key || (key != null && key.equals(k))))
665 e = p;
666 else if (p instanceof TreeNode)
667 e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
668 else {
669 for (int binCount = 0; ; ++binCount) {
670 if ((e = p.next) == null) {
671 p.next = newNode(hash, key, value, null);
672 if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
673 treeifyBin(tab, hash);
674 break;
675 }
676 if (e.hash == hash &&
677 ((k = e.key) == key || (key != null && key.equals(k))))
678 break;
679 p = e;
680 }
681 }
682 if (e != null) { // existing mapping for key
683 V oldValue = e.value;
684 if (!onlyIfAbsent || oldValue == null)
685 e.value = value;
686 afterNodeAccess(e);
687 return oldValue;
688 }
689 }
690 ++modCount;
691 if (++size > threshold)
692 resize();
693 afterNodeInsertion(evict);
694 return null;
695 }
696
697 /**
698 * Initializes or doubles table size. If null, allocates in
699 * accord with initial capacity target held in field threshold.
700 * Otherwise, because we are using power-of-two expansion, the
701 * elements from each bin must either stay at same index, or move
702 * with a power of two offset in the new table.
703 *
704 * @return the table
705 */
706 final Node<K,V>[] resize() {
707 Node<K,V>[] oldTab = table;
708 int oldCap = (oldTab == null) ? 0 : oldTab.length;
709 int oldThr = threshold;
710 int newCap, newThr = 0;
711 if (oldCap > 0) {
712 if (oldCap >= MAXIMUM_CAPACITY) {
713 threshold = Integer.MAX_VALUE;
714 return oldTab;
715 }
716 else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
717 oldCap >= DEFAULT_INITIAL_CAPACITY)
718 newThr = oldThr << 1; // double threshold
719 }
720 else if (oldThr > 0) // initial capacity was placed in threshold
721 newCap = oldThr;
722 else { // zero initial threshold signifies using defaults
723 newCap = DEFAULT_INITIAL_CAPACITY;
724 newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
725 }
726 if (newThr == 0) {
727 float ft = (float)newCap * loadFactor;
728 newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
729 (int)ft : Integer.MAX_VALUE);
730 }
731 threshold = newThr;
732 @SuppressWarnings({"rawtypes","unchecked"})
733 Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
734 table = newTab;
735 if (oldTab != null) {
736 for (int j = 0; j < oldCap; ++j) {
737 Node<K,V> e;
738 if ((e = oldTab[j]) != null) {
739 oldTab[j] = null;
740 if (e.next == null)
741 newTab[e.hash & (newCap - 1)] = e;
742 else if (e instanceof TreeNode)
743 ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
744 else { // preserve order
745 Node<K,V> loHead = null, loTail = null;
746 Node<K,V> hiHead = null, hiTail = null;
747 Node<K,V> next;
748 do {
749 next = e.next;
750 if ((e.hash & oldCap) == 0) {
751 if (loTail == null)
752 loHead = e;
753 else
754 loTail.next = e;
755 loTail = e;
756 }
757 else {
758 if (hiTail == null)
759 hiHead = e;
760 else
761 hiTail.next = e;
762 hiTail = e;
763 }
764 } while ((e = next) != null);
765 if (loTail != null) {
766 loTail.next = null;
767 newTab[j] = loHead;
768 }
769 if (hiTail != null) {
770 hiTail.next = null;
771 newTab[j + oldCap] = hiHead;
772 }
773 }
774 }
775 }
776 }
777 return newTab;
778 }
779
780 /**
781 * Replaces all linked nodes in bin at index for given hash unless
782 * table is too small, in which case resizes instead.
783 */
784 final void treeifyBin(Node<K,V>[] tab, int hash) {
785 int n, index; Node<K,V> e;
786 if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
787 resize();
788 else if ((e = tab[index = (n - 1) & hash]) != null) {
789 TreeNode<K,V> hd = null, tl = null;
790 do {
791 TreeNode<K,V> p = replacementTreeNode(e, null);
792 if (tl == null)
793 hd = p;
794 else {
795 p.prev = tl;
796 tl.next = p;
797 }
798 tl = p;
799 } while ((e = e.next) != null);
800 if ((tab[index] = hd) != null)
801 hd.treeify(this, tab);
802 }
803 }
804
805 /**
806 * Copies all of the mappings from the specified map to this map.
807 * These mappings will replace any mappings that this map had for
808 * any of the keys currently in the specified map.
809 *
810 * @param m mappings to be stored in this map
811 * @throws NullPointerException if the specified map is null
812 */
813 public void putAll(Map<? extends K, ? extends V> m) {
814 putMapEntries(m, true);
815 }
816
817 /**
818 * Removes the mapping for the specified key from this map if present.
819 *
820 * @param key key whose mapping is to be removed from the map
821 * @return the previous value associated with <tt>key</tt>, or
822 * <tt>null</tt> if there was no mapping for <tt>key</tt>.
823 * (A <tt>null</tt> return can also indicate that the map
824 * previously associated <tt>null</tt> with <tt>key</tt>.)
825 */
826 public V remove(Object key) {
827 Node<K,V> e;
828 return (e = removeNode(hash(key), key, null, false, true)) == null ?
829 null : e.value;
830 }
831
832 /**
833 * Implements Map.remove and related methods
834 *
835 * @param hash hash for key
836 * @param key the key
837 * @param value the value to match if matchValue, else ignored
838 * @param matchValue if true only remove if value is equal
839 * @param movable if false do not move other nodes while removing
840 * @return the node, or null if none
841 */
842 final Node<K,V> removeNode(int hash, Object key, Object value,
843 boolean matchValue, boolean movable) {
844 Node<K,V>[] tab; Node<K,V> p; int n, index;
845 if ((tab = table) != null && (n = tab.length) > 0 &&
846 (p = tab[index = (n - 1) & hash]) != null) {
847 Node<K,V> node = null, e; K k; V v;
848 if (p.hash == hash &&
849 ((k = p.key) == key || (key != null && key.equals(k))))
850 node = p;
851 else if ((e = p.next) != null) {
852 if (p instanceof TreeNode)
853 node = ((TreeNode<K,V>)p).getTreeNode(this, hash, key);
854 else {
855 do {
856 if (e.hash == hash &&
857 ((k = e.key) == key ||
858 (key != null && key.equals(k)))) {
859 node = e;
860 break;
861 }
862 p = e;
863 } while ((e = e.next) != null);
864 }
865 }
866 if (node != null && (!matchValue || (v = node.value) == value ||
867 (value != null && value.equals(v)))) {
868 if (node instanceof TreeNode)
869 ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
870 else if (node == p)
871 tab[index] = node.next;
872 else
873 p.next = node.next;
874 ++modCount;
875 --size;
876 afterNodeRemoval(node);
877 return node;
878 }
879 }
880 return null;
881 }
882
883 /**
884 * Removes all of the mappings from this map.
885 * The map will be empty after this call returns.
886 */
887 public void clear() {
888 Node<K,V>[] tab;
889 modCount++;
890 if ((tab = table) != null && size > 0) {
891 size = 0;
892 for (int i = 0; i < tab.length; ++i)
893 tab[i] = null;
894 }
895 }
896
897 /**
898 * Returns <tt>true</tt> if this map maps one or more keys to the
899 * specified value.
900 *
901 * @param value value whose presence in this map is to be tested
902 * @return <tt>true</tt> if this map maps one or more keys to the
903 * specified value
904 */
905 public boolean containsValue(Object value) {
906 Node<K,V>[] tab; V v;
907 if ((tab = table) != null && size > 0) {
908 for (Node<K, V> e : tab) {
909 for (; e != null; e = e.next) {
910 if ((v = e.value) == value ||
911 (value != null && value.equals(v)))
912 return true;
913 }
914 }
915 }
916 return false;
917 }
918
919 /**
920 * Returns a {@link Set} view of the keys contained in this map.
921 * The set is backed by the map, so changes to the map are
922 * reflected in the set, and vice-versa. If the map is modified
923 * while an iteration over the set is in progress (except through
924 * the iterator's own <tt>remove</tt> operation), the results of
925 * the iteration are undefined. The set supports element removal,
926 * which removes the corresponding mapping from the map, via the
927 * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
928 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
929 * operations. It does not support the <tt>add</tt> or <tt>addAll</tt>
930 * operations.
931 *
932 * @return a set view of the keys contained in this map
933 */
934 public Set<K> keySet() {
935 Set<K> ks;
936 return (ks = keySet) == null ? (keySet = new KeySet()) : ks;
937 }
938
939 final class KeySet extends AbstractSet<K> {
940 public final int size() { return size; }
941 public final void clear() { HashMap.this.clear(); }
942 public final Iterator<K> iterator() { return new KeyIterator(); }
943 public final boolean contains(Object o) { return containsKey(o); }
944 public final boolean remove(Object key) {
945 return removeNode(hash(key), key, null, false, true) != null;
946 }
947 public final Spliterator<K> spliterator() {
948 return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
949 }
950 public final void forEach(Consumer<? super K> action) {
951 Node<K,V>[] tab;
952 if (action == null)
953 throw new NullPointerException();
954 if (size > 0 && (tab = table) != null) {
955 int mc = modCount;
956 for (Node<K, V> e : tab) {
957 for (; e != null; e = e.next)
958 action.accept(e.key);
959 }
960 if (modCount != mc)
961 throw new ConcurrentModificationException();
962 }
963 }
964 }
965
966 /**
967 * Returns a {@link Collection} view of the values contained in this map.
968 * The collection is backed by the map, so changes to the map are
969 * reflected in the collection, and vice-versa. If the map is
970 * modified while an iteration over the collection is in progress
971 * (except through the iterator's own <tt>remove</tt> operation),
972 * the results of the iteration are undefined. The collection
973 * supports element removal, which removes the corresponding
974 * mapping from the map, via the <tt>Iterator.remove</tt>,
975 * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
976 * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not
977 * support the <tt>add</tt> or <tt>addAll</tt> operations.
978 *
979 * @return a view of the values contained in this map
980 */
981 public Collection<V> values() {
982 Collection<V> vs;
983 return (vs = values) == null ? (values = new Values()) : vs;
984 }
985
986 final class Values extends AbstractCollection<V> {
987 public final int size() { return size; }
988 public final void clear() { HashMap.this.clear(); }
989 public final Iterator<V> iterator() { return new ValueIterator(); }
990 public final boolean contains(Object o) { return containsValue(o); }
991 public final Spliterator<V> spliterator() {
992 return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
993 }
994 public final void forEach(Consumer<? super V> action) {
995 Node<K,V>[] tab;
996 if (action == null)
997 throw new NullPointerException();
998 if (size > 0 && (tab = table) != null) {
999 int mc = modCount;
1000 for (Node<K, V> e : tab) {
1001 for (; e != null; e = e.next)
1002 action.accept(e.value);
1003 }
1004 if (modCount != mc)
1005 throw new ConcurrentModificationException();
1006 }
1007 }
1008 }
1009
1010 /**
1011 * Returns a {@link Set} view of the mappings contained in this map.
1012 * The set is backed by the map, so changes to the map are
1013 * reflected in the set, and vice-versa. If the map is modified
1014 * while an iteration over the set is in progress (except through
1015 * the iterator's own <tt>remove</tt> operation, or through the
1016 * <tt>setValue</tt> operation on a map entry returned by the
1017 * iterator) the results of the iteration are undefined. The set
1018 * supports element removal, which removes the corresponding
1019 * mapping from the map, via the <tt>Iterator.remove</tt>,
1020 * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
1021 * <tt>clear</tt> operations. It does not support the
1022 * <tt>add</tt> or <tt>addAll</tt> operations.
1023 *
1024 * @return a set view of the mappings contained in this map
1025 */
1026 public Set<Map.Entry<K,V>> entrySet() {
1027 Set<Map.Entry<K,V>> es;
1028 return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
1029 }
1030
1031 final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
1032 public final int size() { return size; }
1033 public final void clear() { HashMap.this.clear(); }
1034 public final Iterator<Map.Entry<K,V>> iterator() {
1035 return new EntryIterator();
1036 }
1037 public final boolean contains(Object o) {
1038 if (!(o instanceof Map.Entry))
1039 return false;
1040 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
1041 Object key = e.getKey();
1042 Node<K,V> candidate = getNode(hash(key), key);
1043 return candidate != null && candidate.equals(e);
1044 }
1045 public final boolean remove(Object o) {
1046 if (o instanceof Map.Entry) {
1047 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
1048 Object key = e.getKey();
1049 Object value = e.getValue();
1050 return removeNode(hash(key), key, value, true, true) != null;
1051 }
1052 return false;
1053 }
1054 public final Spliterator<Map.Entry<K,V>> spliterator() {
1055 return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
1056 }
1057 public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
1058 Node<K,V>[] tab;
1059 if (action == null)
1060 throw new NullPointerException();
1061 if (size > 0 && (tab = table) != null) {
1062 int mc = modCount;
1063 for (Node<K, V> e : tab) {
1064 for (; e != null; e = e.next)
1065 action.accept(e);
1066 }
1067 if (modCount != mc)
1068 throw new ConcurrentModificationException();
1069 }
1070 }
1071 }
1072
1073 // Overrides of JDK8 Map extension methods
1074
1075 @Override
1076 public V getOrDefault(Object key, V defaultValue) {
1077 Node<K,V> e;
1078 return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
1079 }
1080
1081 @Override
1082 public V putIfAbsent(K key, V value) {
1083 return putVal(hash(key), key, value, true, true);
1084 }
1085
1086 @Override
1087 public boolean remove(Object key, Object value) {
1088 return removeNode(hash(key), key, value, true, true) != null;
1089 }
1090
1091 @Override
1092 public boolean replace(K key, V oldValue, V newValue) {
1093 Node<K,V> e; V v;
1094 if ((e = getNode(hash(key), key)) != null &&
1095 ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
1096 e.value = newValue;
1097 afterNodeAccess(e);
1098 return true;
1099 }
1100 return false;
1101 }
1102
1103 @Override
1104 public V replace(K key, V value) {
1105 Node<K,V> e;
1106 if ((e = getNode(hash(key), key)) != null) {
1107 V oldValue = e.value;
1108 e.value = value;
1109 afterNodeAccess(e);
1110 return oldValue;
1111 }
1112 return null;
1113 }
1114
1115 @Override
1116 public V computeIfAbsent(K key,
1117 Function<? super K, ? extends V> mappingFunction) {
1118 if (mappingFunction == null)
1119 throw new NullPointerException();
1120 int hash = hash(key);
1121 Node<K,V>[] tab; Node<K,V> first; int n, i;
1122 int binCount = 0;
1123 TreeNode<K,V> t = null;
1124 Node<K,V> old = null;
1125 if (size > threshold || (tab = table) == null ||
1126 (n = tab.length) == 0)
1127 n = (tab = resize()).length;
1128 if ((first = tab[i = (n - 1) & hash]) != null) {
1129 if (first instanceof TreeNode)
1130 old = (t = (TreeNode<K,V>)first).getTreeNode(this, hash, key);
1131 else {
1132 Node<K,V> e = first; K k;
1133 do {
1134 if (e.hash == hash &&
1135 ((k = e.key) == key || (key != null && key.equals(k)))) {
1136 old = e;
1137 break;
1138 }
1139 ++binCount;
1140 } while ((e = e.next) != null);
1141 }
1142 V oldValue;
1143 if (old != null && (oldValue = old.value) != null) {
1144 afterNodeAccess(old);
1145 return oldValue;
1146 }
1147 }
1148 V v = mappingFunction.apply(key);
1149 if (v == null) {
1150 return null;
1151 } else if (old != null) {
1152 old.value = v;
1153 afterNodeAccess(old);
1154 return v;
1155 }
1156 else if (t != null)
1157 t.putTreeVal(this, tab, hash, key, v);
1158 else {
1159 tab[i] = newNode(hash, key, v, first);
1160 if (binCount >= TREEIFY_THRESHOLD - 1)
1161 treeifyBin(tab, hash);
1162 }
1163 ++modCount;
1164 ++size;
1165 afterNodeInsertion(true);
1166 return v;
1167 }
1168
1169 public V computeIfPresent(K key,
1170 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1171 if (remappingFunction == null)
1172 throw new NullPointerException();
1173 Node<K,V> e; V oldValue;
1174 int hash = hash(key);
1175 if ((e = getNode(hash, key)) != null &&
1176 (oldValue = e.value) != null) {
1177 V v = remappingFunction.apply(key, oldValue);
1178 if (v != null) {
1179 e.value = v;
1180 afterNodeAccess(e);
1181 return v;
1182 }
1183 else
1184 removeNode(hash, key, null, false, true);
1185 }
1186 return null;
1187 }
1188
1189 @Override
1190 public V compute(K key,
1191 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1192 if (remappingFunction == null)
1193 throw new NullPointerException();
1194 int hash = hash(key);
1195 Node<K,V>[] tab; Node<K,V> first; int n, i;
1196 int binCount = 0;
1197 TreeNode<K,V> t = null;
1198 Node<K,V> old = null;
1199 if (size > threshold || (tab = table) == null ||
1200 (n = tab.length) == 0)
1201 n = (tab = resize()).length;
1202 if ((first = tab[i = (n - 1) & hash]) != null) {
1203 if (first instanceof TreeNode)
1204 old = (t = (TreeNode<K,V>)first).getTreeNode(this, hash, key);
1205 else {
1206 Node<K,V> e = first; K k;
1207 do {
1208 if (e.hash == hash &&
1209 ((k = e.key) == key || (key != null && key.equals(k)))) {
1210 old = e;
1211 break;
1212 }
1213 ++binCount;
1214 } while ((e = e.next) != null);
1215 }
1216 }
1217 V oldValue = (old == null) ? null : old.value;
1218 V v = remappingFunction.apply(key, oldValue);
1219 if (old != null) {
1220 if (v != null) {
1221 old.value = v;
1222 afterNodeAccess(old);
1223 }
1224 else
1225 removeNode(hash, key, null, false, true);
1226 }
1227 else if (v != null) {
1228 if (t != null)
1229 t.putTreeVal(this, tab, hash, key, v);
1230 else {
1231 tab[i] = newNode(hash, key, v, first);
1232 if (binCount >= TREEIFY_THRESHOLD - 1)
1233 treeifyBin(tab, hash);
1234 }
1235 ++modCount;
1236 ++size;
1237 afterNodeInsertion(true);
1238 }
1239 return v;
1240 }
1241
1242 @Override
1243 public V merge(K key, V value,
1244 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1245 if (value == null)
1246 throw new NullPointerException();
1247 if (remappingFunction == null)
1248 throw new NullPointerException();
1249 int hash = hash(key);
1250 Node<K,V>[] tab; Node<K,V> first; int n, i;
1251 int binCount = 0;
1252 TreeNode<K,V> t = null;
1253 Node<K,V> old = null;
1254 if (size > threshold || (tab = table) == null ||
1255 (n = tab.length) == 0)
1256 n = (tab = resize()).length;
1257 if ((first = tab[i = (n - 1) & hash]) != null) {
1258 if (first instanceof TreeNode)
1259 old = (t = (TreeNode<K,V>)first).getTreeNode(this, hash, key);
1260 else {
1261 Node<K,V> e = first; K k;
1262 do {
1263 if (e.hash == hash &&
1264 ((k = e.key) == key || (key != null && key.equals(k)))) {
1265 old = e;
1266 break;
1267 }
1268 ++binCount;
1269 } while ((e = e.next) != null);
1270 }
1271 }
1272 if (old != null) {
1273 V v;
1274 if (old.value != null)
1275 v = remappingFunction.apply(old.value, value);
1276 else
1277 v = value;
1278 if (v != null) {
1279 old.value = v;
1280 afterNodeAccess(old);
1281 }
1282 else
1283 removeNode(hash, key, null, false, true);
1284 return v;
1285 }
1286 if (value != null) {
1287 if (t != null)
1288 t.putTreeVal(this, tab, hash, key, value);
1289 else {
1290 tab[i] = newNode(hash, key, value, first);
1291 if (binCount >= TREEIFY_THRESHOLD - 1)
1292 treeifyBin(tab, hash);
1293 }
1294 ++modCount;
1295 ++size;
1296 afterNodeInsertion(true);
1297 }
1298 return value;
1299 }
1300
1301 @Override
1302 public void forEach(BiConsumer<? super K, ? super V> action) {
1303 Node<K,V>[] tab;
1304 if (action == null)
1305 throw new NullPointerException();
1306 if (size > 0 && (tab = table) != null) {
1307 int mc = modCount;
1308 for (Node<K, V> e : tab) {
1309 for (; e != null; e = e.next)
1310 action.accept(e.key, e.value);
1311 }
1312 if (modCount != mc)
1313 throw new ConcurrentModificationException();
1314 }
1315 }
1316
1317 @Override
1318 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1319 Node<K,V>[] tab;
1320 if (function == null)
1321 throw new NullPointerException();
1322 if (size > 0 && (tab = table) != null) {
1323 int mc = modCount;
1324 for (Node<K, V> e : tab) {
1325 for (; e != null; e = e.next) {
1326 e.value = function.apply(e.key, e.value);
1327 }
1328 }
1329 if (modCount != mc)
1330 throw new ConcurrentModificationException();
1331 }
1332 }
1333
1334 /* ------------------------------------------------------------ */
1335 // Cloning and serialization
1336
1337 /**
1338 * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
1339 * values themselves are not cloned.
1340 *
1341 * @return a shallow copy of this map
1342 */
1343 @SuppressWarnings("unchecked")
1344 @Override
1345 public Object clone() {
1346 HashMap<K,V> result;
1347 try {
1348 result = (HashMap<K,V>)super.clone();
1349 } catch (CloneNotSupportedException e) {
1350 // this shouldn't happen, since we are Cloneable
1351 throw new InternalError(e);
1352 }
1353 result.reinitialize();
1354 result.putMapEntries(this, false);
1355 return result;
1356 }
1357
1358 // These methods are also used when serializing HashSets
1359 final float loadFactor() { return loadFactor; }
1360 final int capacity() {
1361 return (table != null) ? table.length :
1362 (threshold > 0) ? threshold :
1363 DEFAULT_INITIAL_CAPACITY;
1364 }
1365
1366 /**
1367 * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
1368 * serialize it).
1369 *
1370 * @serialData The <i>capacity</i> of the HashMap (the length of the
1371 * bucket array) is emitted (int), followed by the
1372 * <i>size</i> (an int, the number of key-value
1373 * mappings), followed by the key (Object) and value (Object)
1374 * for each key-value mapping. The key-value mappings are
1375 * emitted in no particular order.
1376 */
1377 private void writeObject(java.io.ObjectOutputStream s)
1378 throws IOException {
1379 int buckets = capacity();
1380 // Write out the threshold, loadfactor, and any hidden stuff
1381 s.defaultWriteObject();
1382 s.writeInt(buckets);
1383 s.writeInt(size);
1384 internalWriteEntries(s);
1385 }
1386
1387 /**
1388 * Reconstitute the {@code HashMap} instance from a stream (i.e.,
1389 * deserialize it).
1390 */
1391 private void readObject(java.io.ObjectInputStream s)
1392 throws IOException, ClassNotFoundException {
1393 // Read in the threshold (ignored), loadfactor, and any hidden stuff
1394 s.defaultReadObject();
1395 reinitialize();
1396 if (loadFactor <= 0 || Float.isNaN(loadFactor))
1397 throw new InvalidObjectException("Illegal load factor: " +
1398 loadFactor);
1399 s.readInt(); // Read and ignore number of buckets
1400 int mappings = s.readInt(); // Read number of mappings (size)
1401 if (mappings < 0)
1402 throw new InvalidObjectException("Illegal mappings count: " +
1403 mappings);
1404 else if (mappings > 0) { // (if zero, use defaults)
1405 // Size the table using given load factor only if within
1406 // range of 0.25...4.0
1407 float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
1408 float fc = (float)mappings / lf + 1.0f;
1409 int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
1410 DEFAULT_INITIAL_CAPACITY :
1411 (fc >= MAXIMUM_CAPACITY) ?
1412 MAXIMUM_CAPACITY :
1413 tableSizeFor((int)fc));
1414 float ft = (float)cap * lf;
1415 threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
1416 (int)ft : Integer.MAX_VALUE);
1417 @SuppressWarnings({"rawtypes","unchecked"})
1418 Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
1419 table = tab;
1420
1421 // Read the keys and values, and put the mappings in the HashMap
1422 for (int i = 0; i < mappings; i++) {
1423 @SuppressWarnings("unchecked")
1424 K key = (K) s.readObject();
1425 @SuppressWarnings("unchecked")
1426 V value = (V) s.readObject();
1427 putVal(hash(key), key, value, false, false);
1428 }
1429 }
1430 }
1431
1432 /* ------------------------------------------------------------ */
1433 // iterators
1434
1435 abstract class HashIterator {
1436 Node<K,V> next; // next entry to return
1437 Node<K,V> current; // current entry
1438 int expectedModCount; // for fast-fail
1439 int index; // current slot
1440
1441 HashIterator() {
1442 expectedModCount = modCount;
1443 Node<K,V>[] t = table;
1444 current = next = null;
1445 index = 0;
1446 if (t != null && size > 0) { // advance to first entry
1447 do {} while (index < t.length && (next = t[index++]) == null);
1448 }
1449 }
1450
1451 public final boolean hasNext() {
1452 return next != null;
1453 }
1454
1455 final Node<K,V> nextNode() {
1456 Node<K,V>[] t;
1457 Node<K,V> e = next;
1458 if (modCount != expectedModCount)
1459 throw new ConcurrentModificationException();
1460 if (e == null)
1461 throw new NoSuchElementException();
1462 if ((next = (current = e).next) == null && (t = table) != null) {
1463 do {} while (index < t.length && (next = t[index++]) == null);
1464 }
1465 return e;
1466 }
1467
1468 public final void remove() {
1469 Node<K,V> p = current;
1470 if (p == null)
1471 throw new IllegalStateException();
1472 if (modCount != expectedModCount)
1473 throw new ConcurrentModificationException();
1474 current = null;
1475 K key = p.key;
1476 removeNode(hash(key), key, null, false, false);
1477 expectedModCount = modCount;
1478 }
1479 }
1480
1481 final class KeyIterator extends HashIterator
1482 implements Iterator<K> {
1483 public final K next() { return nextNode().key; }
1484 }
1485
1486 final class ValueIterator extends HashIterator
1487 implements Iterator<V> {
1488 public final V next() { return nextNode().value; }
1489 }
1490
1491 final class EntryIterator extends HashIterator
1492 implements Iterator<Map.Entry<K,V>> {
1493 public final Map.Entry<K,V> next() { return nextNode(); }
1494 }
1495
1496 /* ------------------------------------------------------------ */
1497 // spliterators
1498
1499 static class HashMapSpliterator<K,V> {
1500 final HashMap<K,V> map;
1501 Node<K,V> current; // current node
1502 int index; // current index, modified on advance/split
1503 int fence; // one past last index
1504 int est; // size estimate
1505 int expectedModCount; // for comodification checks
1506
1507 HashMapSpliterator(HashMap<K,V> m, int origin,
1508 int fence, int est,
1509 int expectedModCount) {
1510 this.map = m;
1511 this.index = origin;
1512 this.fence = fence;
1513 this.est = est;
1514 this.expectedModCount = expectedModCount;
1515 }
1516
1517 final int getFence() { // initialize fence and size on first use
1518 int hi;
1519 if ((hi = fence) < 0) {
1520 HashMap<K,V> m = map;
1521 est = m.size;
1522 expectedModCount = m.modCount;
1523 Node<K,V>[] tab = m.table;
1524 hi = fence = (tab == null) ? 0 : tab.length;
1525 }
1526 return hi;
1527 }
1528
1529 public final long estimateSize() {
1530 getFence(); // force init
1531 return (long) est;
1532 }
1533 }
1534
1535 static final class KeySpliterator<K,V>
1536 extends HashMapSpliterator<K,V>
1537 implements Spliterator<K> {
1538 KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
1539 int expectedModCount) {
1540 super(m, origin, fence, est, expectedModCount);
1541 }
1542
1543 public KeySpliterator<K,V> trySplit() {
1544 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1545 return (lo >= mid || current != null) ? null :
1546 new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
1547 expectedModCount);
1548 }
1549
1550 public void forEachRemaining(Consumer<? super K> action) {
1551 int i, hi, mc;
1552 if (action == null)
1553 throw new NullPointerException();
1554 HashMap<K,V> m = map;
1555 Node<K,V>[] tab = m.table;
1556 if ((hi = fence) < 0) {
1557 mc = expectedModCount = m.modCount;
1558 hi = fence = (tab == null) ? 0 : tab.length;
1559 }
1560 else
1561 mc = expectedModCount;
1562 if (tab != null && tab.length >= hi &&
1563 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1564 Node<K,V> p = current;
1565 current = null;
1566 do {
1567 if (p == null)
1568 p = tab[i++];
1569 else {
1570 action.accept(p.key);
1571 p = p.next;
1572 }
1573 } while (p != null || i < hi);
1574 if (m.modCount != mc)
1575 throw new ConcurrentModificationException();
1576 }
1577 }
1578
1579 public boolean tryAdvance(Consumer<? super K> action) {
1580 int hi;
1581 if (action == null)
1582 throw new NullPointerException();
1583 Node<K,V>[] tab = map.table;
1584 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1585 while (current != null || index < hi) {
1586 if (current == null)
1587 current = tab[index++];
1588 else {
1589 K k = current.key;
1590 current = current.next;
1591 action.accept(k);
1592 if (map.modCount != expectedModCount)
1593 throw new ConcurrentModificationException();
1594 return true;
1595 }
1596 }
1597 }
1598 return false;
1599 }
1600
1601 public int characteristics() {
1602 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
1603 Spliterator.DISTINCT;
1604 }
1605 }
1606
1607 static final class ValueSpliterator<K,V>
1608 extends HashMapSpliterator<K,V>
1609 implements Spliterator<V> {
1610 ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
1611 int expectedModCount) {
1612 super(m, origin, fence, est, expectedModCount);
1613 }
1614
1615 public ValueSpliterator<K,V> trySplit() {
1616 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1617 return (lo >= mid || current != null) ? null :
1618 new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
1619 expectedModCount);
1620 }
1621
1622 public void forEachRemaining(Consumer<? super V> action) {
1623 int i, hi, mc;
1624 if (action == null)
1625 throw new NullPointerException();
1626 HashMap<K,V> m = map;
1627 Node<K,V>[] tab = m.table;
1628 if ((hi = fence) < 0) {
1629 mc = expectedModCount = m.modCount;
1630 hi = fence = (tab == null) ? 0 : tab.length;
1631 }
1632 else
1633 mc = expectedModCount;
1634 if (tab != null && tab.length >= hi &&
1635 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1636 Node<K,V> p = current;
1637 current = null;
1638 do {
1639 if (p == null)
1640 p = tab[i++];
1641 else {
1642 action.accept(p.value);
1643 p = p.next;
1644 }
1645 } while (p != null || i < hi);
1646 if (m.modCount != mc)
1647 throw new ConcurrentModificationException();
1648 }
1649 }
1650
1651 public boolean tryAdvance(Consumer<? super V> action) {
1652 int hi;
1653 if (action == null)
1654 throw new NullPointerException();
1655 Node<K,V>[] tab = map.table;
1656 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1657 while (current != null || index < hi) {
1658 if (current == null)
1659 current = tab[index++];
1660 else {
1661 V v = current.value;
1662 current = current.next;
1663 action.accept(v);
1664 if (map.modCount != expectedModCount)
1665 throw new ConcurrentModificationException();
1666 return true;
1667 }
1668 }
1669 }
1670 return false;
1671 }
1672
1673 public int characteristics() {
1674 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
1675 }
1676 }
1677
1678 static final class EntrySpliterator<K,V>
1679 extends HashMapSpliterator<K,V>
1680 implements Spliterator<Map.Entry<K,V>> {
1681 EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
1682 int expectedModCount) {
1683 super(m, origin, fence, est, expectedModCount);
1684 }
1685
1686 public EntrySpliterator<K,V> trySplit() {
1687 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1688 return (lo >= mid || current != null) ? null :
1689 new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
1690 expectedModCount);
1691 }
1692
1693 public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
1694 int i, hi, mc;
1695 if (action == null)
1696 throw new NullPointerException();
1697 HashMap<K,V> m = map;
1698 Node<K,V>[] tab = m.table;
1699 if ((hi = fence) < 0) {
1700 mc = expectedModCount = m.modCount;
1701 hi = fence = (tab == null) ? 0 : tab.length;
1702 }
1703 else
1704 mc = expectedModCount;
1705 if (tab != null && tab.length >= hi &&
1706 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1707 Node<K,V> p = current;
1708 current = null;
1709 do {
1710 if (p == null)
1711 p = tab[i++];
1712 else {
1713 action.accept(p);
1714 p = p.next;
1715 }
1716 } while (p != null || i < hi);
1717 if (m.modCount != mc)
1718 throw new ConcurrentModificationException();
1719 }
1720 }
1721
1722 public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
1723 int hi;
1724 if (action == null)
1725 throw new NullPointerException();
1726 Node<K,V>[] tab = map.table;
1727 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1728 while (current != null || index < hi) {
1729 if (current == null)
1730 current = tab[index++];
1731 else {
1732 Node<K,V> e = current;
1733 current = current.next;
1734 action.accept(e);
1735 if (map.modCount != expectedModCount)
1736 throw new ConcurrentModificationException();
1737 return true;
1738 }
1739 }
1740 }
1741 return false;
1742 }
1743
1744 public int characteristics() {
1745 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
1746 Spliterator.DISTINCT;
1747 }
1748 }
1749
1750 /* ------------------------------------------------------------ */
1751 // LinkedHashMap support
1752
1753
1754 /*
1755 * The following package-protected methods are designed to be
1756 * overridden by LinkedHashMap, but not by any other subclass.
1757 * Nearly all other internal methods are also package-protected
1758 * but are declared final, so can be used by LinkedHashMap, view
1759 * classes, and HashSet.
1760 */
1761
1762 // Create a regular (non-tree) node
1763 Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
1764 return new Node<>(hash, key, value, next);
1765 }
1766
1767 // For conversion from TreeNodes to plain nodes
1768 Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
1769 return new Node<>(p.hash, p.key, p.value, next);
1770 }
1771
1772 // Create a tree bin node
1773 TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
1774 return new TreeNode<>(hash, key, value, next);
1775 }
1776
1777 // For treeifyBin
1778 TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
1779 return new TreeNode<>(p.hash, p.key, p.value, next);
1780 }
1781
1782 /**
1783 * Reset to initial default state. Called by clone and readObject.
1784 */
1785 void reinitialize() {
1786 table = null;
1787 entrySet = null;
1788 keySet = null;
1789 values = null;
1790 modCount = 0;
1791 threshold = 0;
1792 size = 0;
1793 }
1794
1795 // Callbacks to allow LinkedHashMap post-actions
1796 void afterNodeAccess(Node<K,V> p) { }
1797 void afterNodeInsertion(boolean evict) { }
1798 void afterNodeRemoval(Node<K,V> p) { }
1799
1800 // Called only from writeObject, to ensure compatible ordering.
1801 void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
1802 Node<K,V>[] tab;
1803 if (size > 0 && (tab = table) != null) {
1804 for (Node<K, V> e : tab) {
1805 for (; e != null; e = e.next) {
1806 s.writeObject(e.key);
1807 s.writeObject(e.value);
1808 }
1809 }
1810 }
1811 }
1812
1813 /* ------------------------------------------------------------ */
1814 // Tree bins
1815
1816 /**
1817 * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
1818 * extends Node) so can be used as extension of either regular or
1819 * linked node.
1820 */
1821 static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
1822 TreeNode<K,V> parent; // red-black tree links
1823 TreeNode<K,V> left;
1824 TreeNode<K,V> right;
1825 TreeNode<K,V> prev; // needed to unlink next upon deletion
1826 boolean red;
1827 TreeNode(int hash, K key, V val, Node<K,V> next) {
1828 super(hash, key, val, next);
1829 }
1830
1831 /**
1832 * Returns root of tree containing this node.
1833 */
1834 final TreeNode<K,V> root() {
1835 for (TreeNode<K,V> r = this, p;;) {
1836 if ((p = r.parent) == null)
1837 return r;
1838 r = p;
1839 }
1840 }
1841
1842 /**
1843 * Ensures that the given root is the first node of its bin.
1844 */
1845 static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
1846 int n;
1847 if (root != null && tab != null && (n = tab.length) > 0) {
1848 int index = (n - 1) & root.hash;
1849 TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
1850 if (root != first) {
1851 Node<K,V> rn;
1852 tab[index] = root;
1853 TreeNode<K,V> rp = root.prev;
1854 if ((rn = root.next) != null)
1855 ((TreeNode<K,V>)rn).prev = rp;
1856 if (rp != null)
1857 rp.next = rn;
1858 if (first != null)
1859 first.prev = root;
1860 root.next = first;
1861 root.prev = null;
1862 }
1863 assert checkInvariants(root);
1864 }
1865 }
1866
1867 /**
1868 * Finds the node starting at root p with the given hash and key.
1869 * The kc argument caches comparableClassFor(key) upon first use
1870 * comparing keys.
1871 */
1872 final TreeNode<K,V> find(HashMap<K,V> map, int h, Object k, Class<?> kc) {
1873 TreeNode<K,V> p = this;
1874 do {
1875 int ph, dir; K pk;
1876 TreeNode<K,V> pl = p.left, pr = p.right, q;
1877 if ((ph = p.hash) > h)
1878 p = pl;
1879 else if (ph < h)
1880 p = pr;
1881 else if ((pk = p.key) == k || (k != null && k.equals(pk)))
1882 return p;
1883 else if (pl == null)
1884 p = pr;
1885 else if (pr == null)
1886 p = pl;
1887 else if ((kc != null ||
1888 (kc = map.comparableClassFor(k)) != null) &&
1889 (dir = compareComparables(kc, k, pk)) != 0)
1890 p = (dir < 0) ? pl : pr;
1891 else if ((q = pr.find(map, h, k, kc)) != null)
1892 return q;
1893 else
1894 p = pl;
1895 } while (p != null);
1896 return null;
1897 }
1898
1899 /**
1900 * Calls find for root node.
1901 */
1902 final TreeNode<K,V> getTreeNode(HashMap<K,V> map, int h, Object k) {
1903 return ((parent != null) ? root() : this).find(map, h, k, null);
1904 }
1905
1906 /**
1907 * Tie-breaking utility for ordering insertions when equal
1908 * hashCodes and non-comparable. We don't require a total
1909 * order, just a consistent insertion rule to maintain
1910 * equivalence across rebalancings. Tie-breaking further than
1911 * necessary simplifies testing a bit.
1912 */
1913 static int tieBreakOrder(Object a, Object b) {
1914 int d;
1915 if (a == null || b == null ||
1916 (d = a.getClass().getName().
1917 compareTo(b.getClass().getName())) == 0)
1918 d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
1919 -1 : 1);
1920 return d;
1921 }
1922
1923 /**
1924 * Forms tree of the nodes linked from this node.
1925 * @return root of tree
1926 */
1927 final void treeify(HashMap<K,V> map, Node<K,V>[] tab) {
1928 TreeNode<K,V> root = null;
1929 for (TreeNode<K,V> x = this, next; x != null; x = next) {
1930 next = (TreeNode<K,V>)x.next;
1931 x.left = x.right = null;
1932 if (root == null) {
1933 x.parent = null;
1934 x.red = false;
1935 root = x;
1936 }
1937 else {
1938 K k = x.key;
1939 int h = x.hash;
1940 Class<?> kc = null;
1941 for (TreeNode<K,V> p = root;;) {
1942 int dir, ph;
1943 K pk = p.key;
1944 if ((ph = p.hash) > h)
1945 dir = -1;
1946 else if (ph < h)
1947 dir = 1;
1948 else if ((kc == null &&
1949 (kc = map.comparableClassFor(k)) == null) ||
1950 (dir = compareComparables(kc, k, pk)) == 0)
1951 dir = tieBreakOrder(k, pk);
1952
1953 TreeNode<K,V> xp = p;
1954 if ((p = (dir <= 0) ? p.left : p.right) == null) {
1955 x.parent = xp;
1956 if (dir <= 0)
1957 xp.left = x;
1958 else
1959 xp.right = x;
1960 root = balanceInsertion(root, x);
1961 break;
1962 }
1963 }
1964 }
1965 }
1966 moveRootToFront(tab, root);
1967 }
1968
1969 /**
1970 * Returns a list of non-TreeNodes replacing those linked from
1971 * this node.
1972 */
1973 final Node<K,V> untreeify(HashMap<K,V> map) {
1974 Node<K,V> hd = null, tl = null;
1975 for (Node<K,V> q = this; q != null; q = q.next) {
1976 Node<K,V> p = map.replacementNode(q, null);
1977 if (tl == null)
1978 hd = p;
1979 else
1980 tl.next = p;
1981 tl = p;
1982 }
1983 return hd;
1984 }
1985
1986 /**
1987 * Tree version of putVal.
1988 */
1989 final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
1990 int h, K k, V v) {
1991 Class<?> kc = null;
1992 boolean searched = false;
1993 TreeNode<K,V> root = (parent != null) ? root() : this;
1994 for (TreeNode<K,V> p = root;;) {
1995 int dir, ph; K pk;
1996 if ((ph = p.hash) > h)
1997 dir = -1;
1998 else if (ph < h)
1999 dir = 1;
2000 else if ((pk = p.key) == k || (k != null && k.equals(pk)))
2001 return p;
2002 else if ((kc == null &&
2003 (kc = map.comparableClassFor(k)) == null) ||
2004 (dir = compareComparables(kc, k, pk)) == 0) {
2005 if (!searched) {
2006 TreeNode<K,V> q, ch;
2007 searched = true;
2008 if (((ch = p.left) != null &&
2009 (q = ch.find(map, h, k, kc)) != null) ||
2010 ((ch = p.right) != null &&
2011 (q = ch.find(map, h, k, kc)) != null))
2012 return q;
2013 }
2014 dir = tieBreakOrder(k, pk);
2015 }
2016
2017 TreeNode<K,V> xp = p;
2018 if ((p = (dir <= 0) ? p.left : p.right) == null) {
2019 Node<K,V> xpn = xp.next;
2020 TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
2021 if (dir <= 0)
2022 xp.left = x;
2023 else
2024 xp.right = x;
2025 xp.next = x;
2026 x.parent = x.prev = xp;
2027 if (xpn != null)
2028 ((TreeNode<K,V>)xpn).prev = x;
2029 moveRootToFront(tab, balanceInsertion(root, x));
2030 return null;
2031 }
2032 }
2033 }
2034
2035 /**
2036 * Removes the given node, that must be present before this call.
2037 * This is messier than typical red-black deletion code because we
2038 * cannot swap the contents of an interior node with a leaf
2039 * successor that is pinned by "next" pointers that are accessible
2040 * independently during traversal. So instead we swap the tree
2041 * linkages. If the current tree appears to have too few nodes,
2042 * the bin is converted back to a plain bin. (The test triggers
2043 * somewhere between 2 and 6 nodes, depending on tree structure).
2044 */
2045 final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
2046 boolean movable) {
2047 int n;
2048 if (tab == null || (n = tab.length) == 0)
2049 return;
2050 int index = (n - 1) & hash;
2051 TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
2052 TreeNode<K,V> succ = (TreeNode<K,V>)next, pred = prev;
2053 if (pred == null)
2054 tab[index] = first = succ;
2055 else
2056 pred.next = succ;
2057 if (succ != null)
2058 succ.prev = pred;
2059 if (first == null)
2060 return;
2061 if (root.parent != null)
2062 root = root.root();
2063 if (root == null || root.right == null ||
2064 (rl = root.left) == null || rl.left == null) {
2065 tab[index] = first.untreeify(map); // too small
2066 return;
2067 }
2068 TreeNode<K,V> p = this, pl = left, pr = right, replacement;
2069 if (pl != null && pr != null) {
2070 TreeNode<K,V> s = pr, sl;
2071 while ((sl = s.left) != null) // find successor
2072 s = sl;
2073 boolean c = s.red; s.red = p.red; p.red = c; // swap colors
2074 TreeNode<K,V> sr = s.right;
2075 TreeNode<K,V> pp = p.parent;
2076 if (s == pr) { // p was s's direct parent
2077 p.parent = s;
2078 s.right = p;
2079 }
2080 else {
2081 TreeNode<K,V> sp = s.parent;
2082 if ((p.parent = sp) != null) {
2083 if (s == sp.left)
2084 sp.left = p;
2085 else
2086 sp.right = p;
2087 }
2088 if ((s.right = pr) != null)
2089 pr.parent = s;
2090 }
2091 p.left = null;
2092 if ((p.right = sr) != null)
2093 sr.parent = p;
2094 if ((s.left = pl) != null)
2095 pl.parent = s;
2096 if ((s.parent = pp) == null)
2097 root = s;
2098 else if (p == pp.left)
2099 pp.left = s;
2100 else
2101 pp.right = s;
2102 if (sr != null)
2103 replacement = sr;
2104 else
2105 replacement = p;
2106 }
2107 else if (pl != null)
2108 replacement = pl;
2109 else if (pr != null)
2110 replacement = pr;
2111 else
2112 replacement = p;
2113 if (replacement != p) {
2114 TreeNode<K,V> pp = replacement.parent = p.parent;
2115 if (pp == null)
2116 root = replacement;
2117 else if (p == pp.left)
2118 pp.left = replacement;
2119 else
2120 pp.right = replacement;
2121 p.left = p.right = p.parent = null;
2122 }
2123
2124 TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);
2125
2126 if (replacement == p) { // detach
2127 TreeNode<K,V> pp = p.parent;
2128 p.parent = null;
2129 if (pp != null) {
2130 if (p == pp.left)
2131 pp.left = null;
2132 else if (p == pp.right)
2133 pp.right = null;
2134 }
2135 }
2136 if (movable)
2137 moveRootToFront(tab, r);
2138 }
2139
2140 /**
2141 * Splits nodes in a tree bin into lower and upper tree bins,
2142 * or untreeifies if now too small. Called only from resize;
2143 * see above discussion about split bits and indices.
2144 *
2145 * @param map the map
2146 * @param tab the table for recording bin heads
2147 * @param index the index of the table being split
2148 * @param bit the bit of hash to split on
2149 */
2150 final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
2151 TreeNode<K,V> b = this;
2152 // Relink into lo and hi lists, preserving order
2153 TreeNode<K,V> loHead = null, loTail = null;
2154 TreeNode<K,V> hiHead = null, hiTail = null;
2155 int lc = 0, hc = 0;
2156 for (TreeNode<K,V> e = b, next; e != null; e = next) {
2157 next = (TreeNode<K,V>)e.next;
2158 e.next = null;
2159 if ((e.hash & bit) == 0) {
2160 if ((e.prev = loTail) == null)
2161 loHead = e;
2162 else
2163 loTail.next = e;
2164 loTail = e;
2165 ++lc;
2166 }
2167 else {
2168 if ((e.prev = hiTail) == null)
2169 hiHead = e;
2170 else
2171 hiTail.next = e;
2172 hiTail = e;
2173 ++hc;
2174 }
2175 }
2176
2177 if (loHead != null) {
2178 if (lc <= UNTREEIFY_THRESHOLD)
2179 tab[index] = loHead.untreeify(map);
2180 else {
2181 tab[index] = loHead;
2182 if (hiHead != null) // (else is already treeified)
2183 loHead.treeify(map, tab);
2184 }
2185 }
2186 if (hiHead != null) {
2187 if (hc <= UNTREEIFY_THRESHOLD)
2188 tab[index + bit] = hiHead.untreeify(map);
2189 else {
2190 tab[index + bit] = hiHead;
2191 if (loHead != null)
2192 hiHead.treeify(map, tab);
2193 }
2194 }
2195 }
2196
2197 /* ------------------------------------------------------------ */
2198 // Red-black tree methods, all adapted from CLR
2199
2200 static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
2201 TreeNode<K,V> p) {
2202 TreeNode<K,V> r, pp, rl;
2203 if (p != null && (r = p.right) != null) {
2204 if ((rl = p.right = r.left) != null)
2205 rl.parent = p;
2206 if ((pp = r.parent = p.parent) == null)
2207 (root = r).red = false;
2208 else if (pp.left == p)
2209 pp.left = r;
2210 else
2211 pp.right = r;
2212 r.left = p;
2213 p.parent = r;
2214 }
2215 return root;
2216 }
2217
2218 static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
2219 TreeNode<K,V> p) {
2220 TreeNode<K,V> l, pp, lr;
2221 if (p != null && (l = p.left) != null) {
2222 if ((lr = p.left = l.right) != null)
2223 lr.parent = p;
2224 if ((pp = l.parent = p.parent) == null)
2225 (root = l).red = false;
2226 else if (pp.right == p)
2227 pp.right = l;
2228 else
2229 pp.left = l;
2230 l.right = p;
2231 p.parent = l;
2232 }
2233 return root;
2234 }
2235
2236 static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
2237 TreeNode<K,V> x) {
2238 x.red = true;
2239 for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {
2240 if ((xp = x.parent) == null) {
2241 x.red = false;
2242 return x;
2243 }
2244 else if (!xp.red || (xpp = xp.parent) == null)
2245 return root;
2246 if (xp == (xppl = xpp.left)) {
2247 if ((xppr = xpp.right) != null && xppr.red) {
2248 xppr.red = false;
2249 xp.red = false;
2250 xpp.red = true;
2251 x = xpp;
2252 }
2253 else {
2254 if (x == xp.right) {
2255 root = rotateLeft(root, x = xp);
2256 xpp = (xp = x.parent) == null ? null : xp.parent;
2257 }
2258 if (xp != null) {
2259 xp.red = false;
2260 if (xpp != null) {
2261 xpp.red = true;
2262 root = rotateRight(root, xpp);
2263 }
2264 }
2265 }
2266 }
2267 else {
2268 if (xppl != null && xppl.red) {
2269 xppl.red = false;
2270 xp.red = false;
2271 xpp.red = true;
2272 x = xpp;
2273 }
2274 else {
2275 if (x == xp.left) {
2276 root = rotateRight(root, x = xp);
2277 xpp = (xp = x.parent) == null ? null : xp.parent;
2278 }
2279 if (xp != null) {
2280 xp.red = false;
2281 if (xpp != null) {
2282 xpp.red = true;
2283 root = rotateLeft(root, xpp);
2284 }
2285 }
2286 }
2287 }
2288 }
2289 }
2290
2291 static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
2292 TreeNode<K,V> x) {
2293 for (TreeNode<K,V> xp, xpl, xpr;;) {
2294 if (x == null || x == root)
2295 return root;
2296 else if ((xp = x.parent) == null) {
2297 x.red = false;
2298 return x;
2299 }
2300 else if (x.red) {
2301 x.red = false;
2302 return root;
2303 }
2304 else if ((xpl = xp.left) == x) {
2305 if ((xpr = xp.right) != null && xpr.red) {
2306 xpr.red = false;
2307 xp.red = true;
2308 root = rotateLeft(root, xp);
2309 xpr = (xp = x.parent) == null ? null : xp.right;
2310 }
2311 if (xpr == null)
2312 x = xp;
2313 else {
2314 TreeNode<K,V> sl = xpr.left, sr = xpr.right;
2315 if ((sr == null || !sr.red) &&
2316 (sl == null || !sl.red)) {
2317 xpr.red = true;
2318 x = xp;
2319 }
2320 else {
2321 if (sr == null || !sr.red) {
2322 if (sl != null)
2323 sl.red = false;
2324 xpr.red = true;
2325 root = rotateRight(root, xpr);
2326 xpr = (xp = x.parent) == null ?
2327 null : xp.right;
2328 }
2329 if (xpr != null) {
2330 xpr.red = (xp == null) ? false : xp.red;
2331 if ((sr = xpr.right) != null)
2332 sr.red = false;
2333 }
2334 if (xp != null) {
2335 xp.red = false;
2336 root = rotateLeft(root, xp);
2337 }
2338 x = root;
2339 }
2340 }
2341 }
2342 else { // symmetric
2343 if (xpl != null && xpl.red) {
2344 xpl.red = false;
2345 xp.red = true;
2346 root = rotateRight(root, xp);
2347 xpl = (xp = x.parent) == null ? null : xp.left;
2348 }
2349 if (xpl == null)
2350 x = xp;
2351 else {
2352 TreeNode<K,V> sl = xpl.left, sr = xpl.right;
2353 if ((sl == null || !sl.red) &&
2354 (sr == null || !sr.red)) {
2355 xpl.red = true;
2356 x = xp;
2357 }
2358 else {
2359 if (sl == null || !sl.red) {
2360 if (sr != null)
2361 sr.red = false;
2362 xpl.red = true;
2363 root = rotateLeft(root, xpl);
2364 xpl = (xp = x.parent) == null ?
2365 null : xp.left;
2366 }
2367 if (xpl != null) {
2368 xpl.red = (xp == null) ? false : xp.red;
2369 if ((sl = xpl.left) != null)
2370 sl.red = false;
2371 }
2372 if (xp != null) {
2373 xp.red = false;
2374 root = rotateRight(root, xp);
2375 }
2376 x = root;
2377 }
2378 }
2379 }
2380 }
2381 }
2382
2383 /**
2384 * Recursive invariant check
2385 */
2386 static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
2387 TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
2388 tb = t.prev, tn = (TreeNode<K,V>)t.next;
2389 if (tb != null && tb.next != t)
2390 return false;
2391 if (tn != null && tn.prev != t)
2392 return false;
2393 if (tp != null && t != tp.left && t != tp.right)
2394 return false;
2395 if (tl != null && (tl.parent != t || tl.hash > t.hash))
2396 return false;
2397 if (tr != null && (tr.parent != t || tr.hash < t.hash))
2398 return false;
2399 if (t.red && tl != null && tl.red && tr != null && tr.red)
2400 return false;
2401 if (tl != null && !checkInvariants(tl))
2402 return false;
2403 if (tr != null && !checkInvariants(tr))
2404 return false;
2405 return true;
2406 }
2407 }
2408
2409 }