1 /*
2 * Copyright (c) 1997, 2025, 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.ObjectInputStream;
31 import java.io.Serializable;
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 import jdk.internal.access.SharedSecrets;
39
40 /**
41 * Hash table based implementation of the {@code Map} interface. This
42 * implementation provides all of the optional map operations, and permits
43 * {@code null} values and the {@code null} key. (The {@code HashMap}
44 * class is roughly equivalent to {@code Hashtable}, except that it is
45 * unsynchronized and permits nulls.) This class makes no guarantees as to
46 * the order of the map; in particular, it does not guarantee that the order
47 * will remain constant over time.
48 *
49 * <p>This implementation provides constant-time performance for the basic
50 * operations ({@code get} and {@code put}), assuming the hash function
51 * disperses the elements properly among the buckets. Iteration over
52 * collection views requires time proportional to the "capacity" of the
53 * {@code HashMap} instance (the number of buckets) plus its size (the number
54 * of key-value mappings). Thus, it's very important not to set the initial
55 * capacity too high (or the load factor too low) if iteration performance is
56 * important.
57 *
58 * <p>An instance of {@code HashMap} has two parameters that affect its
59 * performance: <i>initial capacity</i> and <i>load factor</i>. The
60 * <i>capacity</i> is the number of buckets in the hash table, and the initial
61 * capacity is simply the capacity at the time the hash table is created. The
62 * <i>load factor</i> is a measure of how full the hash table is allowed to
63 * get before its capacity is automatically increased. When the number of
64 * entries in the hash table exceeds the product of the load factor and the
65 * current capacity, the hash table is <i>rehashed</i> (that is, internal data
66 * structures are rebuilt) so that the hash table has approximately twice the
67 * number of buckets.
68 *
69 * <p>As a general rule, the default load factor (.75) offers a good
70 * tradeoff between time and space costs. Higher values decrease the
71 * space overhead but increase the lookup cost (reflected in most of
72 * the operations of the {@code HashMap} class, including
73 * {@code get} and {@code put}). The expected number of entries in
74 * the map and its load factor should be taken into account when
75 * setting its initial capacity, so as to minimize the number of
76 * rehash operations. If the initial capacity is greater than the
77 * maximum number of entries divided by the load factor, no rehash
78 * operations will ever occur.
79 *
80 * <p>If many mappings are to be stored in a {@code HashMap}
81 * instance, creating it with a sufficiently large capacity will allow
82 * the mappings to be stored more efficiently than letting it perform
83 * automatic rehashing as needed to grow the table. Note that using
84 * many keys with the same {@code hashCode()} is a sure way to slow
85 * down performance of any hash table. To ameliorate impact, when keys
86 * are {@link Comparable}, this class may use comparison order among
87 * keys to help break ties.
88 *
89 * <p><strong>Note that this implementation is not synchronized.</strong>
90 * If multiple threads access a hash map concurrently, and at least one of
91 * the threads modifies the map structurally, it <i>must</i> be
92 * synchronized externally. (A structural modification is any operation
93 * that adds or deletes one or more mappings; merely changing the value
94 * associated with a key that an instance already contains is not a
95 * structural modification.) This is typically accomplished by
96 * synchronizing on some object that naturally encapsulates the map.
97 *
98 * If no such object exists, the map should be "wrapped" using the
99 * {@link Collections#synchronizedMap Collections.synchronizedMap}
100 * method. This is best done at creation time, to prevent accidental
101 * unsynchronized access to the map:<pre>
102 * Map m = Collections.synchronizedMap(new HashMap(...));</pre>
103 *
104 * <p>The iterators returned by all of this class's "collection view methods"
105 * are <i>fail-fast</i>: if the map is structurally modified at any time after
106 * the iterator is created, in any way except through the iterator's own
107 * {@code remove} method, the iterator will throw a
108 * {@link ConcurrentModificationException}. Thus, in the face of concurrent
109 * modification, the iterator fails quickly and cleanly, rather than risking
110 * arbitrary, non-deterministic behavior at an undetermined time in the
111 * future.
112 *
113 * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
114 * as it is, generally speaking, impossible to make any hard guarantees in the
115 * presence of unsynchronized concurrent modification. Fail-fast iterators
116 * throw {@code ConcurrentModificationException} on a best-effort basis.
117 * Therefore, it would be wrong to write a program that depended on this
118 * exception for its correctness: <i>the fail-fast behavior of iterators
119 * should be used only to detect bugs.</i>
120 *
121 * <p>This class is a member of the
122 * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
123 * Java Collections Framework</a>.
124 *
125 * @param <K> the type of keys maintained by this map
126 * @param <V> the type of mapped values
127 *
128 * @author Doug Lea
129 * @author Josh Bloch
130 * @author Arthur van Hoff
131 * @author Neal Gafter
132 * @see Object#hashCode()
133 * @see Collection
134 * @see Map
135 * @see TreeMap
136 * @see Hashtable
137 * @since 1.2
138 */
139 public class HashMap<K,V> extends AbstractMap<K,V>
140 implements Map<K,V>, Cloneable, Serializable {
141
142 @java.io.Serial
143 private static final long serialVersionUID = 362498820763181265L;
144
145 /*
146 * Implementation notes.
147 *
148 * This map usually acts as a binned (bucketed) hash table, but
149 * when bins get too large, they are transformed into bins of
150 * TreeNodes, each structured similarly to those in
151 * java.util.TreeMap. Most methods try to use normal bins, but
152 * relay to TreeNode methods when applicable (simply by checking
153 * instanceof a node). Bins of TreeNodes may be traversed and
154 * used like any others, but additionally support faster lookup
155 * when overpopulated. However, since the vast majority of bins in
156 * normal use are not overpopulated, checking for existence of
157 * tree bins may be delayed in the course of table methods.
158 *
159 * Tree bins (i.e., bins whose elements are all TreeNodes) are
160 * ordered primarily by hashCode, but in the case of ties, if two
161 * elements are of the same "class C implements Comparable<C>",
162 * type then their compareTo method is used for ordering. (We
163 * conservatively check generic types via reflection to validate
164 * this -- see method comparableClassFor). The added complexity
165 * of tree bins is worthwhile in providing worst-case O(log n)
166 * operations when keys either have distinct hashes or are
167 * orderable, Thus, performance degrades gracefully under
168 * accidental or malicious usages in which hashCode() methods
169 * return values that are poorly distributed, as well as those in
170 * which many keys share a hashCode, so long as they are also
171 * Comparable. (If neither of these apply, we may waste about a
172 * factor of two in time and space compared to taking no
173 * precautions. But the only known cases stem from poor user
174 * programming practices that are already so slow that this makes
175 * little difference.)
176 *
177 * Because TreeNodes are about twice the size of regular nodes, we
178 * use them only when bins contain enough nodes to warrant use
179 * (see TREEIFY_THRESHOLD). And when they become too small (due to
180 * removal or resizing) they are converted back to plain bins. In
181 * usages with well-distributed user hashCodes, tree bins are
182 * rarely used. Ideally, under random hashCodes, the frequency of
183 * nodes in bins follows a Poisson distribution
184 * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
185 * parameter of about 0.5 on average for the default resizing
186 * threshold of 0.75, although with a large variance because of
187 * resizing granularity. Ignoring variance, the expected
188 * occurrences of list size k are (exp(-0.5) * pow(0.5, k) /
189 * factorial(k)). The first values are:
190 *
191 * 0: 0.60653066
192 * 1: 0.30326533
193 * 2: 0.07581633
194 * 3: 0.01263606
195 * 4: 0.00157952
196 * 5: 0.00015795
197 * 6: 0.00001316
198 * 7: 0.00000094
199 * 8: 0.00000006
200 * more: less than 1 in ten million
201 *
202 * The root of a tree bin is normally its first node. However,
203 * sometimes (currently only upon Iterator.remove), the root might
204 * be elsewhere, but can be recovered following parent links
205 * (method TreeNode.root()).
206 *
207 * All applicable internal methods accept a hash code as an
208 * argument (as normally supplied from a public method), allowing
209 * them to call each other without recomputing user hashCodes.
210 * Most internal methods also accept a "tab" argument, that is
211 * normally the current table, but may be a new or old one when
212 * resizing or converting.
213 *
214 * When bin lists are treeified, split, or untreeified, we keep
215 * them in the same relative access/traversal order (i.e., field
216 * Node.next) to better preserve locality, and to slightly
217 * simplify handling of splits and traversals that invoke
218 * iterator.remove. When using comparators on insertion, to keep a
219 * total ordering (or as close as is required here) across
220 * rebalancings, we compare classes and identityHashCodes as
221 * tie-breakers.
222 *
223 * The use and transitions among plain vs tree modes is
224 * complicated by the existence of subclass LinkedHashMap. See
225 * below for hook methods defined to be invoked upon insertion,
226 * removal and access that allow LinkedHashMap internals to
227 * otherwise remain independent of these mechanics. (This also
228 * requires that a map instance be passed to some utility methods
229 * that may create new nodes.)
230 *
231 * The concurrent-programming-like SSA-based coding style helps
232 * avoid aliasing errors amid all of the twisty pointer operations.
233 */
234
235 /**
236 * The default initial capacity - MUST be a power of two.
237 */
238 static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16
239
240 /**
241 * The maximum capacity, used if a higher value is implicitly specified
242 * by either of the constructors with arguments.
243 * MUST be a power of two <= 1<<30.
244 */
245 static final int MAXIMUM_CAPACITY = 1 << 30;
246
247 /**
248 * The load factor used when none specified in constructor.
249 */
250 static final float DEFAULT_LOAD_FACTOR = 0.75f;
251
252 /**
253 * The bin count threshold for using a tree rather than list for a
254 * bin. Bins are converted to trees when adding an element to a
255 * bin with at least this many nodes. The value must be greater
256 * than 2 and should be at least 8 to mesh with assumptions in
257 * tree removal about conversion back to plain bins upon
258 * shrinkage.
259 */
260 static final int TREEIFY_THRESHOLD = 8;
261
262 /**
263 * The bin count threshold for untreeifying a (split) bin during a
264 * resize operation. Should be less than TREEIFY_THRESHOLD, and at
265 * most 6 to mesh with shrinkage detection under removal.
266 */
267 static final int UNTREEIFY_THRESHOLD = 6;
268
269 /**
270 * The smallest table capacity for which bins may be treeified.
271 * (Otherwise the table is resized if too many nodes in a bin.)
272 * Should be at least 4 * TREEIFY_THRESHOLD to avoid conflicts
273 * between resizing and treeification thresholds.
274 */
275 static final int MIN_TREEIFY_CAPACITY = 64;
276
277 /**
278 * Basic hash bin node, used for most entries. (See below for
279 * TreeNode subclass, and in LinkedHashMap for its Entry subclass.)
280 */
281 static class Node<K,V> implements Map.Entry<K,V> {
282 final int hash;
283 final K key;
284 V value;
285 Node<K,V> next;
286
287 Node(int hash, K key, V value, Node<K,V> next) {
288 this.hash = hash;
289 this.key = key;
290 this.value = value;
291 this.next = next;
292 }
293
294 public final K getKey() { return key; }
295 public final V getValue() { return value; }
296 public final String toString() { return key + "=" + value; }
297
298 public final int hashCode() {
299 return Objects.hashCode(key) ^ Objects.hashCode(value);
300 }
301
302 public final V setValue(V newValue) {
303 V oldValue = value;
304 value = newValue;
305 return oldValue;
306 }
307
308 public final boolean equals(Object o) {
309 if (o == this)
310 return true;
311
312 return o instanceof Map.Entry<?, ?> e
313 && Objects.equals(key, e.getKey())
314 && Objects.equals(value, e.getValue());
315 }
316 }
317
318 /* ---------------- Static utilities -------------- */
319
320 /**
321 * Computes key.hashCode() and spreads (XORs) higher bits of hash
322 * to lower. Because the table uses power-of-two masking, sets of
323 * hashes that vary only in bits above the current mask will
324 * always collide. (Among known examples are sets of Float keys
325 * holding consecutive whole numbers in small tables.) So we
326 * apply a transform that spreads the impact of higher bits
327 * downward. There is a tradeoff between speed, utility, and
328 * quality of bit-spreading. Because many common sets of hashes
329 * are already reasonably distributed (so don't benefit from
330 * spreading), and because we use trees to handle large sets of
331 * collisions in bins, we just XOR some shifted bits in the
332 * cheapest possible way to reduce systematic lossage, as well as
333 * to incorporate impact of the highest bits that would otherwise
334 * never be used in index calculations because of table bounds.
335 */
336 static final int hash(Object key) {
337 int h;
338 return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
339 }
340
341 /**
342 * Returns x's Class if it is of the form "class C implements
343 * Comparable<C>", else null.
344 */
345 static Class<?> comparableClassFor(Object x) {
346 if (x instanceof Comparable) {
347 Class<?> c; Type[] ts, as; ParameterizedType p;
348 if ((c = x.getClass()) == String.class) // bypass checks
349 return c;
350 if ((ts = c.getGenericInterfaces()) != null) {
351 for (Type t : ts) {
352 if ((t instanceof ParameterizedType) &&
353 ((p = (ParameterizedType) t).getRawType() ==
354 Comparable.class) &&
355 (as = p.getActualTypeArguments()) != null &&
356 as.length == 1 && as[0] == c) // type arg is c
357 return c;
358 }
359 }
360 }
361 return null;
362 }
363
364 /**
365 * Returns k.compareTo(x) if x matches kc (k's screened comparable
366 * class), else 0.
367 */
368 @SuppressWarnings("unchecked") // for cast to Comparable
369 static int compareComparables(Class<?> kc, Object k, Object x) {
370 return (x == null || x.getClass() != kc ? 0 :
371 ((Comparable)k).compareTo(x));
372 }
373
374 /**
375 * Returns a power of two size for the given target capacity.
376 */
377 static final int tableSizeFor(int cap) {
378 int n = -1 >>> Integer.numberOfLeadingZeros(cap - 1);
379 return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
380 }
381
382 /* ---------------- Fields -------------- */
383
384 /**
385 * The table, initialized on first use, and resized as
386 * necessary. When allocated, length is always a power of two.
387 * (We also tolerate length zero in some operations to allow
388 * bootstrapping mechanics that are currently not needed.)
389 */
390 transient Node<K,V>[] table;
391
392 /**
393 * Holds cached entrySet(). Note that AbstractMap fields are used
394 * for keySet() and values().
395 */
396 transient Set<Map.Entry<K,V>> entrySet;
397
398 /**
399 * The number of key-value mappings contained in this map.
400 */
401 transient int size;
402
403 /**
404 * The number of times this HashMap has been structurally modified
405 * Structural modifications are those that change the number of mappings in
406 * the HashMap or otherwise modify its internal structure (e.g.,
407 * rehash). This field is used to make iterators on Collection-views of
408 * the HashMap fail-fast. (See ConcurrentModificationException).
409 */
410 transient int modCount;
411
412 /**
413 * The next size value at which to resize (capacity * load factor).
414 *
415 * @serial
416 */
417 // (The javadoc description is true upon serialization.
418 // Additionally, if the table array has not been allocated, this
419 // field holds the initial array capacity, or zero signifying
420 // DEFAULT_INITIAL_CAPACITY.)
421 int threshold;
422
423 /**
424 * The load factor for the hash table.
425 *
426 * @serial
427 */
428 final float loadFactor;
429
430 /* ---------------- Public operations -------------- */
431
432 /**
433 * Constructs an empty {@code HashMap} with the specified initial
434 * capacity and load factor.
435 *
436 * @apiNote
437 * To create a {@code HashMap} with an initial capacity that accommodates
438 * an expected number of mappings, use {@link #newHashMap(int) newHashMap}.
439 *
440 * @param initialCapacity the initial capacity
441 * @param loadFactor the load factor
442 * @throws IllegalArgumentException if the initial capacity is negative
443 * or the load factor is nonpositive
444 */
445 public HashMap(int initialCapacity, float loadFactor) {
446 if (initialCapacity < 0)
447 throw new IllegalArgumentException("Illegal initial capacity: " +
448 initialCapacity);
449 if (initialCapacity > MAXIMUM_CAPACITY)
450 initialCapacity = MAXIMUM_CAPACITY;
451 if (loadFactor <= 0 || Float.isNaN(loadFactor))
452 throw new IllegalArgumentException("Illegal load factor: " +
453 loadFactor);
454 this.loadFactor = loadFactor;
455 this.threshold = tableSizeFor(initialCapacity);
456 }
457
458 /**
459 * Constructs an empty {@code HashMap} with the specified initial
460 * capacity and the default load factor (0.75).
461 *
462 * @apiNote
463 * To create a {@code HashMap} with an initial capacity that accommodates
464 * an expected number of mappings, use {@link #newHashMap(int) newHashMap}.
465 *
466 * @param initialCapacity the initial capacity.
467 * @throws IllegalArgumentException if the initial capacity is negative.
468 */
469 public HashMap(int initialCapacity) {
470 this(initialCapacity, DEFAULT_LOAD_FACTOR);
471 }
472
473 /**
474 * Constructs an empty {@code HashMap} with the default initial capacity
475 * (16) and the default load factor (0.75).
476 */
477 public HashMap() {
478 this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
479 }
480
481 /**
482 * Constructs a new {@code HashMap} with the same mappings as the
483 * specified {@code Map}. The {@code HashMap} is created with
484 * default load factor (0.75) and an initial capacity sufficient to
485 * hold the mappings in the specified {@code Map}.
486 *
487 * @param m the map whose mappings are to be placed in this map
488 * @throws NullPointerException if the specified map is null
489 */
490 @SuppressWarnings("this-escape")
491 public HashMap(Map<? extends K, ? extends V> m) {
492 this.loadFactor = DEFAULT_LOAD_FACTOR;
493 putMapEntries(m, false);
494 }
495
496 /**
497 * Implements Map.putAll and Map constructor.
498 *
499 * @param m the map
500 * @param evict false when initially constructing this map, else
501 * true (relayed to method afterNodeInsertion).
502 */
503 final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
504 int s = m.size();
505 if (s > 0) {
506 if (table == null) { // pre-size
507 double dt = Math.ceil(s / (double)loadFactor);
508 int t = ((dt < (double)MAXIMUM_CAPACITY) ?
509 (int)dt : MAXIMUM_CAPACITY);
510 if (t > threshold)
511 threshold = tableSizeFor(t);
512 } else {
513 // Because of linked-list bucket constraints, we cannot
514 // expand all at once, but can reduce total resize
515 // effort by repeated doubling now vs later
516 while (s > threshold && table.length < MAXIMUM_CAPACITY)
517 resize();
518 }
519
520 for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
521 K key = e.getKey();
522 V value = e.getValue();
523 putVal(hash(key), key, value, false, evict);
524 }
525 }
526 }
527
528 /**
529 * Returns the number of key-value mappings in this map.
530 *
531 * @return the number of key-value mappings in this map
532 */
533 public int size() {
534 return size;
535 }
536
537 /**
538 * Returns {@code true} if this map contains no key-value mappings.
539 *
540 * @return {@code true} if this map contains no key-value mappings
541 */
542 public boolean isEmpty() {
543 return size == 0;
544 }
545
546 /**
547 * Returns the value to which the specified key is mapped,
548 * or {@code null} if this map contains no mapping for the key.
549 *
550 * <p>More formally, if this map contains a mapping from a key
551 * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
552 * key.equals(k))}, then this method returns {@code v}; otherwise
553 * it returns {@code null}. (There can be at most one such mapping.)
554 *
555 * <p>A return value of {@code null} does not <i>necessarily</i>
556 * indicate that the map contains no mapping for the key; it's also
557 * possible that the map explicitly maps the key to {@code null}.
558 * The {@link #containsKey containsKey} operation may be used to
559 * distinguish these two cases.
560 *
561 * @see #put(Object, Object)
562 */
563 public V get(Object key) {
564 Node<K,V> e;
565 return (e = getNode(key)) == null ? null : e.value;
566 }
567
568 /**
569 * Implements Map.get and related methods.
570 *
571 * @param key the key
572 * @return the node, or null if none
573 */
574 final Node<K,V> getNode(Object key) {
575 Node<K,V>[] tab; Node<K,V> first, e; int n, hash; K k;
576 if ((tab = table) != null && (n = tab.length) > 0 &&
577 (first = tab[(n - 1) & (hash = hash(key))]) != null) {
578 if (first.hash == hash && // always check first node
579 Objects.equals(key, first.key))
580 return first;
581 if ((e = first.next) != null) {
582 if (first instanceof TreeNode)
583 return ((TreeNode<K,V>)first).getTreeNode(hash, key);
584 do {
585 if (e.hash == hash &&
586 Objects.equals(key, e.key))
587 return e;
588 } while ((e = e.next) != null);
589 }
590 }
591 return null;
592 }
593
594 /**
595 * Returns {@code true} if this map contains a mapping for the
596 * specified key.
597 *
598 * @param key The key whose presence in this map is to be tested
599 * @return {@code true} if this map contains a mapping for the specified
600 * key.
601 */
602 public boolean containsKey(Object key) {
603 return getNode(key) != null;
604 }
605
606 /**
607 * Associates the specified value with the specified key in this map.
608 * If the map previously contained a mapping for the key, the old
609 * value is replaced.
610 *
611 * @param key key with which the specified value is to be associated
612 * @param value value to be associated with the specified key
613 * @return the previous value associated with {@code key}, or
614 * {@code null} if there was no mapping for {@code key}.
615 * (A {@code null} return can also indicate that the map
616 * previously associated {@code null} with {@code key}.)
617 */
618 public V put(K key, V value) {
619 return putVal(hash(key), key, value, false, true);
620 }
621
622 /**
623 * Implements Map.put and related methods.
624 *
625 * @param hash hash for key
626 * @param key the key
627 * @param value the value to put
628 * @param onlyIfAbsent if true, don't change existing value
629 * @param evict if false, the table is in creation mode.
630 * @return previous value, or null if none
631 */
632 final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
633 boolean evict) {
634 Node<K,V>[] tab; Node<K,V> p; int n, i;
635 if ((tab = table) == null || (n = tab.length) == 0)
636 n = (tab = resize()).length;
637 if ((p = tab[i = (n - 1) & hash]) == null)
638 tab[i] = newNode(hash, key, value, null);
639 else {
640 Node<K,V> e; K k;
641 if (p.hash == hash &&
642 Objects.equals(key, p.key))
643 e = p;
644 else if (p instanceof TreeNode)
645 e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
646 else {
647 for (int binCount = 0; ; ++binCount) {
648 if ((e = p.next) == null) {
649 p.next = newNode(hash, key, value, null);
650 if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
651 treeifyBin(tab, hash);
652 break;
653 }
654 if (e.hash == hash &&
655 Objects.equals(key, e.key))
656 break;
657 p = e;
658 }
659 }
660 if (e != null) { // existing mapping for key
661 V oldValue = e.value;
662 if (!onlyIfAbsent || oldValue == null)
663 e.value = value;
664 afterNodeAccess(e);
665 return oldValue;
666 }
667 }
668 ++modCount;
669 if (++size > threshold)
670 resize();
671 afterNodeInsertion(evict);
672 return null;
673 }
674
675 /**
676 * Initializes or doubles table size. If null, allocates in
677 * accord with initial capacity target held in field threshold.
678 * Otherwise, because we are using power-of-two expansion, the
679 * elements from each bin must either stay at same index, or move
680 * with a power of two offset in the new table.
681 *
682 * @return the table
683 */
684 final Node<K,V>[] resize() {
685 Node<K,V>[] oldTab = table;
686 int oldCap = (oldTab == null) ? 0 : oldTab.length;
687 int oldThr = threshold;
688 int newCap, newThr = 0;
689 if (oldCap > 0) {
690 if (oldCap >= MAXIMUM_CAPACITY) {
691 threshold = Integer.MAX_VALUE;
692 return oldTab;
693 }
694 else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
695 oldCap >= DEFAULT_INITIAL_CAPACITY)
696 newThr = oldThr << 1; // double threshold
697 }
698 else if (oldThr > 0) // initial capacity was placed in threshold
699 newCap = oldThr;
700 else { // zero initial threshold signifies using defaults
701 newCap = DEFAULT_INITIAL_CAPACITY;
702 newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
703 }
704 if (newThr == 0) {
705 float ft = (float)newCap * loadFactor;
706 newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
707 (int)ft : Integer.MAX_VALUE);
708 }
709 threshold = newThr;
710 @SuppressWarnings({"rawtypes","unchecked"})
711 Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
712 table = newTab;
713 if (oldTab != null) {
714 for (int j = 0; j < oldCap; ++j) {
715 Node<K,V> e;
716 if ((e = oldTab[j]) != null) {
717 oldTab[j] = null;
718 if (e.next == null)
719 newTab[e.hash & (newCap - 1)] = e;
720 else if (e instanceof TreeNode)
721 ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
722 else { // preserve order
723 Node<K,V> loHead = null, loTail = null;
724 Node<K,V> hiHead = null, hiTail = null;
725 Node<K,V> next;
726 do {
727 next = e.next;
728 if ((e.hash & oldCap) == 0) {
729 if (loTail == null)
730 loHead = e;
731 else
732 loTail.next = e;
733 loTail = e;
734 }
735 else {
736 if (hiTail == null)
737 hiHead = e;
738 else
739 hiTail.next = e;
740 hiTail = e;
741 }
742 } while ((e = next) != null);
743 if (loTail != null) {
744 loTail.next = null;
745 newTab[j] = loHead;
746 }
747 if (hiTail != null) {
748 hiTail.next = null;
749 newTab[j + oldCap] = hiHead;
750 }
751 }
752 }
753 }
754 }
755 return newTab;
756 }
757
758 /**
759 * Replaces all linked nodes in bin at index for given hash unless
760 * table is too small, in which case resizes instead.
761 */
762 final void treeifyBin(Node<K,V>[] tab, int hash) {
763 int n, index; Node<K,V> e;
764 if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
765 resize();
766 else if ((e = tab[index = (n - 1) & hash]) != null) {
767 TreeNode<K,V> hd = null, tl = null;
768 do {
769 TreeNode<K,V> p = replacementTreeNode(e, null);
770 if (tl == null)
771 hd = p;
772 else {
773 p.prev = tl;
774 tl.next = p;
775 }
776 tl = p;
777 } while ((e = e.next) != null);
778 if ((tab[index] = hd) != null)
779 hd.treeify(tab);
780 }
781 }
782
783 /**
784 * Copies all of the mappings from the specified map to this map.
785 * These mappings will replace any mappings that this map had for
786 * any of the keys currently in the specified map.
787 *
788 * @param m mappings to be stored in this map
789 * @throws NullPointerException if the specified map is null
790 */
791 public void putAll(Map<? extends K, ? extends V> m) {
792 putMapEntries(m, true);
793 }
794
795 /**
796 * Removes the mapping for the specified key from this map if present.
797 *
798 * @param key key whose mapping is to be removed from the map
799 * @return the previous value associated with {@code key}, or
800 * {@code null} if there was no mapping for {@code key}.
801 * (A {@code null} return can also indicate that the map
802 * previously associated {@code null} with {@code key}.)
803 */
804 public V remove(Object key) {
805 Node<K,V> e;
806 return (e = removeNode(hash(key), key, null, false, true)) == null ?
807 null : e.value;
808 }
809
810 /**
811 * Implements Map.remove and related methods.
812 *
813 * @param hash hash for key
814 * @param key the key
815 * @param value the value to match if matchValue, else ignored
816 * @param matchValue if true only remove if value is equal
817 * @param movable if false do not move other nodes while removing
818 * @return the node, or null if none
819 */
820 final Node<K,V> removeNode(int hash, Object key, Object value,
821 boolean matchValue, boolean movable) {
822 Node<K,V>[] tab; Node<K,V> p; int n, index;
823 if ((tab = table) != null && (n = tab.length) > 0 &&
824 (p = tab[index = (n - 1) & hash]) != null) {
825 Node<K,V> node = null, e; K k; V v;
826 if (p.hash == hash &&
827 Objects.equals(key, p.key))
828 node = p;
829 else if ((e = p.next) != null) {
830 if (p instanceof TreeNode)
831 node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
832 else {
833 do {
834 if (e.hash == hash &&
835 Objects.equals(key, e.key)) {
836 node = e;
837 break;
838 }
839 p = e;
840 } while ((e = e.next) != null);
841 }
842 }
843 if (node != null && (!matchValue || (v = node.value) == value ||
844 (value != null && value.equals(v)))) {
845 if (node instanceof TreeNode)
846 ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
847 else if (node == p)
848 tab[index] = node.next;
849 else
850 p.next = node.next;
851 ++modCount;
852 --size;
853 afterNodeRemoval(node);
854 return node;
855 }
856 }
857 return null;
858 }
859
860 /**
861 * Removes all of the mappings from this map.
862 * The map will be empty after this call returns.
863 */
864 public void clear() {
865 Node<K,V>[] tab;
866 modCount++;
867 if ((tab = table) != null && size > 0) {
868 size = 0;
869 for (int i = 0; i < tab.length; ++i)
870 tab[i] = null;
871 }
872 }
873
874 /**
875 * Returns {@code true} if this map maps one or more keys to the
876 * specified value.
877 *
878 * @param value value whose presence in this map is to be tested
879 * @return {@code true} if this map maps one or more keys to the
880 * specified value
881 */
882 public boolean containsValue(Object value) {
883 Node<K,V>[] tab; V v;
884 if ((tab = table) != null && size > 0) {
885 for (Node<K,V> e : tab) {
886 for (; e != null; e = e.next) {
887 if ((v = e.value) == value ||
888 (value != null && value.equals(v)))
889 return true;
890 }
891 }
892 }
893 return false;
894 }
895
896 /**
897 * Returns a {@link Set} view of the keys contained in this map.
898 * The set is backed by the map, so changes to the map are
899 * reflected in the set, and vice-versa. If the map is modified
900 * while an iteration over the set is in progress (except through
901 * the iterator's own {@code remove} operation), the results of
902 * the iteration are undefined. The set supports element removal,
903 * which removes the corresponding mapping from the map, via the
904 * {@code Iterator.remove}, {@code Set.remove},
905 * {@code removeAll}, {@code retainAll}, and {@code clear}
906 * operations. It does not support the {@code add} or {@code addAll}
907 * operations.
908 *
909 * @return a set view of the keys contained in this map
910 */
911 public Set<K> keySet() {
912 Set<K> ks = keySet;
913 if (ks == null) {
914 ks = new KeySet();
915 keySet = ks;
916 }
917 return ks;
918 }
919
920 /**
921 * Prepares the array for {@link Collection#toArray(Object[])} implementation.
922 * If supplied array is smaller than this map size, a new array is allocated.
923 * If supplied array is bigger than this map size, a null is written at size index.
924 *
925 * @param a an original array passed to {@code toArray()} method
926 * @param <T> type of array elements
927 * @return an array ready to be filled and returned from {@code toArray()} method.
928 */
929 @SuppressWarnings("unchecked")
930 final <T> T[] prepareArray(T[] a) {
931 int size = this.size;
932 if (a.length < size) {
933 return (T[]) java.lang.reflect.Array
934 .newInstance(a.getClass().getComponentType(), size);
935 }
936 if (a.length > size) {
937 a[size] = null;
938 }
939 return a;
940 }
941
942 /**
943 * Fills an array with this map keys and returns it. This method assumes
944 * that input array is big enough to fit all the keys. Use
945 * {@link #prepareArray(Object[])} to ensure this.
946 *
947 * @param a an array to fill
948 * @param <T> type of array elements
949 * @return supplied array
950 */
951 <T> T[] keysToArray(T[] a) {
952 Object[] r = a;
953 Node<K,V>[] tab;
954 int idx = 0;
955 if (size > 0 && (tab = table) != null) {
956 for (Node<K,V> e : tab) {
957 for (; e != null; e = e.next) {
958 r[idx++] = e.key;
959 }
960 }
961 }
962 return a;
963 }
964
965 /**
966 * Fills an array with this map values and returns it. This method assumes
967 * that input array is big enough to fit all the values. Use
968 * {@link #prepareArray(Object[])} to ensure this.
969 *
970 * @param a an array to fill
971 * @param <T> type of array elements
972 * @return supplied array
973 */
974 <T> T[] valuesToArray(T[] a) {
975 Object[] r = a;
976 Node<K,V>[] tab;
977 int idx = 0;
978 if (size > 0 && (tab = table) != null) {
979 for (Node<K,V> e : tab) {
980 for (; e != null; e = e.next) {
981 r[idx++] = e.value;
982 }
983 }
984 }
985 return a;
986 }
987
988 final class KeySet extends AbstractSet<K> {
989 public final int size() { return size; }
990 public final void clear() { HashMap.this.clear(); }
991 public final Iterator<K> iterator() { return new KeyIterator(); }
992 public final boolean contains(Object o) { return containsKey(o); }
993 public final boolean remove(Object key) {
994 return removeNode(hash(key), key, null, false, true) != null;
995 }
996 public final Spliterator<K> spliterator() {
997 return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
998 }
999
1000 public Object[] toArray() {
1001 return keysToArray(new Object[size]);
1002 }
1003
1004 public <T> T[] toArray(T[] a) {
1005 return keysToArray(prepareArray(a));
1006 }
1007
1008 public final void forEach(Consumer<? super K> action) {
1009 Node<K,V>[] tab;
1010 if (action == null)
1011 throw new NullPointerException();
1012 if (size > 0 && (tab = table) != null) {
1013 int mc = modCount;
1014 for (Node<K,V> e : tab) {
1015 for (; e != null; e = e.next)
1016 action.accept(e.key);
1017 }
1018 if (modCount != mc)
1019 throw new ConcurrentModificationException();
1020 }
1021 }
1022 }
1023
1024 /**
1025 * Returns a {@link Collection} view of the values contained in this map.
1026 * The collection is backed by the map, so changes to the map are
1027 * reflected in the collection, and vice-versa. If the map is
1028 * modified while an iteration over the collection is in progress
1029 * (except through the iterator's own {@code remove} operation),
1030 * the results of the iteration are undefined. The collection
1031 * supports element removal, which removes the corresponding
1032 * mapping from the map, via the {@code Iterator.remove},
1033 * {@code Collection.remove}, {@code removeAll},
1034 * {@code retainAll} and {@code clear} operations. It does not
1035 * support the {@code add} or {@code addAll} operations.
1036 *
1037 * @return a view of the values contained in this map
1038 */
1039 public Collection<V> values() {
1040 Collection<V> vs = values;
1041 if (vs == null) {
1042 vs = new Values();
1043 values = vs;
1044 }
1045 return vs;
1046 }
1047
1048 final class Values extends AbstractCollection<V> {
1049 public final int size() { return size; }
1050 public final void clear() { HashMap.this.clear(); }
1051 public final Iterator<V> iterator() { return new ValueIterator(); }
1052 public final boolean contains(Object o) { return containsValue(o); }
1053 public final Spliterator<V> spliterator() {
1054 return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
1055 }
1056
1057 public Object[] toArray() {
1058 return valuesToArray(new Object[size]);
1059 }
1060
1061 public <T> T[] toArray(T[] a) {
1062 return valuesToArray(prepareArray(a));
1063 }
1064
1065 public final void forEach(Consumer<? super V> action) {
1066 Node<K,V>[] tab;
1067 if (action == null)
1068 throw new NullPointerException();
1069 if (size > 0 && (tab = table) != null) {
1070 int mc = modCount;
1071 for (Node<K,V> e : tab) {
1072 for (; e != null; e = e.next)
1073 action.accept(e.value);
1074 }
1075 if (modCount != mc)
1076 throw new ConcurrentModificationException();
1077 }
1078 }
1079 }
1080
1081 /**
1082 * Returns a {@link Set} view of the mappings contained in this map.
1083 * The set is backed by the map, so changes to the map are
1084 * reflected in the set, and vice-versa. If the map is modified
1085 * while an iteration over the set is in progress (except through
1086 * the iterator's own {@code remove} operation, or through the
1087 * {@code setValue} operation on a map entry returned by the
1088 * iterator) the results of the iteration are undefined. The set
1089 * supports element removal, which removes the corresponding
1090 * mapping from the map, via the {@code Iterator.remove},
1091 * {@code Set.remove}, {@code removeAll}, {@code retainAll} and
1092 * {@code clear} operations. It does not support the
1093 * {@code add} or {@code addAll} operations.
1094 *
1095 * @return a set view of the mappings contained in this map
1096 */
1097 public Set<Map.Entry<K,V>> entrySet() {
1098 Set<Map.Entry<K,V>> es;
1099 return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
1100 }
1101
1102 final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
1103 public final int size() { return size; }
1104 public final void clear() { HashMap.this.clear(); }
1105 public final Iterator<Map.Entry<K,V>> iterator() {
1106 return new EntryIterator();
1107 }
1108 public final boolean contains(Object o) {
1109 if (!(o instanceof Map.Entry<?, ?> e))
1110 return false;
1111 Object key = e.getKey();
1112 Node<K,V> candidate = getNode(key);
1113 return candidate != null && candidate.equals(e);
1114 }
1115 public final boolean remove(Object o) {
1116 if (o instanceof Map.Entry<?, ?> e) {
1117 Object key = e.getKey();
1118 Object value = e.getValue();
1119 return removeNode(hash(key), key, value, true, true) != null;
1120 }
1121 return false;
1122 }
1123 public final Spliterator<Map.Entry<K,V>> spliterator() {
1124 return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
1125 }
1126 public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
1127 Node<K,V>[] tab;
1128 if (action == null)
1129 throw new NullPointerException();
1130 if (size > 0 && (tab = table) != null) {
1131 int mc = modCount;
1132 for (Node<K,V> e : tab) {
1133 for (; e != null; e = e.next)
1134 action.accept(e);
1135 }
1136 if (modCount != mc)
1137 throw new ConcurrentModificationException();
1138 }
1139 }
1140 }
1141
1142 // Overrides of JDK8 Map extension methods
1143
1144 @Override
1145 public V getOrDefault(Object key, V defaultValue) {
1146 Node<K,V> e;
1147 return (e = getNode(key)) == null ? defaultValue : e.value;
1148 }
1149
1150 @Override
1151 public V putIfAbsent(K key, V value) {
1152 return putVal(hash(key), key, value, true, true);
1153 }
1154
1155 @Override
1156 public boolean remove(Object key, Object value) {
1157 return removeNode(hash(key), key, value, true, true) != null;
1158 }
1159
1160 @Override
1161 public boolean replace(K key, V oldValue, V newValue) {
1162 Node<K,V> e; V v;
1163 if ((e = getNode(key)) != null &&
1164 ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
1165 e.value = newValue;
1166 afterNodeAccess(e);
1167 return true;
1168 }
1169 return false;
1170 }
1171
1172 @Override
1173 public V replace(K key, V value) {
1174 Node<K,V> e;
1175 if ((e = getNode(key)) != null) {
1176 V oldValue = e.value;
1177 e.value = value;
1178 afterNodeAccess(e);
1179 return oldValue;
1180 }
1181 return null;
1182 }
1183
1184 /**
1185 * {@inheritDoc}
1186 *
1187 * <p>This method will, on a best-effort basis, throw a
1188 * {@link ConcurrentModificationException} if it is detected that the
1189 * mapping function modifies this map during computation.
1190 *
1191 * @throws ConcurrentModificationException if it is detected that the
1192 * mapping function modified this map
1193 */
1194 @Override
1195 public V computeIfAbsent(K key,
1196 Function<? super K, ? extends V> mappingFunction) {
1197 if (mappingFunction == null)
1198 throw new NullPointerException();
1199 int hash = hash(key);
1200 Node<K,V>[] tab; Node<K,V> first; int n, i;
1201 int binCount = 0;
1202 TreeNode<K,V> t = null;
1203 Node<K,V> old = null;
1204 if (size > threshold || (tab = table) == null ||
1205 (n = tab.length) == 0)
1206 n = (tab = resize()).length;
1207 if ((first = tab[i = (n - 1) & hash]) != null) {
1208 if (first instanceof TreeNode)
1209 old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
1210 else {
1211 Node<K,V> e = first; K k;
1212 do {
1213 if (e.hash == hash &&
1214 Objects.equals(key, e.key)) {
1215 old = e;
1216 break;
1217 }
1218 ++binCount;
1219 } while ((e = e.next) != null);
1220 }
1221 V oldValue;
1222 if (old != null && (oldValue = old.value) != null) {
1223 afterNodeAccess(old);
1224 return oldValue;
1225 }
1226 }
1227 int mc = modCount;
1228 V v = mappingFunction.apply(key);
1229 if (mc != modCount) { throw new ConcurrentModificationException(); }
1230 if (v == null) {
1231 return null;
1232 } else if (old != null) {
1233 old.value = v;
1234 afterNodeAccess(old);
1235 return v;
1236 }
1237 else if (t != null)
1238 t.putTreeVal(this, tab, hash, key, v);
1239 else {
1240 tab[i] = newNode(hash, key, v, first);
1241 if (binCount >= TREEIFY_THRESHOLD - 1)
1242 treeifyBin(tab, hash);
1243 }
1244 modCount = mc + 1;
1245 ++size;
1246 afterNodeInsertion(true);
1247 return v;
1248 }
1249
1250 /**
1251 * {@inheritDoc}
1252 *
1253 * <p>This method will, on a best-effort basis, throw a
1254 * {@link ConcurrentModificationException} if it is detected that the
1255 * remapping function modifies this map during computation.
1256 *
1257 * @throws ConcurrentModificationException if it is detected that the
1258 * remapping function modified this map
1259 */
1260 @Override
1261 public V computeIfPresent(K key,
1262 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1263 if (remappingFunction == null)
1264 throw new NullPointerException();
1265 Node<K,V> e; V oldValue;
1266 if ((e = getNode(key)) != null &&
1267 (oldValue = e.value) != null) {
1268 int mc = modCount;
1269 V v = remappingFunction.apply(key, oldValue);
1270 if (mc != modCount) { throw new ConcurrentModificationException(); }
1271 if (v != null) {
1272 e.value = v;
1273 afterNodeAccess(e);
1274 return v;
1275 }
1276 else {
1277 int hash = hash(key);
1278 removeNode(hash, key, null, false, true);
1279 }
1280 }
1281 return null;
1282 }
1283
1284 /**
1285 * {@inheritDoc}
1286 *
1287 * <p>This method will, on a best-effort basis, throw a
1288 * {@link ConcurrentModificationException} if it is detected that the
1289 * remapping function modifies this map during computation.
1290 *
1291 * @throws ConcurrentModificationException if it is detected that the
1292 * remapping function modified this map
1293 */
1294 @Override
1295 public V compute(K key,
1296 BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1297 if (remappingFunction == null)
1298 throw new NullPointerException();
1299 int hash = hash(key);
1300 Node<K,V>[] tab; Node<K,V> first; int n, i;
1301 int binCount = 0;
1302 TreeNode<K,V> t = null;
1303 Node<K,V> old = null;
1304 if (size > threshold || (tab = table) == null ||
1305 (n = tab.length) == 0)
1306 n = (tab = resize()).length;
1307 if ((first = tab[i = (n - 1) & hash]) != null) {
1308 if (first instanceof TreeNode)
1309 old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
1310 else {
1311 Node<K,V> e = first; K k;
1312 do {
1313 if (e.hash == hash &&
1314 Objects.equals(key, e.key)) {
1315 old = e;
1316 break;
1317 }
1318 ++binCount;
1319 } while ((e = e.next) != null);
1320 }
1321 }
1322 V oldValue = (old == null) ? null : old.value;
1323 int mc = modCount;
1324 V v = remappingFunction.apply(key, oldValue);
1325 if (mc != modCount) { throw new ConcurrentModificationException(); }
1326 if (old != null) {
1327 if (v != null) {
1328 old.value = v;
1329 afterNodeAccess(old);
1330 }
1331 else
1332 removeNode(hash, key, null, false, true);
1333 }
1334 else if (v != null) {
1335 if (t != null)
1336 t.putTreeVal(this, tab, hash, key, v);
1337 else {
1338 tab[i] = newNode(hash, key, v, first);
1339 if (binCount >= TREEIFY_THRESHOLD - 1)
1340 treeifyBin(tab, hash);
1341 }
1342 modCount = mc + 1;
1343 ++size;
1344 afterNodeInsertion(true);
1345 }
1346 return v;
1347 }
1348
1349 /**
1350 * {@inheritDoc}
1351 *
1352 * <p>This method will, on a best-effort basis, throw a
1353 * {@link ConcurrentModificationException} if it is detected that the
1354 * remapping function modifies this map during computation.
1355 *
1356 * @throws ConcurrentModificationException if it is detected that the
1357 * remapping function modified this map
1358 */
1359 @Override
1360 public V merge(K key, V value,
1361 BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1362 if (value == null || remappingFunction == null)
1363 throw new NullPointerException();
1364 int hash = hash(key);
1365 Node<K,V>[] tab; Node<K,V> first; int n, i;
1366 int binCount = 0;
1367 TreeNode<K,V> t = null;
1368 Node<K,V> old = null;
1369 if (size > threshold || (tab = table) == null ||
1370 (n = tab.length) == 0)
1371 n = (tab = resize()).length;
1372 if ((first = tab[i = (n - 1) & hash]) != null) {
1373 if (first instanceof TreeNode)
1374 old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
1375 else {
1376 Node<K,V> e = first; K k;
1377 do {
1378 if (e.hash == hash &&
1379 Objects.equals(key, e.key)) {
1380 old = e;
1381 break;
1382 }
1383 ++binCount;
1384 } while ((e = e.next) != null);
1385 }
1386 }
1387 if (old != null) {
1388 V v;
1389 if (old.value != null) {
1390 int mc = modCount;
1391 v = remappingFunction.apply(old.value, value);
1392 if (mc != modCount) {
1393 throw new ConcurrentModificationException();
1394 }
1395 } else {
1396 v = value;
1397 }
1398 if (v != null) {
1399 old.value = v;
1400 afterNodeAccess(old);
1401 }
1402 else
1403 removeNode(hash, key, null, false, true);
1404 return v;
1405 } else {
1406 if (t != null)
1407 t.putTreeVal(this, tab, hash, key, value);
1408 else {
1409 tab[i] = newNode(hash, key, value, first);
1410 if (binCount >= TREEIFY_THRESHOLD - 1)
1411 treeifyBin(tab, hash);
1412 }
1413 ++modCount;
1414 ++size;
1415 afterNodeInsertion(true);
1416 return value;
1417 }
1418 }
1419
1420 @Override
1421 public void forEach(BiConsumer<? super K, ? super V> action) {
1422 Node<K,V>[] tab;
1423 if (action == null)
1424 throw new NullPointerException();
1425 if (size > 0 && (tab = table) != null) {
1426 int mc = modCount;
1427 for (Node<K,V> e : tab) {
1428 for (; e != null; e = e.next)
1429 action.accept(e.key, e.value);
1430 }
1431 if (modCount != mc)
1432 throw new ConcurrentModificationException();
1433 }
1434 }
1435
1436 @Override
1437 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1438 Node<K,V>[] tab;
1439 if (function == null)
1440 throw new NullPointerException();
1441 if (size > 0 && (tab = table) != null) {
1442 int mc = modCount;
1443 for (Node<K,V> e : tab) {
1444 for (; e != null; e = e.next) {
1445 e.value = function.apply(e.key, e.value);
1446 }
1447 }
1448 if (modCount != mc)
1449 throw new ConcurrentModificationException();
1450 }
1451 }
1452
1453 /* ------------------------------------------------------------ */
1454 // Cloning and serialization
1455
1456 /**
1457 * Returns a shallow copy of this {@code HashMap} instance: the keys and
1458 * values themselves are not cloned.
1459 *
1460 * @return a shallow copy of this map
1461 */
1462 @SuppressWarnings("unchecked")
1463 @Override
1464 public Object clone() {
1465 HashMap<K,V> result;
1466 try {
1467 result = (HashMap<K,V>)super.clone();
1468 } catch (CloneNotSupportedException e) {
1469 // this shouldn't happen, since we are Cloneable
1470 throw new InternalError(e);
1471 }
1472 result.reinitialize();
1473 result.putMapEntries(this, false);
1474 return result;
1475 }
1476
1477 // These methods are also used when serializing HashSets
1478 final float loadFactor() { return loadFactor; }
1479 final int capacity() {
1480 return (table != null) ? table.length :
1481 (threshold > 0) ? threshold :
1482 DEFAULT_INITIAL_CAPACITY;
1483 }
1484
1485 /**
1486 * Saves this map to a stream (that is, serializes it).
1487 *
1488 * @param s the stream
1489 * @throws IOException if an I/O error occurs
1490 * @serialData The <i>capacity</i> of the HashMap (the length of the
1491 * bucket array) is emitted (int), followed by the
1492 * <i>size</i> (an int, the number of key-value
1493 * mappings), followed by the key (Object) and value (Object)
1494 * for each key-value mapping. The key-value mappings are
1495 * emitted in no particular order.
1496 */
1497 @java.io.Serial
1498 private void writeObject(java.io.ObjectOutputStream s)
1499 throws IOException {
1500 int buckets = capacity();
1501 // Write out the threshold, loadfactor, and any hidden stuff
1502 s.defaultWriteObject();
1503 s.writeInt(buckets);
1504 s.writeInt(size);
1505 internalWriteEntries(s);
1506 }
1507
1508 /**
1509 * Reconstitutes this map from a stream (that is, deserializes it).
1510 * @param s the stream
1511 * @throws ClassNotFoundException if the class of a serialized object
1512 * could not be found
1513 * @throws IOException if an I/O error occurs
1514 */
1515 @java.io.Serial
1516 private void readObject(ObjectInputStream s)
1517 throws IOException, ClassNotFoundException {
1518
1519 ObjectInputStream.GetField fields = s.readFields();
1520
1521 // Read loadFactor (ignore threshold)
1522 float lf = fields.get("loadFactor", 0.75f);
1523 if (lf <= 0 || Float.isNaN(lf))
1524 throw new InvalidObjectException("Illegal load factor: " + lf);
1525
1526 lf = Math.clamp(lf, 0.25f, 4.0f);
1527 HashMap.UnsafeHolder.putLoadFactor(this, lf);
1528
1529 reinitialize();
1530
1531 s.readInt(); // Read and ignore number of buckets
1532 int mappings = s.readInt(); // Read number of mappings (size)
1533 if (mappings < 0) {
1534 throw new InvalidObjectException("Illegal mappings count: " + mappings);
1535 } else if (mappings == 0) {
1536 // use defaults
1537 } else if (mappings > 0) {
1538 double dc = Math.ceil(mappings / (double)lf);
1539 int cap = ((dc < DEFAULT_INITIAL_CAPACITY) ?
1540 DEFAULT_INITIAL_CAPACITY :
1541 (dc >= MAXIMUM_CAPACITY) ?
1542 MAXIMUM_CAPACITY :
1543 tableSizeFor((int)dc));
1544 float ft = (float)cap * lf;
1545 threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
1546 (int)ft : Integer.MAX_VALUE);
1547
1548 // Check Map.Entry[].class since it's the nearest public type to
1549 // what we're actually creating.
1550 SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Map.Entry[].class, cap);
1551 @SuppressWarnings({"rawtypes","unchecked"})
1552 Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
1553 table = tab;
1554
1555 // Read the keys and values, and put the mappings in the HashMap
1556 for (int i = 0; i < mappings; i++) {
1557 @SuppressWarnings("unchecked")
1558 K key = (K) s.readObject();
1559 @SuppressWarnings("unchecked")
1560 V value = (V) s.readObject();
1561 putVal(hash(key), key, value, false, false);
1562 }
1563 }
1564 }
1565
1566 // Support for resetting final field during deserializing
1567 private static final class UnsafeHolder {
1568 private UnsafeHolder() { throw new InternalError(); }
1569 private static final jdk.internal.misc.Unsafe unsafe
1570 = jdk.internal.misc.Unsafe.getUnsafe();
1571 private static final long LF_OFFSET
1572 = unsafe.objectFieldOffset(HashMap.class, "loadFactor");
1573 static void putLoadFactor(HashMap<?, ?> map, float lf) {
1574 unsafe.putFloat(map, LF_OFFSET, lf);
1575 }
1576 }
1577
1578 /* ------------------------------------------------------------ */
1579 // iterators
1580
1581 abstract class HashIterator {
1582 Node<K,V> next; // next entry to return
1583 Node<K,V> current; // current entry
1584 int expectedModCount; // for fast-fail
1585 int index; // current slot
1586
1587 HashIterator() {
1588 expectedModCount = modCount;
1589 Node<K,V>[] t = table;
1590 current = next = null;
1591 index = 0;
1592 if (t != null && size > 0) { // advance to first entry
1593 do {} while (index < t.length && (next = t[index++]) == null);
1594 }
1595 }
1596
1597 public final boolean hasNext() {
1598 return next != null;
1599 }
1600
1601 final Node<K,V> nextNode() {
1602 Node<K,V>[] t;
1603 Node<K,V> e = next;
1604 if (modCount != expectedModCount)
1605 throw new ConcurrentModificationException();
1606 if (e == null)
1607 throw new NoSuchElementException();
1608 if ((next = (current = e).next) == null && (t = table) != null) {
1609 do {} while (index < t.length && (next = t[index++]) == null);
1610 }
1611 return e;
1612 }
1613
1614 public final void remove() {
1615 Node<K,V> p = current;
1616 if (p == null)
1617 throw new IllegalStateException();
1618 if (modCount != expectedModCount)
1619 throw new ConcurrentModificationException();
1620 current = null;
1621 removeNode(p.hash, p.key, null, false, false);
1622 expectedModCount = modCount;
1623 }
1624 }
1625
1626 final class KeyIterator extends HashIterator
1627 implements Iterator<K> {
1628 public final K next() { return nextNode().key; }
1629 }
1630
1631 final class ValueIterator extends HashIterator
1632 implements Iterator<V> {
1633 public final V next() { return nextNode().value; }
1634 }
1635
1636 final class EntryIterator extends HashIterator
1637 implements Iterator<Map.Entry<K,V>> {
1638 public final Map.Entry<K,V> next() { return nextNode(); }
1639 }
1640
1641 /* ------------------------------------------------------------ */
1642 // spliterators
1643
1644 static class HashMapSpliterator<K,V> {
1645 final HashMap<K,V> map;
1646 Node<K,V> current; // current node
1647 int index; // current index, modified on advance/split
1648 int fence; // one past last index
1649 int est; // size estimate
1650 int expectedModCount; // for comodification checks
1651
1652 HashMapSpliterator(HashMap<K,V> m, int origin,
1653 int fence, int est,
1654 int expectedModCount) {
1655 this.map = m;
1656 this.index = origin;
1657 this.fence = fence;
1658 this.est = est;
1659 this.expectedModCount = expectedModCount;
1660 }
1661
1662 final int getFence() { // initialize fence and size on first use
1663 int hi;
1664 if ((hi = fence) < 0) {
1665 HashMap<K,V> m = map;
1666 est = m.size;
1667 expectedModCount = m.modCount;
1668 Node<K,V>[] tab = m.table;
1669 hi = fence = (tab == null) ? 0 : tab.length;
1670 }
1671 return hi;
1672 }
1673
1674 public final long estimateSize() {
1675 getFence(); // force init
1676 return (long) est;
1677 }
1678 }
1679
1680 static final class KeySpliterator<K,V>
1681 extends HashMapSpliterator<K,V>
1682 implements Spliterator<K> {
1683 KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
1684 int expectedModCount) {
1685 super(m, origin, fence, est, expectedModCount);
1686 }
1687
1688 public KeySpliterator<K,V> trySplit() {
1689 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1690 return (lo >= mid || current != null) ? null :
1691 new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
1692 expectedModCount);
1693 }
1694
1695 public void forEachRemaining(Consumer<? super K> action) {
1696 int i, hi, mc;
1697 if (action == null)
1698 throw new NullPointerException();
1699 HashMap<K,V> m = map;
1700 Node<K,V>[] tab = m.table;
1701 if ((hi = fence) < 0) {
1702 mc = expectedModCount = m.modCount;
1703 hi = fence = (tab == null) ? 0 : tab.length;
1704 }
1705 else
1706 mc = expectedModCount;
1707 if (tab != null && tab.length >= hi &&
1708 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1709 Node<K,V> p = current;
1710 current = null;
1711 do {
1712 if (p == null)
1713 p = tab[i++];
1714 else {
1715 action.accept(p.key);
1716 p = p.next;
1717 }
1718 } while (p != null || i < hi);
1719 if (m.modCount != mc)
1720 throw new ConcurrentModificationException();
1721 }
1722 }
1723
1724 public boolean tryAdvance(Consumer<? super K> action) {
1725 int hi;
1726 if (action == null)
1727 throw new NullPointerException();
1728 Node<K,V>[] tab = map.table;
1729 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1730 while (current != null || index < hi) {
1731 if (current == null)
1732 current = tab[index++];
1733 else {
1734 K k = current.key;
1735 current = current.next;
1736 action.accept(k);
1737 if (map.modCount != expectedModCount)
1738 throw new ConcurrentModificationException();
1739 return true;
1740 }
1741 }
1742 }
1743 return false;
1744 }
1745
1746 public int characteristics() {
1747 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
1748 Spliterator.DISTINCT;
1749 }
1750 }
1751
1752 static final class ValueSpliterator<K,V>
1753 extends HashMapSpliterator<K,V>
1754 implements Spliterator<V> {
1755 ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
1756 int expectedModCount) {
1757 super(m, origin, fence, est, expectedModCount);
1758 }
1759
1760 public ValueSpliterator<K,V> trySplit() {
1761 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1762 return (lo >= mid || current != null) ? null :
1763 new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
1764 expectedModCount);
1765 }
1766
1767 public void forEachRemaining(Consumer<? super V> action) {
1768 int i, hi, mc;
1769 if (action == null)
1770 throw new NullPointerException();
1771 HashMap<K,V> m = map;
1772 Node<K,V>[] tab = m.table;
1773 if ((hi = fence) < 0) {
1774 mc = expectedModCount = m.modCount;
1775 hi = fence = (tab == null) ? 0 : tab.length;
1776 }
1777 else
1778 mc = expectedModCount;
1779 if (tab != null && tab.length >= hi &&
1780 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1781 Node<K,V> p = current;
1782 current = null;
1783 do {
1784 if (p == null)
1785 p = tab[i++];
1786 else {
1787 action.accept(p.value);
1788 p = p.next;
1789 }
1790 } while (p != null || i < hi);
1791 if (m.modCount != mc)
1792 throw new ConcurrentModificationException();
1793 }
1794 }
1795
1796 public boolean tryAdvance(Consumer<? super V> action) {
1797 int hi;
1798 if (action == null)
1799 throw new NullPointerException();
1800 Node<K,V>[] tab = map.table;
1801 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1802 while (current != null || index < hi) {
1803 if (current == null)
1804 current = tab[index++];
1805 else {
1806 V v = current.value;
1807 current = current.next;
1808 action.accept(v);
1809 if (map.modCount != expectedModCount)
1810 throw new ConcurrentModificationException();
1811 return true;
1812 }
1813 }
1814 }
1815 return false;
1816 }
1817
1818 public int characteristics() {
1819 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
1820 }
1821 }
1822
1823 static final class EntrySpliterator<K,V>
1824 extends HashMapSpliterator<K,V>
1825 implements Spliterator<Map.Entry<K,V>> {
1826 EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
1827 int expectedModCount) {
1828 super(m, origin, fence, est, expectedModCount);
1829 }
1830
1831 public EntrySpliterator<K,V> trySplit() {
1832 int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1833 return (lo >= mid || current != null) ? null :
1834 new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
1835 expectedModCount);
1836 }
1837
1838 public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
1839 int i, hi, mc;
1840 if (action == null)
1841 throw new NullPointerException();
1842 HashMap<K,V> m = map;
1843 Node<K,V>[] tab = m.table;
1844 if ((hi = fence) < 0) {
1845 mc = expectedModCount = m.modCount;
1846 hi = fence = (tab == null) ? 0 : tab.length;
1847 }
1848 else
1849 mc = expectedModCount;
1850 if (tab != null && tab.length >= hi &&
1851 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1852 Node<K,V> p = current;
1853 current = null;
1854 do {
1855 if (p == null)
1856 p = tab[i++];
1857 else {
1858 action.accept(p);
1859 p = p.next;
1860 }
1861 } while (p != null || i < hi);
1862 if (m.modCount != mc)
1863 throw new ConcurrentModificationException();
1864 }
1865 }
1866
1867 public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
1868 int hi;
1869 if (action == null)
1870 throw new NullPointerException();
1871 Node<K,V>[] tab = map.table;
1872 if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1873 while (current != null || index < hi) {
1874 if (current == null)
1875 current = tab[index++];
1876 else {
1877 Node<K,V> e = current;
1878 current = current.next;
1879 action.accept(e);
1880 if (map.modCount != expectedModCount)
1881 throw new ConcurrentModificationException();
1882 return true;
1883 }
1884 }
1885 }
1886 return false;
1887 }
1888
1889 public int characteristics() {
1890 return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
1891 Spliterator.DISTINCT;
1892 }
1893 }
1894
1895 /* ------------------------------------------------------------ */
1896 // LinkedHashMap support
1897
1898
1899 /*
1900 * The following package-protected methods are designed to be
1901 * overridden by LinkedHashMap, but not by any other subclass.
1902 * Nearly all other internal methods are also package-protected
1903 * but are declared final, so can be used by LinkedHashMap, view
1904 * classes, and HashSet.
1905 */
1906
1907 // Create a regular (non-tree) node
1908 Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
1909 return new Node<>(hash, key, value, next);
1910 }
1911
1912 // For conversion from TreeNodes to plain nodes
1913 Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
1914 return new Node<>(p.hash, p.key, p.value, next);
1915 }
1916
1917 // Create a tree bin node
1918 TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
1919 return new TreeNode<>(hash, key, value, next);
1920 }
1921
1922 // For treeifyBin
1923 TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
1924 return new TreeNode<>(p.hash, p.key, p.value, next);
1925 }
1926
1927 /**
1928 * Reset to initial default state. Called by clone and readObject.
1929 */
1930 void reinitialize() {
1931 table = null;
1932 entrySet = null;
1933 keySet = null;
1934 values = null;
1935 modCount = 0;
1936 threshold = 0;
1937 size = 0;
1938 }
1939
1940 // Callbacks to allow LinkedHashMap post-actions
1941 void afterNodeAccess(Node<K,V> p) { }
1942 void afterNodeInsertion(boolean evict) { }
1943 void afterNodeRemoval(Node<K,V> p) { }
1944
1945 // Called only from writeObject, to ensure compatible ordering.
1946 void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
1947 Node<K,V>[] tab;
1948 if (size > 0 && (tab = table) != null) {
1949 for (Node<K,V> e : tab) {
1950 for (; e != null; e = e.next) {
1951 s.writeObject(e.key);
1952 s.writeObject(e.value);
1953 }
1954 }
1955 }
1956 }
1957
1958 /* ------------------------------------------------------------ */
1959 // Tree bins
1960
1961 /**
1962 * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
1963 * extends Node) so can be used as extension of either regular or
1964 * linked node.
1965 */
1966 static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
1967 TreeNode<K,V> parent; // red-black tree links
1968 TreeNode<K,V> left;
1969 TreeNode<K,V> right;
1970 TreeNode<K,V> prev; // needed to unlink next upon deletion
1971 boolean red;
1972 TreeNode(int hash, K key, V val, Node<K,V> next) {
1973 super(hash, key, val, next);
1974 }
1975
1976 /**
1977 * Returns root of tree containing this node.
1978 */
1979 final TreeNode<K,V> root() {
1980 for (TreeNode<K,V> r = this, p;;) {
1981 if ((p = r.parent) == null)
1982 return r;
1983 r = p;
1984 }
1985 }
1986
1987 /**
1988 * Ensures that the given root is the first node of its bin.
1989 */
1990 static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
1991 int n;
1992 if (root != null && tab != null && (n = tab.length) > 0) {
1993 int index = (n - 1) & root.hash;
1994 TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
1995 if (root != first) {
1996 Node<K,V> rn;
1997 tab[index] = root;
1998 TreeNode<K,V> rp = root.prev;
1999 if ((rn = root.next) != null)
2000 ((TreeNode<K,V>)rn).prev = rp;
2001 if (rp != null)
2002 rp.next = rn;
2003 if (first != null)
2004 first.prev = root;
2005 root.next = first;
2006 root.prev = null;
2007 }
2008 assert checkInvariants(root);
2009 }
2010 }
2011
2012 /**
2013 * Finds the node starting at root p with the given hash and key.
2014 * The kc argument caches comparableClassFor(key) upon first use
2015 * comparing keys.
2016 */
2017 final TreeNode<K,V> find(int h, Object k, Class<?> kc) {
2018 TreeNode<K,V> p = this;
2019 do {
2020 int ph, dir; K pk;
2021 TreeNode<K,V> pl = p.left, pr = p.right, q;
2022 if ((ph = p.hash) > h)
2023 p = pl;
2024 else if (ph < h)
2025 p = pr;
2026 else if (Objects.equals(k, (pk = p.key)))
2027 return p;
2028 else if (pl == null)
2029 p = pr;
2030 else if (pr == null)
2031 p = pl;
2032 else if ((kc != null ||
2033 (kc = comparableClassFor(k)) != null) &&
2034 (dir = compareComparables(kc, k, pk)) != 0)
2035 p = (dir < 0) ? pl : pr;
2036 else if ((q = pr.find(h, k, kc)) != null)
2037 return q;
2038 else
2039 p = pl;
2040 } while (p != null);
2041 return null;
2042 }
2043
2044 /**
2045 * Calls find for root node.
2046 */
2047 final TreeNode<K,V> getTreeNode(int h, Object k) {
2048 return ((parent != null) ? root() : this).find(h, k, null);
2049 }
2050
2051 /**
2052 * Tie-breaking utility for ordering insertions when equal
2053 * hashCodes and non-comparable. We don't require a total
2054 * order, just a consistent insertion rule to maintain
2055 * equivalence across rebalancings. Tie-breaking further than
2056 * necessary simplifies testing a bit.
2057 */
2058 static int tieBreakOrder(Object a, Object b) {
2059 int d;
2060 if (a == null || b == null ||
2061 (d = a.getClass().getName().
2062 compareTo(b.getClass().getName())) == 0)
2063 d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
2064 -1 : 1);
2065 return d;
2066 }
2067
2068 /**
2069 * Forms tree of the nodes linked from this node.
2070 */
2071 final void treeify(Node<K,V>[] tab) {
2072 TreeNode<K,V> root = null;
2073 for (TreeNode<K,V> x = this, next; x != null; x = next) {
2074 next = (TreeNode<K,V>)x.next;
2075 x.left = x.right = null;
2076 if (root == null) {
2077 x.parent = null;
2078 x.red = false;
2079 root = x;
2080 }
2081 else {
2082 K k = x.key;
2083 int h = x.hash;
2084 Class<?> kc = null;
2085 for (TreeNode<K,V> p = root;;) {
2086 int dir, ph;
2087 K pk = p.key;
2088 if ((ph = p.hash) > h)
2089 dir = -1;
2090 else if (ph < h)
2091 dir = 1;
2092 else if ((kc == null &&
2093 (kc = comparableClassFor(k)) == null) ||
2094 (dir = compareComparables(kc, k, pk)) == 0)
2095 dir = tieBreakOrder(k, pk);
2096
2097 TreeNode<K,V> xp = p;
2098 if ((p = (dir <= 0) ? p.left : p.right) == null) {
2099 x.parent = xp;
2100 if (dir <= 0)
2101 xp.left = x;
2102 else
2103 xp.right = x;
2104 root = balanceInsertion(root, x);
2105 break;
2106 }
2107 }
2108 }
2109 }
2110 moveRootToFront(tab, root);
2111 }
2112
2113 /**
2114 * Returns a list of non-TreeNodes replacing those linked from
2115 * this node.
2116 */
2117 final Node<K,V> untreeify(HashMap<K,V> map) {
2118 Node<K,V> hd = null, tl = null;
2119 for (Node<K,V> q = this; q != null; q = q.next) {
2120 Node<K,V> p = map.replacementNode(q, null);
2121 if (tl == null)
2122 hd = p;
2123 else
2124 tl.next = p;
2125 tl = p;
2126 }
2127 return hd;
2128 }
2129
2130 /**
2131 * Tree version of putVal.
2132 */
2133 final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
2134 int h, K k, V v) {
2135 Class<?> kc = null;
2136 boolean searched = false;
2137 TreeNode<K,V> root = (parent != null) ? root() : this;
2138 for (TreeNode<K,V> p = root;;) {
2139 int dir, ph; K pk;
2140 if ((ph = p.hash) > h)
2141 dir = -1;
2142 else if (ph < h)
2143 dir = 1;
2144 else if (Objects.equals(k, (pk = p.key)))
2145 return p;
2146 else if ((kc == null &&
2147 (kc = comparableClassFor(k)) == null) ||
2148 (dir = compareComparables(kc, k, pk)) == 0) {
2149 if (!searched) {
2150 TreeNode<K,V> q, ch;
2151 searched = true;
2152 if (((ch = p.left) != null &&
2153 (q = ch.find(h, k, kc)) != null) ||
2154 ((ch = p.right) != null &&
2155 (q = ch.find(h, k, kc)) != null))
2156 return q;
2157 }
2158 dir = tieBreakOrder(k, pk);
2159 }
2160
2161 TreeNode<K,V> xp = p;
2162 if ((p = (dir <= 0) ? p.left : p.right) == null) {
2163 Node<K,V> xpn = xp.next;
2164 TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
2165 if (dir <= 0)
2166 xp.left = x;
2167 else
2168 xp.right = x;
2169 xp.next = x;
2170 x.parent = x.prev = xp;
2171 if (xpn != null)
2172 ((TreeNode<K,V>)xpn).prev = x;
2173 moveRootToFront(tab, balanceInsertion(root, x));
2174 return null;
2175 }
2176 }
2177 }
2178
2179 /**
2180 * Removes the given node, that must be present before this call.
2181 * This is messier than typical red-black deletion code because we
2182 * cannot swap the contents of an interior node with a leaf
2183 * successor that is pinned by "next" pointers that are accessible
2184 * independently during traversal. So instead we swap the tree
2185 * linkages. If the current tree appears to have too few nodes,
2186 * the bin is converted back to a plain bin. (The test triggers
2187 * somewhere between 2 and 6 nodes, depending on tree structure).
2188 */
2189 final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
2190 boolean movable) {
2191 int n;
2192 if (tab == null || (n = tab.length) == 0)
2193 return;
2194 int index = (n - 1) & hash;
2195 TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
2196 TreeNode<K,V> succ = (TreeNode<K,V>)next, pred = prev;
2197 if (pred == null)
2198 tab[index] = first = succ;
2199 else
2200 pred.next = succ;
2201 if (succ != null)
2202 succ.prev = pred;
2203 if (first == null)
2204 return;
2205 if (root.parent != null)
2206 root = root.root();
2207 if (root == null
2208 || (movable
2209 && (root.right == null
2210 || (rl = root.left) == null
2211 || rl.left == null))) {
2212 tab[index] = first.untreeify(map); // too small
2213 return;
2214 }
2215 TreeNode<K,V> p = this, pl = left, pr = right, replacement;
2216 if (pl != null && pr != null) {
2217 TreeNode<K,V> s = pr, sl;
2218 while ((sl = s.left) != null) // find successor
2219 s = sl;
2220 boolean c = s.red; s.red = p.red; p.red = c; // swap colors
2221 TreeNode<K,V> sr = s.right;
2222 TreeNode<K,V> pp = p.parent;
2223 if (s == pr) { // p was s's direct parent
2224 p.parent = s;
2225 s.right = p;
2226 }
2227 else {
2228 TreeNode<K,V> sp = s.parent;
2229 if ((p.parent = sp) != null) {
2230 if (s == sp.left)
2231 sp.left = p;
2232 else
2233 sp.right = p;
2234 }
2235 if ((s.right = pr) != null)
2236 pr.parent = s;
2237 }
2238 p.left = null;
2239 if ((p.right = sr) != null)
2240 sr.parent = p;
2241 if ((s.left = pl) != null)
2242 pl.parent = s;
2243 if ((s.parent = pp) == null)
2244 root = s;
2245 else if (p == pp.left)
2246 pp.left = s;
2247 else
2248 pp.right = s;
2249 if (sr != null)
2250 replacement = sr;
2251 else
2252 replacement = p;
2253 }
2254 else if (pl != null)
2255 replacement = pl;
2256 else if (pr != null)
2257 replacement = pr;
2258 else
2259 replacement = p;
2260 if (replacement != p) {
2261 TreeNode<K,V> pp = replacement.parent = p.parent;
2262 if (pp == null)
2263 (root = replacement).red = false;
2264 else if (p == pp.left)
2265 pp.left = replacement;
2266 else
2267 pp.right = replacement;
2268 p.left = p.right = p.parent = null;
2269 }
2270
2271 TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);
2272
2273 if (replacement == p) { // detach
2274 TreeNode<K,V> pp = p.parent;
2275 p.parent = null;
2276 if (pp != null) {
2277 if (p == pp.left)
2278 pp.left = null;
2279 else if (p == pp.right)
2280 pp.right = null;
2281 }
2282 }
2283 if (movable)
2284 moveRootToFront(tab, r);
2285 }
2286
2287 /**
2288 * Splits nodes in a tree bin into lower and upper tree bins,
2289 * or untreeifies if now too small. Called only from resize;
2290 * see above discussion about split bits and indices.
2291 *
2292 * @param map the map
2293 * @param tab the table for recording bin heads
2294 * @param index the index of the table being split
2295 * @param bit the bit of hash to split on
2296 */
2297 final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
2298 TreeNode<K,V> b = this;
2299 // Relink into lo and hi lists, preserving order
2300 TreeNode<K,V> loHead = null, loTail = null;
2301 TreeNode<K,V> hiHead = null, hiTail = null;
2302 int lc = 0, hc = 0;
2303 for (TreeNode<K,V> e = b, next; e != null; e = next) {
2304 next = (TreeNode<K,V>)e.next;
2305 e.next = null;
2306 if ((e.hash & bit) == 0) {
2307 if ((e.prev = loTail) == null)
2308 loHead = e;
2309 else
2310 loTail.next = e;
2311 loTail = e;
2312 ++lc;
2313 }
2314 else {
2315 if ((e.prev = hiTail) == null)
2316 hiHead = e;
2317 else
2318 hiTail.next = e;
2319 hiTail = e;
2320 ++hc;
2321 }
2322 }
2323
2324 if (loHead != null) {
2325 if (lc <= UNTREEIFY_THRESHOLD)
2326 tab[index] = loHead.untreeify(map);
2327 else {
2328 tab[index] = loHead;
2329 if (hiHead != null) // (else is already treeified)
2330 loHead.treeify(tab);
2331 }
2332 }
2333 if (hiHead != null) {
2334 if (hc <= UNTREEIFY_THRESHOLD)
2335 tab[index + bit] = hiHead.untreeify(map);
2336 else {
2337 tab[index + bit] = hiHead;
2338 if (loHead != null)
2339 hiHead.treeify(tab);
2340 }
2341 }
2342 }
2343
2344 /* ------------------------------------------------------------ */
2345 // Red-black tree methods, all adapted from CLR
2346
2347 static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
2348 TreeNode<K,V> p) {
2349 TreeNode<K,V> r, pp, rl;
2350 if (p != null && (r = p.right) != null) {
2351 if ((rl = p.right = r.left) != null)
2352 rl.parent = p;
2353 if ((pp = r.parent = p.parent) == null)
2354 (root = r).red = false;
2355 else if (pp.left == p)
2356 pp.left = r;
2357 else
2358 pp.right = r;
2359 r.left = p;
2360 p.parent = r;
2361 }
2362 return root;
2363 }
2364
2365 static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
2366 TreeNode<K,V> p) {
2367 TreeNode<K,V> l, pp, lr;
2368 if (p != null && (l = p.left) != null) {
2369 if ((lr = p.left = l.right) != null)
2370 lr.parent = p;
2371 if ((pp = l.parent = p.parent) == null)
2372 (root = l).red = false;
2373 else if (pp.right == p)
2374 pp.right = l;
2375 else
2376 pp.left = l;
2377 l.right = p;
2378 p.parent = l;
2379 }
2380 return root;
2381 }
2382
2383 static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
2384 TreeNode<K,V> x) {
2385 x.red = true;
2386 for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {
2387 if ((xp = x.parent) == null) {
2388 x.red = false;
2389 return x;
2390 }
2391 else if (!xp.red || (xpp = xp.parent) == null)
2392 return root;
2393 if (xp == (xppl = xpp.left)) {
2394 if ((xppr = xpp.right) != null && xppr.red) {
2395 xppr.red = false;
2396 xp.red = false;
2397 xpp.red = true;
2398 x = xpp;
2399 }
2400 else {
2401 if (x == xp.right) {
2402 root = rotateLeft(root, x = xp);
2403 xpp = (xp = x.parent) == null ? null : xp.parent;
2404 }
2405 if (xp != null) {
2406 xp.red = false;
2407 if (xpp != null) {
2408 xpp.red = true;
2409 root = rotateRight(root, xpp);
2410 }
2411 }
2412 }
2413 }
2414 else {
2415 if (xppl != null && xppl.red) {
2416 xppl.red = false;
2417 xp.red = false;
2418 xpp.red = true;
2419 x = xpp;
2420 }
2421 else {
2422 if (x == xp.left) {
2423 root = rotateRight(root, x = xp);
2424 xpp = (xp = x.parent) == null ? null : xp.parent;
2425 }
2426 if (xp != null) {
2427 xp.red = false;
2428 if (xpp != null) {
2429 xpp.red = true;
2430 root = rotateLeft(root, xpp);
2431 }
2432 }
2433 }
2434 }
2435 }
2436 }
2437
2438 static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
2439 TreeNode<K,V> x) {
2440 for (TreeNode<K,V> xp, xpl, xpr;;) {
2441 if (x == null || x == root)
2442 return root;
2443 else if ((xp = x.parent) == null) {
2444 x.red = false;
2445 return x;
2446 }
2447 else if (x.red) {
2448 x.red = false;
2449 return root;
2450 }
2451 else if ((xpl = xp.left) == x) {
2452 if ((xpr = xp.right) != null && xpr.red) {
2453 xpr.red = false;
2454 xp.red = true;
2455 root = rotateLeft(root, xp);
2456 xpr = (xp = x.parent) == null ? null : xp.right;
2457 }
2458 if (xpr == null)
2459 x = xp;
2460 else {
2461 TreeNode<K,V> sl = xpr.left, sr = xpr.right;
2462 if ((sr == null || !sr.red) &&
2463 (sl == null || !sl.red)) {
2464 xpr.red = true;
2465 x = xp;
2466 }
2467 else {
2468 if (sr == null || !sr.red) {
2469 if (sl != null)
2470 sl.red = false;
2471 xpr.red = true;
2472 root = rotateRight(root, xpr);
2473 xpr = (xp = x.parent) == null ?
2474 null : xp.right;
2475 }
2476 if (xpr != null) {
2477 xpr.red = (xp == null) ? false : xp.red;
2478 if ((sr = xpr.right) != null)
2479 sr.red = false;
2480 }
2481 if (xp != null) {
2482 xp.red = false;
2483 root = rotateLeft(root, xp);
2484 }
2485 x = root;
2486 }
2487 }
2488 }
2489 else { // symmetric
2490 if (xpl != null && xpl.red) {
2491 xpl.red = false;
2492 xp.red = true;
2493 root = rotateRight(root, xp);
2494 xpl = (xp = x.parent) == null ? null : xp.left;
2495 }
2496 if (xpl == null)
2497 x = xp;
2498 else {
2499 TreeNode<K,V> sl = xpl.left, sr = xpl.right;
2500 if ((sl == null || !sl.red) &&
2501 (sr == null || !sr.red)) {
2502 xpl.red = true;
2503 x = xp;
2504 }
2505 else {
2506 if (sl == null || !sl.red) {
2507 if (sr != null)
2508 sr.red = false;
2509 xpl.red = true;
2510 root = rotateLeft(root, xpl);
2511 xpl = (xp = x.parent) == null ?
2512 null : xp.left;
2513 }
2514 if (xpl != null) {
2515 xpl.red = (xp == null) ? false : xp.red;
2516 if ((sl = xpl.left) != null)
2517 sl.red = false;
2518 }
2519 if (xp != null) {
2520 xp.red = false;
2521 root = rotateRight(root, xp);
2522 }
2523 x = root;
2524 }
2525 }
2526 }
2527 }
2528 }
2529
2530 /**
2531 * Recursive invariant check
2532 */
2533 static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
2534 TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
2535 tb = t.prev, tn = (TreeNode<K,V>)t.next;
2536 if (tb != null && tb.next != t)
2537 return false;
2538 if (tn != null && tn.prev != t)
2539 return false;
2540 if (tp != null && t != tp.left && t != tp.right)
2541 return false;
2542 if (tl != null && (tl.parent != t || tl.hash > t.hash))
2543 return false;
2544 if (tr != null && (tr.parent != t || tr.hash < t.hash))
2545 return false;
2546 if (t.red && tl != null && tl.red && tr != null && tr.red)
2547 return false;
2548 if (tl != null && !checkInvariants(tl))
2549 return false;
2550 if (tr != null && !checkInvariants(tr))
2551 return false;
2552 return true;
2553 }
2554 }
2555
2556 /**
2557 * Calculate initial capacity for HashMap based classes, from expected size and default load factor (0.75).
2558 *
2559 * @param numMappings the expected number of mappings
2560 * @return initial capacity for HashMap based classes.
2561 * @since 19
2562 */
2563 static int calculateHashMapCapacity(int numMappings) {
2564 return (int) Math.ceil(numMappings / (double) DEFAULT_LOAD_FACTOR);
2565 }
2566
2567 /**
2568 * Creates a new, empty HashMap suitable for the expected number of mappings.
2569 * The returned map uses the default load factor of 0.75, and its initial capacity is
2570 * generally large enough so that the expected number of mappings can be added
2571 * without resizing the map.
2572 *
2573 * @param numMappings the expected number of mappings
2574 * @param <K> the type of keys maintained by the new map
2575 * @param <V> the type of mapped values
2576 * @return the newly created map
2577 * @throws IllegalArgumentException if numMappings is negative
2578 * @since 19
2579 */
2580 public static <K, V> HashMap<K, V> newHashMap(int numMappings) {
2581 if (numMappings < 0) {
2582 throw new IllegalArgumentException("Negative number of mappings: " + numMappings);
2583 }
2584 return new HashMap<>(calculateHashMapCapacity(numMappings));
2585 }
2586
2587 }