imported patch loadFactor-isNaN

   1 /*
   2  * Copyright (c) 1997, 2018, 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.reflect.ParameterizedType;
  32 import java.lang.reflect.Type;
  33 import java.util.function.BiConsumer;
  34 import java.util.function.BiFunction;
  35 import java.util.function.Consumer;
  36 import java.util.function.Function;
  37 import jdk.internal.access.SharedSecrets;
  38 
  39 /**
  40  * Hash table based implementation of the {@code Map} interface.  This
  41  * implementation provides all of the optional map operations, and permits
  42  * {@code null} values and the {@code null} key.  (The {@code HashMap}
  43  * class is roughly equivalent to {@code Hashtable}, 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 ({@code get} and {@code put}), 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  * {@code HashMap} 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 {@code HashMap} 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 {@code HashMap} class, including
  72  * {@code get} and {@code put}).  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 {@code HashMap}
  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  * {@code remove} 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 {@code ConcurrentModificationException} 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}/java.base/java/util/package-summary.html#CollectionsFramework">
 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     /**
 343      * Returns x's Class if it is of the form "class C implements
 344      * Comparable<C>", else null.
 345      */
 346     static Class<?> comparableClassFor(Object x) {
 347         if (x instanceof Comparable) {
 348             Class<?> c; Type[] ts, as; ParameterizedType p;
 349             if ((c = x.getClass()) == String.class) // bypass checks
 350                 return c;
 351             if ((ts = c.getGenericInterfaces()) != null) {
 352                 for (Type t : ts) {
 353                     if ((t instanceof ParameterizedType) &&
 354                         ((p = (ParameterizedType) t).getRawType() ==
 355                          Comparable.class) &&
 356                         (as = p.getActualTypeArguments()) != null &&
 357                         as.length == 1 && as[0] == c) // type arg is c
 358                         return c;
 359                 }
 360             }
 361         }
 362         return null;
 363     }
 364 
 365     /**
 366      * Returns k.compareTo(x) if x matches kc (k's screened comparable
 367      * class), else 0.
 368      */
 369     @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable
 370     static int compareComparables(Class<?> kc, Object k, Object x) {
 371         return (x == null || x.getClass() != kc ? 0 :
 372                 ((Comparable)k).compareTo(x));
 373     }
 374 
 375     /**
 376      * Returns a power of two size for the given target capacity.
 377      */
 378     static final int tableSizeFor(int cap) {
 379         int n = -1 >>> Integer.numberOfLeadingZeros(cap - 1);
 380         return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
 381     }
 382 
 383     /* ---------------- Fields -------------- */
 384 
 385     /**
 386      * The table, initialized on first use, and resized as
 387      * necessary. When allocated, length is always a power of two.
 388      * (We also tolerate length zero in some operations to allow
 389      * bootstrapping mechanics that are currently not needed.)
 390      */
 391     transient Node<K,V>[] table;
 392 
 393     /**
 394      * Holds cached entrySet(). Note that AbstractMap fields are used
 395      * for keySet() and values().
 396      */
 397     transient Set<Map.Entry<K,V>> entrySet;
 398 
 399     /**
 400      * The number of key-value mappings contained in this map.
 401      */
 402     transient int size;
 403 
 404     /**
 405      * The number of times this HashMap has been structurally modified
 406      * Structural modifications are those that change the number of mappings in
 407      * the HashMap or otherwise modify its internal structure (e.g.,
 408      * rehash).  This field is used to make iterators on Collection-views of
 409      * the HashMap fail-fast.  (See ConcurrentModificationException).
 410      */
 411     transient int modCount;
 412 
 413     /**
 414      * The next size value at which to resize (capacity * load factor).
 415      *
 416      * @serial
 417      */
 418     // (The javadoc description is true upon serialization.
 419     // Additionally, if the table array has not been allocated, this
 420     // field holds the initial array capacity, or zero signifying
 421     // DEFAULT_INITIAL_CAPACITY.)
 422     int threshold;
 423 
 424     /**
 425      * The load factor for the hash table.
 426      *
 427      * @serial
 428      */
 429     final float loadFactor;
 430 
 431     /* ---------------- Public operations -------------- */
 432 
 433     /**
 434      * Constructs an empty {@code HashMap} with the specified initial
 435      * capacity and load factor.
 436      *
 437      * @param  initialCapacity the initial capacity
 438      * @param  loadFactor      the load factor
 439      * @throws IllegalArgumentException if the initial capacity is negative
 440      *         or the load factor is nonpositive
 441      */
 442     public HashMap(int initialCapacity, float loadFactor) {
 443         if (initialCapacity < 0)
 444             throw new IllegalArgumentException("Illegal initial capacity: " +
 445                                                initialCapacity);
 446         if (initialCapacity > MAXIMUM_CAPACITY)
 447             initialCapacity = MAXIMUM_CAPACITY;
 448         if (!(loadFactor > 0))          // also checks for NaNs
 449             throw new IllegalArgumentException("Illegal load factor: " +
 450                                                loadFactor);
 451         this.loadFactor = loadFactor;
 452         this.threshold = tableSizeFor(initialCapacity);
 453     }
 454 
 455     /**
 456      * Constructs an empty {@code HashMap} with the specified initial
 457      * capacity and the default load factor (0.75).
 458      *
 459      * @param  initialCapacity the initial capacity.
 460      * @throws IllegalArgumentException if the initial capacity is negative.
 461      */
 462     public HashMap(int initialCapacity) {
 463         this(initialCapacity, DEFAULT_LOAD_FACTOR);
 464     }
 465 
 466     /**
 467      * Constructs an empty {@code HashMap} with the default initial capacity
 468      * (16) and the default load factor (0.75).
 469      */
 470     public HashMap() {
 471         this.loadFactor = DEFAULT_LOAD_FACTOR; // all other fields defaulted
 472     }
 473 
 474     /**
 475      * Constructs a new {@code HashMap} with the same mappings as the
 476      * specified {@code Map}.  The {@code HashMap} is created with
 477      * default load factor (0.75) and an initial capacity sufficient to
 478      * hold the mappings in the specified {@code Map}.
 479      *
 480      * @param   m the map whose mappings are to be placed in this map
 481      * @throws  NullPointerException if the specified map is null
 482      */
 483     public HashMap(Map<? extends K, ? extends V> m) {
 484         this.loadFactor = DEFAULT_LOAD_FACTOR;
 485         putMapEntries(m, false);
 486     }
 487 
 488     /**
 489      * Implements Map.putAll and Map constructor.
 490      *
 491      * @param m the map
 492      * @param evict false when initially constructing this map, else
 493      * true (relayed to method afterNodeInsertion).
 494      */
 495     final void putMapEntries(Map<? extends K, ? extends V> m, boolean evict) {
 496         int s = m.size();
 497         if (s > 0) {
 498             if (table == null) { // pre-size
 499                 float ft = ((float)s / loadFactor) + 1.0F;
 500                 int t = ((ft < (float)MAXIMUM_CAPACITY) ?
 501                          (int)ft : MAXIMUM_CAPACITY);
 502                 if (t > threshold)
 503                     threshold = tableSizeFor(t);
 504             }
 505             else if (s > threshold)
 506                 resize();
 507             for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
 508                 K key = e.getKey();
 509                 V value = e.getValue();
 510                 putVal(hash(key), key, value, false, evict);
 511             }
 512         }
 513     }
 514 
 515     /**
 516      * Returns the number of key-value mappings in this map.
 517      *
 518      * @return the number of key-value mappings in this map
 519      */
 520     public int size() {
 521         return size;
 522     }
 523 
 524     /**
 525      * Returns {@code true} if this map contains no key-value mappings.
 526      *
 527      * @return {@code true} if this map contains no key-value mappings
 528      */
 529     public boolean isEmpty() {
 530         return size == 0;
 531     }
 532 
 533     /**
 534      * Returns the value to which the specified key is mapped,
 535      * or {@code null} if this map contains no mapping for the key.
 536      *
 537      * <p>More formally, if this map contains a mapping from a key
 538      * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
 539      * key.equals(k))}, then this method returns {@code v}; otherwise
 540      * it returns {@code null}.  (There can be at most one such mapping.)
 541      *
 542      * <p>A return value of {@code null} does not <i>necessarily</i>
 543      * indicate that the map contains no mapping for the key; it's also
 544      * possible that the map explicitly maps the key to {@code null}.
 545      * The {@link #containsKey containsKey} operation may be used to
 546      * distinguish these two cases.
 547      *
 548      * @see #put(Object, Object)
 549      */
 550     public V get(Object key) {
 551         Node<K,V> e;
 552         return (e = getNode(hash(key), key)) == null ? null : e.value;
 553     }
 554 
 555     /**
 556      * Implements Map.get and related methods.
 557      *
 558      * @param hash hash for key
 559      * @param key the key
 560      * @return the node, or null if none
 561      */
 562     final Node<K,V> getNode(int hash, Object key) {
 563         Node<K,V>[] tab; Node<K,V> first, e; int n; K k;
 564         if ((tab = table) != null && (n = tab.length) > 0 &&
 565             (first = tab[(n - 1) & hash]) != null) {
 566             if (first.hash == hash && // always check first node
 567                 ((k = first.key) == key || (key != null && key.equals(k))))
 568                 return first;
 569             if ((e = first.next) != null) {
 570                 if (first instanceof TreeNode)
 571                     return ((TreeNode<K,V>)first).getTreeNode(hash, key);
 572                 do {
 573                     if (e.hash == hash &&
 574                         ((k = e.key) == key || (key != null && key.equals(k))))
 575                         return e;
 576                 } while ((e = e.next) != null);
 577             }
 578         }
 579         return null;
 580     }
 581 
 582     /**
 583      * Returns {@code true} if this map contains a mapping for the
 584      * specified key.
 585      *
 586      * @param   key   The key whose presence in this map is to be tested
 587      * @return {@code true} if this map contains a mapping for the specified
 588      * key.
 589      */
 590     public boolean containsKey(Object key) {
 591         return getNode(hash(key), key) != null;
 592     }
 593 
 594     /**
 595      * Associates the specified value with the specified key in this map.
 596      * If the map previously contained a mapping for the key, the old
 597      * value is replaced.
 598      *
 599      * @param key key with which the specified value is to be associated
 600      * @param value value to be associated with the specified key
 601      * @return the previous value associated with {@code key}, or
 602      *         {@code null} if there was no mapping for {@code key}.
 603      *         (A {@code null} return can also indicate that the map
 604      *         previously associated {@code null} with {@code key}.)
 605      */
 606     public V put(K key, V value) {
 607         return putVal(hash(key), key, value, false, true);
 608     }
 609 
 610     /**
 611      * Implements Map.put and related methods.
 612      *
 613      * @param hash hash for key
 614      * @param key the key
 615      * @param value the value to put
 616      * @param onlyIfAbsent if true, don't change existing value
 617      * @param evict if false, the table is in creation mode.
 618      * @return previous value, or null if none
 619      */
 620     final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
 621                    boolean evict) {
 622         Node<K,V>[] tab; Node<K,V> p; int n, i;
 623         if ((tab = table) == null || (n = tab.length) == 0)
 624             n = (tab = resize()).length;
 625         if ((p = tab[i = (n - 1) & hash]) == null)
 626             tab[i] = newNode(hash, key, value, null);
 627         else {
 628             Node<K,V> e; K k;
 629             if (p.hash == hash &&
 630                 ((k = p.key) == key || (key != null && key.equals(k))))
 631                 e = p;
 632             else if (p instanceof TreeNode)
 633                 e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
 634             else {
 635                 for (int binCount = 0; ; ++binCount) {
 636                     if ((e = p.next) == null) {
 637                         p.next = newNode(hash, key, value, null);
 638                         if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
 639                             treeifyBin(tab, hash);
 640                         break;
 641                     }
 642                     if (e.hash == hash &&
 643                         ((k = e.key) == key || (key != null && key.equals(k))))
 644                         break;
 645                     p = e;
 646                 }
 647             }
 648             if (e != null) { // existing mapping for key
 649                 V oldValue = e.value;
 650                 if (!onlyIfAbsent || oldValue == null)
 651                     e.value = value;
 652                 afterNodeAccess(e);
 653                 return oldValue;
 654             }
 655         }
 656         ++modCount;
 657         if (++size > threshold)
 658             resize();
 659         afterNodeInsertion(evict);
 660         return null;
 661     }
 662 
 663     /**
 664      * Initializes or doubles table size.  If null, allocates in
 665      * accord with initial capacity target held in field threshold.
 666      * Otherwise, because we are using power-of-two expansion, the
 667      * elements from each bin must either stay at same index, or move
 668      * with a power of two offset in the new table.
 669      *
 670      * @return the table
 671      */
 672     final Node<K,V>[] resize() {
 673         Node<K,V>[] oldTab = table;
 674         int oldCap = (oldTab == null) ? 0 : oldTab.length;
 675         int oldThr = threshold;
 676         int newCap, newThr = 0;
 677         if (oldCap > 0) {
 678             if (oldCap >= MAXIMUM_CAPACITY) {
 679                 threshold = Integer.MAX_VALUE;
 680                 return oldTab;
 681             }
 682             else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY &&
 683                      oldCap >= DEFAULT_INITIAL_CAPACITY)
 684                 newThr = oldThr << 1; // double threshold
 685         }
 686         else if (oldThr > 0) // initial capacity was placed in threshold
 687             newCap = oldThr;
 688         else {               // zero initial threshold signifies using defaults
 689             newCap = DEFAULT_INITIAL_CAPACITY;
 690             newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY);
 691         }
 692         if (newThr == 0) {
 693             float ft = (float)newCap * loadFactor;
 694             newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ?
 695                       (int)ft : Integer.MAX_VALUE);
 696         }
 697         threshold = newThr;
 698         @SuppressWarnings({"rawtypes","unchecked"})
 699         Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap];
 700         table = newTab;
 701         if (oldTab != null) {
 702             for (int j = 0; j < oldCap; ++j) {
 703                 Node<K,V> e;
 704                 if ((e = oldTab[j]) != null) {
 705                     oldTab[j] = null;
 706                     if (e.next == null)
 707                         newTab[e.hash & (newCap - 1)] = e;
 708                     else if (e instanceof TreeNode)
 709                         ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
 710                     else { // preserve order
 711                         Node<K,V> loHead = null, loTail = null;
 712                         Node<K,V> hiHead = null, hiTail = null;
 713                         Node<K,V> next;
 714                         do {
 715                             next = e.next;
 716                             if ((e.hash & oldCap) == 0) {
 717                                 if (loTail == null)
 718                                     loHead = e;
 719                                 else
 720                                     loTail.next = e;
 721                                 loTail = e;
 722                             }
 723                             else {
 724                                 if (hiTail == null)
 725                                     hiHead = e;
 726                                 else
 727                                     hiTail.next = e;
 728                                 hiTail = e;
 729                             }
 730                         } while ((e = next) != null);
 731                         if (loTail != null) {
 732                             loTail.next = null;
 733                             newTab[j] = loHead;
 734                         }
 735                         if (hiTail != null) {
 736                             hiTail.next = null;
 737                             newTab[j + oldCap] = hiHead;
 738                         }
 739                     }
 740                 }
 741             }
 742         }
 743         return newTab;
 744     }
 745 
 746     /**
 747      * Replaces all linked nodes in bin at index for given hash unless
 748      * table is too small, in which case resizes instead.
 749      */
 750     final void treeifyBin(Node<K,V>[] tab, int hash) {
 751         int n, index; Node<K,V> e;
 752         if (tab == null || (n = tab.length) < MIN_TREEIFY_CAPACITY)
 753             resize();
 754         else if ((e = tab[index = (n - 1) & hash]) != null) {
 755             TreeNode<K,V> hd = null, tl = null;
 756             do {
 757                 TreeNode<K,V> p = replacementTreeNode(e, null);
 758                 if (tl == null)
 759                     hd = p;
 760                 else {
 761                     p.prev = tl;
 762                     tl.next = p;
 763                 }
 764                 tl = p;
 765             } while ((e = e.next) != null);
 766             if ((tab[index] = hd) != null)
 767                 hd.treeify(tab);
 768         }
 769     }
 770 
 771     /**
 772      * Copies all of the mappings from the specified map to this map.
 773      * These mappings will replace any mappings that this map had for
 774      * any of the keys currently in the specified map.
 775      *
 776      * @param m mappings to be stored in this map
 777      * @throws NullPointerException if the specified map is null
 778      */
 779     public void putAll(Map<? extends K, ? extends V> m) {
 780         putMapEntries(m, true);
 781     }
 782 
 783     /**
 784      * Removes the mapping for the specified key from this map if present.
 785      *
 786      * @param  key key whose mapping is to be removed from the map
 787      * @return the previous value associated with {@code key}, or
 788      *         {@code null} if there was no mapping for {@code key}.
 789      *         (A {@code null} return can also indicate that the map
 790      *         previously associated {@code null} with {@code key}.)
 791      */
 792     public V remove(Object key) {
 793         Node<K,V> e;
 794         return (e = removeNode(hash(key), key, null, false, true)) == null ?
 795             null : e.value;
 796     }
 797 
 798     /**
 799      * Implements Map.remove and related methods.
 800      *
 801      * @param hash hash for key
 802      * @param key the key
 803      * @param value the value to match if matchValue, else ignored
 804      * @param matchValue if true only remove if value is equal
 805      * @param movable if false do not move other nodes while removing
 806      * @return the node, or null if none
 807      */
 808     final Node<K,V> removeNode(int hash, Object key, Object value,
 809                                boolean matchValue, boolean movable) {
 810         Node<K,V>[] tab; Node<K,V> p; int n, index;
 811         if ((tab = table) != null && (n = tab.length) > 0 &&
 812             (p = tab[index = (n - 1) & hash]) != null) {
 813             Node<K,V> node = null, e; K k; V v;
 814             if (p.hash == hash &&
 815                 ((k = p.key) == key || (key != null && key.equals(k))))
 816                 node = p;
 817             else if ((e = p.next) != null) {
 818                 if (p instanceof TreeNode)
 819                     node = ((TreeNode<K,V>)p).getTreeNode(hash, key);
 820                 else {
 821                     do {
 822                         if (e.hash == hash &&
 823                             ((k = e.key) == key ||
 824                              (key != null && key.equals(k)))) {
 825                             node = e;
 826                             break;
 827                         }
 828                         p = e;
 829                     } while ((e = e.next) != null);
 830                 }
 831             }
 832             if (node != null && (!matchValue || (v = node.value) == value ||
 833                                  (value != null && value.equals(v)))) {
 834                 if (node instanceof TreeNode)
 835                     ((TreeNode<K,V>)node).removeTreeNode(this, tab, movable);
 836                 else if (node == p)
 837                     tab[index] = node.next;
 838                 else
 839                     p.next = node.next;
 840                 ++modCount;
 841                 --size;
 842                 afterNodeRemoval(node);
 843                 return node;
 844             }
 845         }
 846         return null;
 847     }
 848 
 849     /**
 850      * Removes all of the mappings from this map.
 851      * The map will be empty after this call returns.
 852      */
 853     public void clear() {
 854         Node<K,V>[] tab;
 855         modCount++;
 856         if ((tab = table) != null && size > 0) {
 857             size = 0;
 858             for (int i = 0; i < tab.length; ++i)
 859                 tab[i] = null;
 860         }
 861     }
 862 
 863     /**
 864      * Returns {@code true} if this map maps one or more keys to the
 865      * specified value.
 866      *
 867      * @param value value whose presence in this map is to be tested
 868      * @return {@code true} if this map maps one or more keys to the
 869      *         specified value
 870      */
 871     public boolean containsValue(Object value) {
 872         Node<K,V>[] tab; V v;
 873         if ((tab = table) != null && size > 0) {
 874             for (Node<K,V> e : tab) {
 875                 for (; e != null; e = e.next) {
 876                     if ((v = e.value) == value ||
 877                         (value != null && value.equals(v)))
 878                         return true;
 879                 }
 880             }
 881         }
 882         return false;
 883     }
 884 
 885     /**
 886      * Returns a {@link Set} view of the keys contained in this map.
 887      * The set is backed by the map, so changes to the map are
 888      * reflected in the set, and vice-versa.  If the map is modified
 889      * while an iteration over the set is in progress (except through
 890      * the iterator's own {@code remove} operation), the results of
 891      * the iteration are undefined.  The set supports element removal,
 892      * which removes the corresponding mapping from the map, via the
 893      * {@code Iterator.remove}, {@code Set.remove},
 894      * {@code removeAll}, {@code retainAll}, and {@code clear}
 895      * operations.  It does not support the {@code add} or {@code addAll}
 896      * operations.
 897      *
 898      * @return a set view of the keys contained in this map
 899      */
 900     public Set<K> keySet() {
 901         Set<K> ks = keySet;
 902         if (ks == null) {
 903             ks = new KeySet();
 904             keySet = ks;
 905         }
 906         return ks;
 907     }
 908 
 909     final class KeySet extends AbstractSet<K> {
 910         public final int size()                 { return size; }
 911         public final void clear()               { HashMap.this.clear(); }
 912         public final Iterator<K> iterator()     { return new KeyIterator(); }
 913         public final boolean contains(Object o) { return containsKey(o); }
 914         public final boolean remove(Object key) {
 915             return removeNode(hash(key), key, null, false, true) != null;
 916         }
 917         public final Spliterator<K> spliterator() {
 918             return new KeySpliterator<>(HashMap.this, 0, -1, 0, 0);
 919         }
 920         public final void forEach(Consumer<? super K> action) {
 921             Node<K,V>[] tab;
 922             if (action == null)
 923                 throw new NullPointerException();
 924             if (size > 0 && (tab = table) != null) {
 925                 int mc = modCount;
 926                 for (Node<K,V> e : tab) {
 927                     for (; e != null; e = e.next)
 928                         action.accept(e.key);
 929                 }
 930                 if (modCount != mc)
 931                     throw new ConcurrentModificationException();
 932             }
 933         }
 934     }
 935 
 936     /**
 937      * Returns a {@link Collection} view of the values contained in this map.
 938      * The collection is backed by the map, so changes to the map are
 939      * reflected in the collection, and vice-versa.  If the map is
 940      * modified while an iteration over the collection is in progress
 941      * (except through the iterator's own {@code remove} operation),
 942      * the results of the iteration are undefined.  The collection
 943      * supports element removal, which removes the corresponding
 944      * mapping from the map, via the {@code Iterator.remove},
 945      * {@code Collection.remove}, {@code removeAll},
 946      * {@code retainAll} and {@code clear} operations.  It does not
 947      * support the {@code add} or {@code addAll} operations.
 948      *
 949      * @return a view of the values contained in this map
 950      */
 951     public Collection<V> values() {
 952         Collection<V> vs = values;
 953         if (vs == null) {
 954             vs = new Values();
 955             values = vs;
 956         }
 957         return vs;
 958     }
 959 
 960     final class Values extends AbstractCollection<V> {
 961         public final int size()                 { return size; }
 962         public final void clear()               { HashMap.this.clear(); }
 963         public final Iterator<V> iterator()     { return new ValueIterator(); }
 964         public final boolean contains(Object o) { return containsValue(o); }
 965         public final Spliterator<V> spliterator() {
 966             return new ValueSpliterator<>(HashMap.this, 0, -1, 0, 0);
 967         }
 968         public final void forEach(Consumer<? super V> action) {
 969             Node<K,V>[] tab;
 970             if (action == null)
 971                 throw new NullPointerException();
 972             if (size > 0 && (tab = table) != null) {
 973                 int mc = modCount;
 974                 for (Node<K,V> e : tab) {
 975                     for (; e != null; e = e.next)
 976                         action.accept(e.value);
 977                 }
 978                 if (modCount != mc)
 979                     throw new ConcurrentModificationException();
 980             }
 981         }
 982     }
 983 
 984     /**
 985      * Returns a {@link Set} view of the mappings contained in this map.
 986      * The set is backed by the map, so changes to the map are
 987      * reflected in the set, and vice-versa.  If the map is modified
 988      * while an iteration over the set is in progress (except through
 989      * the iterator's own {@code remove} operation, or through the
 990      * {@code setValue} operation on a map entry returned by the
 991      * iterator) the results of the iteration are undefined.  The set
 992      * supports element removal, which removes the corresponding
 993      * mapping from the map, via the {@code Iterator.remove},
 994      * {@code Set.remove}, {@code removeAll}, {@code retainAll} and
 995      * {@code clear} operations.  It does not support the
 996      * {@code add} or {@code addAll} operations.
 997      *
 998      * @return a set view of the mappings contained in this map
 999      */
1000     public Set<Map.Entry<K,V>> entrySet() {
1001         Set<Map.Entry<K,V>> es;
1002         return (es = entrySet) == null ? (entrySet = new EntrySet()) : es;
1003     }
1004 
1005     final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
1006         public final int size()                 { return size; }
1007         public final void clear()               { HashMap.this.clear(); }
1008         public final Iterator<Map.Entry<K,V>> iterator() {
1009             return new EntryIterator();
1010         }
1011         public final boolean contains(Object o) {
1012             if (!(o instanceof Map.Entry))
1013                 return false;
1014             Map.Entry<?,?> e = (Map.Entry<?,?>) o;
1015             Object key = e.getKey();
1016             Node<K,V> candidate = getNode(hash(key), key);
1017             return candidate != null && candidate.equals(e);
1018         }
1019         public final boolean remove(Object o) {
1020             if (o instanceof Map.Entry) {
1021                 Map.Entry<?,?> e = (Map.Entry<?,?>) o;
1022                 Object key = e.getKey();
1023                 Object value = e.getValue();
1024                 return removeNode(hash(key), key, value, true, true) != null;
1025             }
1026             return false;
1027         }
1028         public final Spliterator<Map.Entry<K,V>> spliterator() {
1029             return new EntrySpliterator<>(HashMap.this, 0, -1, 0, 0);
1030         }
1031         public final void forEach(Consumer<? super Map.Entry<K,V>> action) {
1032             Node<K,V>[] tab;
1033             if (action == null)
1034                 throw new NullPointerException();
1035             if (size > 0 && (tab = table) != null) {
1036                 int mc = modCount;
1037                 for (Node<K,V> e : tab) {
1038                     for (; e != null; e = e.next)
1039                         action.accept(e);
1040                 }
1041                 if (modCount != mc)
1042                     throw new ConcurrentModificationException();
1043             }
1044         }
1045     }
1046 
1047     // Overrides of JDK8 Map extension methods
1048 
1049     @Override
1050     public V getOrDefault(Object key, V defaultValue) {
1051         Node<K,V> e;
1052         return (e = getNode(hash(key), key)) == null ? defaultValue : e.value;
1053     }
1054 
1055     @Override
1056     public V putIfAbsent(K key, V value) {
1057         return putVal(hash(key), key, value, true, true);
1058     }
1059 
1060     @Override
1061     public boolean remove(Object key, Object value) {
1062         return removeNode(hash(key), key, value, true, true) != null;
1063     }
1064 
1065     @Override
1066     public boolean replace(K key, V oldValue, V newValue) {
1067         Node<K,V> e; V v;
1068         if ((e = getNode(hash(key), key)) != null &&
1069             ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
1070             e.value = newValue;
1071             afterNodeAccess(e);
1072             return true;
1073         }
1074         return false;
1075     }
1076 
1077     @Override
1078     public V replace(K key, V value) {
1079         Node<K,V> e;
1080         if ((e = getNode(hash(key), key)) != null) {
1081             V oldValue = e.value;
1082             e.value = value;
1083             afterNodeAccess(e);
1084             return oldValue;
1085         }
1086         return null;
1087     }
1088 
1089     /**
1090      * {@inheritDoc}
1091      *
1092      * <p>This method will, on a best-effort basis, throw a
1093      * {@link ConcurrentModificationException} if it is detected that the
1094      * mapping function modifies this map during computation.
1095      *
1096      * @throws ConcurrentModificationException if it is detected that the
1097      * mapping function modified this map
1098      */
1099     @Override
1100     public V computeIfAbsent(K key,
1101                              Function<? super K, ? extends V> mappingFunction) {
1102         if (mappingFunction == null)
1103             throw new NullPointerException();
1104         int hash = hash(key);
1105         Node<K,V>[] tab; Node<K,V> first; int n, i;
1106         int binCount = 0;
1107         TreeNode<K,V> t = null;
1108         Node<K,V> old = null;
1109         if (size > threshold || (tab = table) == null ||
1110             (n = tab.length) == 0)
1111             n = (tab = resize()).length;
1112         if ((first = tab[i = (n - 1) & hash]) != null) {
1113             if (first instanceof TreeNode)
1114                 old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
1115             else {
1116                 Node<K,V> e = first; K k;
1117                 do {
1118                     if (e.hash == hash &&
1119                         ((k = e.key) == key || (key != null && key.equals(k)))) {
1120                         old = e;
1121                         break;
1122                     }
1123                     ++binCount;
1124                 } while ((e = e.next) != null);
1125             }
1126             V oldValue;
1127             if (old != null && (oldValue = old.value) != null) {
1128                 afterNodeAccess(old);
1129                 return oldValue;
1130             }
1131         }
1132         int mc = modCount;
1133         V v = mappingFunction.apply(key);
1134         if (mc != modCount) { throw new ConcurrentModificationException(); }
1135         if (v == null) {
1136             return null;
1137         } else if (old != null) {
1138             old.value = v;
1139             afterNodeAccess(old);
1140             return v;
1141         }
1142         else if (t != null)
1143             t.putTreeVal(this, tab, hash, key, v);
1144         else {
1145             tab[i] = newNode(hash, key, v, first);
1146             if (binCount >= TREEIFY_THRESHOLD - 1)
1147                 treeifyBin(tab, hash);
1148         }
1149         modCount = mc + 1;
1150         ++size;
1151         afterNodeInsertion(true);
1152         return v;
1153     }
1154 
1155     /**
1156      * {@inheritDoc}
1157      *
1158      * <p>This method will, on a best-effort basis, throw a
1159      * {@link ConcurrentModificationException} if it is detected that the
1160      * remapping function modifies this map during computation.
1161      *
1162      * @throws ConcurrentModificationException if it is detected that the
1163      * remapping function modified this map
1164      */
1165     @Override
1166     public V computeIfPresent(K key,
1167                               BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1168         if (remappingFunction == null)
1169             throw new NullPointerException();
1170         Node<K,V> e; V oldValue;
1171         int hash = hash(key);
1172         if ((e = getNode(hash, key)) != null &&
1173             (oldValue = e.value) != null) {
1174             int mc = modCount;
1175             V v = remappingFunction.apply(key, oldValue);
1176             if (mc != modCount) { throw new ConcurrentModificationException(); }
1177             if (v != null) {
1178                 e.value = v;
1179                 afterNodeAccess(e);
1180                 return v;
1181             }
1182             else
1183                 removeNode(hash, key, null, false, true);
1184         }
1185         return null;
1186     }
1187 
1188     /**
1189      * {@inheritDoc}
1190      *
1191      * <p>This method will, on a best-effort basis, throw a
1192      * {@link ConcurrentModificationException} if it is detected that the
1193      * remapping function modifies this map during computation.
1194      *
1195      * @throws ConcurrentModificationException if it is detected that the
1196      * remapping function modified this map
1197      */
1198     @Override
1199     public V compute(K key,
1200                      BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
1201         if (remappingFunction == null)
1202             throw new NullPointerException();
1203         int hash = hash(key);
1204         Node<K,V>[] tab; Node<K,V> first; int n, i;
1205         int binCount = 0;
1206         TreeNode<K,V> t = null;
1207         Node<K,V> old = null;
1208         if (size > threshold || (tab = table) == null ||
1209             (n = tab.length) == 0)
1210             n = (tab = resize()).length;
1211         if ((first = tab[i = (n - 1) & hash]) != null) {
1212             if (first instanceof TreeNode)
1213                 old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
1214             else {
1215                 Node<K,V> e = first; K k;
1216                 do {
1217                     if (e.hash == hash &&
1218                         ((k = e.key) == key || (key != null && key.equals(k)))) {
1219                         old = e;
1220                         break;
1221                     }
1222                     ++binCount;
1223                 } while ((e = e.next) != null);
1224             }
1225         }
1226         V oldValue = (old == null) ? null : old.value;
1227         int mc = modCount;
1228         V v = remappingFunction.apply(key, oldValue);
1229         if (mc != modCount) { throw new ConcurrentModificationException(); }
1230         if (old != null) {
1231             if (v != null) {
1232                 old.value = v;
1233                 afterNodeAccess(old);
1234             }
1235             else
1236                 removeNode(hash, key, null, false, true);
1237         }
1238         else if (v != null) {
1239             if (t != null)
1240                 t.putTreeVal(this, tab, hash, key, v);
1241             else {
1242                 tab[i] = newNode(hash, key, v, first);
1243                 if (binCount >= TREEIFY_THRESHOLD - 1)
1244                     treeifyBin(tab, hash);
1245             }
1246             modCount = mc + 1;
1247             ++size;
1248             afterNodeInsertion(true);
1249         }
1250         return v;
1251     }
1252 
1253     /**
1254      * {@inheritDoc}
1255      *
1256      * <p>This method will, on a best-effort basis, throw a
1257      * {@link ConcurrentModificationException} if it is detected that the
1258      * remapping function modifies this map during computation.
1259      *
1260      * @throws ConcurrentModificationException if it is detected that the
1261      * remapping function modified this map
1262      */
1263     @Override
1264     public V merge(K key, V value,
1265                    BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
1266         if (value == null || remappingFunction == null)
1267             throw new NullPointerException();
1268         int hash = hash(key);
1269         Node<K,V>[] tab; Node<K,V> first; int n, i;
1270         int binCount = 0;
1271         TreeNode<K,V> t = null;
1272         Node<K,V> old = null;
1273         if (size > threshold || (tab = table) == null ||
1274             (n = tab.length) == 0)
1275             n = (tab = resize()).length;
1276         if ((first = tab[i = (n - 1) & hash]) != null) {
1277             if (first instanceof TreeNode)
1278                 old = (t = (TreeNode<K,V>)first).getTreeNode(hash, key);
1279             else {
1280                 Node<K,V> e = first; K k;
1281                 do {
1282                     if (e.hash == hash &&
1283                         ((k = e.key) == key || (key != null && key.equals(k)))) {
1284                         old = e;
1285                         break;
1286                     }
1287                     ++binCount;
1288                 } while ((e = e.next) != null);
1289             }
1290         }
1291         if (old != null) {
1292             V v;
1293             if (old.value != null) {
1294                 int mc = modCount;
1295                 v = remappingFunction.apply(old.value, value);
1296                 if (mc != modCount) {
1297                     throw new ConcurrentModificationException();
1298                 }
1299             } else {
1300                 v = value;
1301             }
1302             if (v != null) {
1303                 old.value = v;
1304                 afterNodeAccess(old);
1305             }
1306             else
1307                 removeNode(hash, key, null, false, true);
1308             return v;
1309         } else {
1310             if (t != null)
1311                 t.putTreeVal(this, tab, hash, key, value);
1312             else {
1313                 tab[i] = newNode(hash, key, value, first);
1314                 if (binCount >= TREEIFY_THRESHOLD - 1)
1315                     treeifyBin(tab, hash);
1316             }
1317             ++modCount;
1318             ++size;
1319             afterNodeInsertion(true);
1320             return value;
1321         }
1322     }
1323 
1324     @Override
1325     public void forEach(BiConsumer<? super K, ? super V> action) {
1326         Node<K,V>[] tab;
1327         if (action == null)
1328             throw new NullPointerException();
1329         if (size > 0 && (tab = table) != null) {
1330             int mc = modCount;
1331             for (Node<K,V> e : tab) {
1332                 for (; e != null; e = e.next)
1333                     action.accept(e.key, e.value);
1334             }
1335             if (modCount != mc)
1336                 throw new ConcurrentModificationException();
1337         }
1338     }
1339 
1340     @Override
1341     public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
1342         Node<K,V>[] tab;
1343         if (function == null)
1344             throw new NullPointerException();
1345         if (size > 0 && (tab = table) != null) {
1346             int mc = modCount;
1347             for (Node<K,V> e : tab) {
1348                 for (; e != null; e = e.next) {
1349                     e.value = function.apply(e.key, e.value);
1350                 }
1351             }
1352             if (modCount != mc)
1353                 throw new ConcurrentModificationException();
1354         }
1355     }
1356 
1357     /* ------------------------------------------------------------ */
1358     // Cloning and serialization
1359 
1360     /**
1361      * Returns a shallow copy of this {@code HashMap} instance: the keys and
1362      * values themselves are not cloned.
1363      *
1364      * @return a shallow copy of this map
1365      */
1366     @SuppressWarnings("unchecked")
1367     @Override
1368     public Object clone() {
1369         HashMap<K,V> result;
1370         try {
1371             result = (HashMap<K,V>)super.clone();
1372         } catch (CloneNotSupportedException e) {
1373             // this shouldn't happen, since we are Cloneable
1374             throw new InternalError(e);
1375         }
1376         result.reinitialize();
1377         result.putMapEntries(this, false);
1378         return result;
1379     }
1380 
1381     // These methods are also used when serializing HashSets
1382     final float loadFactor() { return loadFactor; }
1383     final int capacity() {
1384         return (table != null) ? table.length :
1385             (threshold > 0) ? threshold :
1386             DEFAULT_INITIAL_CAPACITY;
1387     }
1388 
1389     /**
1390      * Saves this map to a stream (that is, serializes it).
1391      *
1392      * @param s the stream
1393      * @throws IOException if an I/O error occurs
1394      * @serialData The <i>capacity</i> of the HashMap (the length of the
1395      *             bucket array) is emitted (int), followed by the
1396      *             <i>size</i> (an int, the number of key-value
1397      *             mappings), followed by the key (Object) and value (Object)
1398      *             for each key-value mapping.  The key-value mappings are
1399      *             emitted in no particular order.
1400      */
1401     private void writeObject(java.io.ObjectOutputStream s)
1402         throws IOException {
1403         int buckets = capacity();
1404         // Write out the threshold, loadfactor, and any hidden stuff
1405         s.defaultWriteObject();
1406         s.writeInt(buckets);
1407         s.writeInt(size);
1408         internalWriteEntries(s);
1409     }
1410 
1411     /**
1412      * Reconstitutes this map from a stream (that is, deserializes it).
1413      * @param s the stream
1414      * @throws ClassNotFoundException if the class of a serialized object
1415      *         could not be found
1416      * @throws IOException if an I/O error occurs
1417      */
1418     private void readObject(java.io.ObjectInputStream s)
1419         throws IOException, ClassNotFoundException {
1420         // Read in the threshold (ignored), loadfactor, and any hidden stuff
1421         s.defaultReadObject();
1422         reinitialize();
1423         if (!(loadFactor > 0))          // also checks for NaNs
1424             throw new InvalidObjectException("Illegal load factor: " +
1425                                              loadFactor);
1426         s.readInt();                // Read and ignore number of buckets
1427         int mappings = s.readInt(); // Read number of mappings (size)
1428         if (mappings < 0)
1429             throw new InvalidObjectException("Illegal mappings count: " +
1430                                              mappings);
1431         else if (mappings > 0) { // (if zero, use defaults)
1432             // Size the table using given load factor only if within
1433             // range of 0.25...4.0
1434             float lf = Math.min(Math.max(0.25f, loadFactor), 4.0f);
1435             float fc = (float)mappings / lf + 1.0f;
1436             int cap = ((fc < DEFAULT_INITIAL_CAPACITY) ?
1437                        DEFAULT_INITIAL_CAPACITY :
1438                        (fc >= MAXIMUM_CAPACITY) ?
1439                        MAXIMUM_CAPACITY :
1440                        tableSizeFor((int)fc));
1441             float ft = (float)cap * lf;
1442             threshold = ((cap < MAXIMUM_CAPACITY && ft < MAXIMUM_CAPACITY) ?
1443                          (int)ft : Integer.MAX_VALUE);
1444 
1445             // Check Map.Entry[].class since it's the nearest public type to
1446             // what we're actually creating.
1447             SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Map.Entry[].class, cap);
1448             @SuppressWarnings({"rawtypes","unchecked"})
1449             Node<K,V>[] tab = (Node<K,V>[])new Node[cap];
1450             table = tab;
1451 
1452             // Read the keys and values, and put the mappings in the HashMap
1453             for (int i = 0; i < mappings; i++) {
1454                 @SuppressWarnings("unchecked")
1455                     K key = (K) s.readObject();
1456                 @SuppressWarnings("unchecked")
1457                     V value = (V) s.readObject();
1458                 putVal(hash(key), key, value, false, false);
1459             }
1460         }
1461     }
1462 
1463     /* ------------------------------------------------------------ */
1464     // iterators
1465 
1466     abstract class HashIterator {
1467         Node<K,V> next;        // next entry to return
1468         Node<K,V> current;     // current entry
1469         int expectedModCount;  // for fast-fail
1470         int index;             // current slot
1471 
1472         HashIterator() {
1473             expectedModCount = modCount;
1474             Node<K,V>[] t = table;
1475             current = next = null;
1476             index = 0;
1477             if (t != null && size > 0) { // advance to first entry
1478                 do {} while (index < t.length && (next = t[index++]) == null);
1479             }
1480         }
1481 
1482         public final boolean hasNext() {
1483             return next != null;
1484         }
1485 
1486         final Node<K,V> nextNode() {
1487             Node<K,V>[] t;
1488             Node<K,V> e = next;
1489             if (modCount != expectedModCount)
1490                 throw new ConcurrentModificationException();
1491             if (e == null)
1492                 throw new NoSuchElementException();
1493             if ((next = (current = e).next) == null && (t = table) != null) {
1494                 do {} while (index < t.length && (next = t[index++]) == null);
1495             }
1496             return e;
1497         }
1498 
1499         public final void remove() {
1500             Node<K,V> p = current;
1501             if (p == null)
1502                 throw new IllegalStateException();
1503             if (modCount != expectedModCount)
1504                 throw new ConcurrentModificationException();
1505             current = null;
1506             removeNode(p.hash, p.key, null, false, false);
1507             expectedModCount = modCount;
1508         }
1509     }
1510 
1511     final class KeyIterator extends HashIterator
1512         implements Iterator<K> {
1513         public final K next() { return nextNode().key; }
1514     }
1515 
1516     final class ValueIterator extends HashIterator
1517         implements Iterator<V> {
1518         public final V next() { return nextNode().value; }
1519     }
1520 
1521     final class EntryIterator extends HashIterator
1522         implements Iterator<Map.Entry<K,V>> {
1523         public final Map.Entry<K,V> next() { return nextNode(); }
1524     }
1525 
1526     /* ------------------------------------------------------------ */
1527     // spliterators
1528 
1529     static class HashMapSpliterator<K,V> {
1530         final HashMap<K,V> map;
1531         Node<K,V> current;          // current node
1532         int index;                  // current index, modified on advance/split
1533         int fence;                  // one past last index
1534         int est;                    // size estimate
1535         int expectedModCount;       // for comodification checks
1536 
1537         HashMapSpliterator(HashMap<K,V> m, int origin,
1538                            int fence, int est,
1539                            int expectedModCount) {
1540             this.map = m;
1541             this.index = origin;
1542             this.fence = fence;
1543             this.est = est;
1544             this.expectedModCount = expectedModCount;
1545         }
1546 
1547         final int getFence() { // initialize fence and size on first use
1548             int hi;
1549             if ((hi = fence) < 0) {
1550                 HashMap<K,V> m = map;
1551                 est = m.size;
1552                 expectedModCount = m.modCount;
1553                 Node<K,V>[] tab = m.table;
1554                 hi = fence = (tab == null) ? 0 : tab.length;
1555             }
1556             return hi;
1557         }
1558 
1559         public final long estimateSize() {
1560             getFence(); // force init
1561             return (long) est;
1562         }
1563     }
1564 
1565     static final class KeySpliterator<K,V>
1566         extends HashMapSpliterator<K,V>
1567         implements Spliterator<K> {
1568         KeySpliterator(HashMap<K,V> m, int origin, int fence, int est,
1569                        int expectedModCount) {
1570             super(m, origin, fence, est, expectedModCount);
1571         }
1572 
1573         public KeySpliterator<K,V> trySplit() {
1574             int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1575             return (lo >= mid || current != null) ? null :
1576                 new KeySpliterator<>(map, lo, index = mid, est >>>= 1,
1577                                         expectedModCount);
1578         }
1579 
1580         public void forEachRemaining(Consumer<? super K> action) {
1581             int i, hi, mc;
1582             if (action == null)
1583                 throw new NullPointerException();
1584             HashMap<K,V> m = map;
1585             Node<K,V>[] tab = m.table;
1586             if ((hi = fence) < 0) {
1587                 mc = expectedModCount = m.modCount;
1588                 hi = fence = (tab == null) ? 0 : tab.length;
1589             }
1590             else
1591                 mc = expectedModCount;
1592             if (tab != null && tab.length >= hi &&
1593                 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1594                 Node<K,V> p = current;
1595                 current = null;
1596                 do {
1597                     if (p == null)
1598                         p = tab[i++];
1599                     else {
1600                         action.accept(p.key);
1601                         p = p.next;
1602                     }
1603                 } while (p != null || i < hi);
1604                 if (m.modCount != mc)
1605                     throw new ConcurrentModificationException();
1606             }
1607         }
1608 
1609         public boolean tryAdvance(Consumer<? super K> action) {
1610             int hi;
1611             if (action == null)
1612                 throw new NullPointerException();
1613             Node<K,V>[] tab = map.table;
1614             if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1615                 while (current != null || index < hi) {
1616                     if (current == null)
1617                         current = tab[index++];
1618                     else {
1619                         K k = current.key;
1620                         current = current.next;
1621                         action.accept(k);
1622                         if (map.modCount != expectedModCount)
1623                             throw new ConcurrentModificationException();
1624                         return true;
1625                     }
1626                 }
1627             }
1628             return false;
1629         }
1630 
1631         public int characteristics() {
1632             return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
1633                 Spliterator.DISTINCT;
1634         }
1635     }
1636 
1637     static final class ValueSpliterator<K,V>
1638         extends HashMapSpliterator<K,V>
1639         implements Spliterator<V> {
1640         ValueSpliterator(HashMap<K,V> m, int origin, int fence, int est,
1641                          int expectedModCount) {
1642             super(m, origin, fence, est, expectedModCount);
1643         }
1644 
1645         public ValueSpliterator<K,V> trySplit() {
1646             int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1647             return (lo >= mid || current != null) ? null :
1648                 new ValueSpliterator<>(map, lo, index = mid, est >>>= 1,
1649                                           expectedModCount);
1650         }
1651 
1652         public void forEachRemaining(Consumer<? super V> action) {
1653             int i, hi, mc;
1654             if (action == null)
1655                 throw new NullPointerException();
1656             HashMap<K,V> m = map;
1657             Node<K,V>[] tab = m.table;
1658             if ((hi = fence) < 0) {
1659                 mc = expectedModCount = m.modCount;
1660                 hi = fence = (tab == null) ? 0 : tab.length;
1661             }
1662             else
1663                 mc = expectedModCount;
1664             if (tab != null && tab.length >= hi &&
1665                 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1666                 Node<K,V> p = current;
1667                 current = null;
1668                 do {
1669                     if (p == null)
1670                         p = tab[i++];
1671                     else {
1672                         action.accept(p.value);
1673                         p = p.next;
1674                     }
1675                 } while (p != null || i < hi);
1676                 if (m.modCount != mc)
1677                     throw new ConcurrentModificationException();
1678             }
1679         }
1680 
1681         public boolean tryAdvance(Consumer<? super V> action) {
1682             int hi;
1683             if (action == null)
1684                 throw new NullPointerException();
1685             Node<K,V>[] tab = map.table;
1686             if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1687                 while (current != null || index < hi) {
1688                     if (current == null)
1689                         current = tab[index++];
1690                     else {
1691                         V v = current.value;
1692                         current = current.next;
1693                         action.accept(v);
1694                         if (map.modCount != expectedModCount)
1695                             throw new ConcurrentModificationException();
1696                         return true;
1697                     }
1698                 }
1699             }
1700             return false;
1701         }
1702 
1703         public int characteristics() {
1704             return (fence < 0 || est == map.size ? Spliterator.SIZED : 0);
1705         }
1706     }
1707 
1708     static final class EntrySpliterator<K,V>
1709         extends HashMapSpliterator<K,V>
1710         implements Spliterator<Map.Entry<K,V>> {
1711         EntrySpliterator(HashMap<K,V> m, int origin, int fence, int est,
1712                          int expectedModCount) {
1713             super(m, origin, fence, est, expectedModCount);
1714         }
1715 
1716         public EntrySpliterator<K,V> trySplit() {
1717             int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
1718             return (lo >= mid || current != null) ? null :
1719                 new EntrySpliterator<>(map, lo, index = mid, est >>>= 1,
1720                                           expectedModCount);
1721         }
1722 
1723         public void forEachRemaining(Consumer<? super Map.Entry<K,V>> action) {
1724             int i, hi, mc;
1725             if (action == null)
1726                 throw new NullPointerException();
1727             HashMap<K,V> m = map;
1728             Node<K,V>[] tab = m.table;
1729             if ((hi = fence) < 0) {
1730                 mc = expectedModCount = m.modCount;
1731                 hi = fence = (tab == null) ? 0 : tab.length;
1732             }
1733             else
1734                 mc = expectedModCount;
1735             if (tab != null && tab.length >= hi &&
1736                 (i = index) >= 0 && (i < (index = hi) || current != null)) {
1737                 Node<K,V> p = current;
1738                 current = null;
1739                 do {
1740                     if (p == null)
1741                         p = tab[i++];
1742                     else {
1743                         action.accept(p);
1744                         p = p.next;
1745                     }
1746                 } while (p != null || i < hi);
1747                 if (m.modCount != mc)
1748                     throw new ConcurrentModificationException();
1749             }
1750         }
1751 
1752         public boolean tryAdvance(Consumer<? super Map.Entry<K,V>> action) {
1753             int hi;
1754             if (action == null)
1755                 throw new NullPointerException();
1756             Node<K,V>[] tab = map.table;
1757             if (tab != null && tab.length >= (hi = getFence()) && index >= 0) {
1758                 while (current != null || index < hi) {
1759                     if (current == null)
1760                         current = tab[index++];
1761                     else {
1762                         Node<K,V> e = current;
1763                         current = current.next;
1764                         action.accept(e);
1765                         if (map.modCount != expectedModCount)
1766                             throw new ConcurrentModificationException();
1767                         return true;
1768                     }
1769                 }
1770             }
1771             return false;
1772         }
1773 
1774         public int characteristics() {
1775             return (fence < 0 || est == map.size ? Spliterator.SIZED : 0) |
1776                 Spliterator.DISTINCT;
1777         }
1778     }
1779 
1780     /* ------------------------------------------------------------ */
1781     // LinkedHashMap support
1782 
1783 
1784     /*
1785      * The following package-protected methods are designed to be
1786      * overridden by LinkedHashMap, but not by any other subclass.
1787      * Nearly all other internal methods are also package-protected
1788      * but are declared final, so can be used by LinkedHashMap, view
1789      * classes, and HashSet.
1790      */
1791 
1792     // Create a regular (non-tree) node
1793     Node<K,V> newNode(int hash, K key, V value, Node<K,V> next) {
1794         return new Node<>(hash, key, value, next);
1795     }
1796 
1797     // For conversion from TreeNodes to plain nodes
1798     Node<K,V> replacementNode(Node<K,V> p, Node<K,V> next) {
1799         return new Node<>(p.hash, p.key, p.value, next);
1800     }
1801 
1802     // Create a tree bin node
1803     TreeNode<K,V> newTreeNode(int hash, K key, V value, Node<K,V> next) {
1804         return new TreeNode<>(hash, key, value, next);
1805     }
1806 
1807     // For treeifyBin
1808     TreeNode<K,V> replacementTreeNode(Node<K,V> p, Node<K,V> next) {
1809         return new TreeNode<>(p.hash, p.key, p.value, next);
1810     }
1811 
1812     /**
1813      * Reset to initial default state.  Called by clone and readObject.
1814      */
1815     void reinitialize() {
1816         table = null;
1817         entrySet = null;
1818         keySet = null;
1819         values = null;
1820         modCount = 0;
1821         threshold = 0;
1822         size = 0;
1823     }
1824 
1825     // Callbacks to allow LinkedHashMap post-actions
1826     void afterNodeAccess(Node<K,V> p) { }
1827     void afterNodeInsertion(boolean evict) { }
1828     void afterNodeRemoval(Node<K,V> p) { }
1829 
1830     // Called only from writeObject, to ensure compatible ordering.
1831     void internalWriteEntries(java.io.ObjectOutputStream s) throws IOException {
1832         Node<K,V>[] tab;
1833         if (size > 0 && (tab = table) != null) {
1834             for (Node<K,V> e : tab) {
1835                 for (; e != null; e = e.next) {
1836                     s.writeObject(e.key);
1837                     s.writeObject(e.value);
1838                 }
1839             }
1840         }
1841     }
1842 
1843     /* ------------------------------------------------------------ */
1844     // Tree bins
1845 
1846     /**
1847      * Entry for Tree bins. Extends LinkedHashMap.Entry (which in turn
1848      * extends Node) so can be used as extension of either regular or
1849      * linked node.
1850      */
1851     static final class TreeNode<K,V> extends LinkedHashMap.Entry<K,V> {
1852         TreeNode<K,V> parent;  // red-black tree links
1853         TreeNode<K,V> left;
1854         TreeNode<K,V> right;
1855         TreeNode<K,V> prev;    // needed to unlink next upon deletion
1856         boolean red;
1857         TreeNode(int hash, K key, V val, Node<K,V> next) {
1858             super(hash, key, val, next);
1859         }
1860 
1861         /**
1862          * Returns root of tree containing this node.
1863          */
1864         final TreeNode<K,V> root() {
1865             for (TreeNode<K,V> r = this, p;;) {
1866                 if ((p = r.parent) == null)
1867                     return r;
1868                 r = p;
1869             }
1870         }
1871 
1872         /**
1873          * Ensures that the given root is the first node of its bin.
1874          */
1875         static <K,V> void moveRootToFront(Node<K,V>[] tab, TreeNode<K,V> root) {
1876             int n;
1877             if (root != null && tab != null && (n = tab.length) > 0) {
1878                 int index = (n - 1) & root.hash;
1879                 TreeNode<K,V> first = (TreeNode<K,V>)tab[index];
1880                 if (root != first) {
1881                     Node<K,V> rn;
1882                     tab[index] = root;
1883                     TreeNode<K,V> rp = root.prev;
1884                     if ((rn = root.next) != null)
1885                         ((TreeNode<K,V>)rn).prev = rp;
1886                     if (rp != null)
1887                         rp.next = rn;
1888                     if (first != null)
1889                         first.prev = root;
1890                     root.next = first;
1891                     root.prev = null;
1892                 }
1893                 assert checkInvariants(root);
1894             }
1895         }
1896 
1897         /**
1898          * Finds the node starting at root p with the given hash and key.
1899          * The kc argument caches comparableClassFor(key) upon first use
1900          * comparing keys.
1901          */
1902         final TreeNode<K,V> find(int h, Object k, Class<?> kc) {
1903             TreeNode<K,V> p = this;
1904             do {
1905                 int ph, dir; K pk;
1906                 TreeNode<K,V> pl = p.left, pr = p.right, q;
1907                 if ((ph = p.hash) > h)
1908                     p = pl;
1909                 else if (ph < h)
1910                     p = pr;
1911                 else if ((pk = p.key) == k || (k != null && k.equals(pk)))
1912                     return p;
1913                 else if (pl == null)
1914                     p = pr;
1915                 else if (pr == null)
1916                     p = pl;
1917                 else if ((kc != null ||
1918                           (kc = comparableClassFor(k)) != null) &&
1919                          (dir = compareComparables(kc, k, pk)) != 0)
1920                     p = (dir < 0) ? pl : pr;
1921                 else if ((q = pr.find(h, k, kc)) != null)
1922                     return q;
1923                 else
1924                     p = pl;
1925             } while (p != null);
1926             return null;
1927         }
1928 
1929         /**
1930          * Calls find for root node.
1931          */
1932         final TreeNode<K,V> getTreeNode(int h, Object k) {
1933             return ((parent != null) ? root() : this).find(h, k, null);
1934         }
1935 
1936         /**
1937          * Tie-breaking utility for ordering insertions when equal
1938          * hashCodes and non-comparable. We don't require a total
1939          * order, just a consistent insertion rule to maintain
1940          * equivalence across rebalancings. Tie-breaking further than
1941          * necessary simplifies testing a bit.
1942          */
1943         static int tieBreakOrder(Object a, Object b) {
1944             int d;
1945             if (a == null || b == null ||
1946                 (d = a.getClass().getName().
1947                  compareTo(b.getClass().getName())) == 0)
1948                 d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
1949                      -1 : 1);
1950             return d;
1951         }
1952 
1953         /**
1954          * Forms tree of the nodes linked from this node.
1955          */
1956         final void treeify(Node<K,V>[] tab) {
1957             TreeNode<K,V> root = null;
1958             for (TreeNode<K,V> x = this, next; x != null; x = next) {
1959                 next = (TreeNode<K,V>)x.next;
1960                 x.left = x.right = null;
1961                 if (root == null) {
1962                     x.parent = null;
1963                     x.red = false;
1964                     root = x;
1965                 }
1966                 else {
1967                     K k = x.key;
1968                     int h = x.hash;
1969                     Class<?> kc = null;
1970                     for (TreeNode<K,V> p = root;;) {
1971                         int dir, ph;
1972                         K pk = p.key;
1973                         if ((ph = p.hash) > h)
1974                             dir = -1;
1975                         else if (ph < h)
1976                             dir = 1;
1977                         else if ((kc == null &&
1978                                   (kc = comparableClassFor(k)) == null) ||
1979                                  (dir = compareComparables(kc, k, pk)) == 0)
1980                             dir = tieBreakOrder(k, pk);
1981 
1982                         TreeNode<K,V> xp = p;
1983                         if ((p = (dir <= 0) ? p.left : p.right) == null) {
1984                             x.parent = xp;
1985                             if (dir <= 0)
1986                                 xp.left = x;
1987                             else
1988                                 xp.right = x;
1989                             root = balanceInsertion(root, x);
1990                             break;
1991                         }
1992                     }
1993                 }
1994             }
1995             moveRootToFront(tab, root);
1996         }
1997 
1998         /**
1999          * Returns a list of non-TreeNodes replacing those linked from
2000          * this node.
2001          */
2002         final Node<K,V> untreeify(HashMap<K,V> map) {
2003             Node<K,V> hd = null, tl = null;
2004             for (Node<K,V> q = this; q != null; q = q.next) {
2005                 Node<K,V> p = map.replacementNode(q, null);
2006                 if (tl == null)
2007                     hd = p;
2008                 else
2009                     tl.next = p;
2010                 tl = p;
2011             }
2012             return hd;
2013         }
2014 
2015         /**
2016          * Tree version of putVal.
2017          */
2018         final TreeNode<K,V> putTreeVal(HashMap<K,V> map, Node<K,V>[] tab,
2019                                        int h, K k, V v) {
2020             Class<?> kc = null;
2021             boolean searched = false;
2022             TreeNode<K,V> root = (parent != null) ? root() : this;
2023             for (TreeNode<K,V> p = root;;) {
2024                 int dir, ph; K pk;
2025                 if ((ph = p.hash) > h)
2026                     dir = -1;
2027                 else if (ph < h)
2028                     dir = 1;
2029                 else if ((pk = p.key) == k || (k != null && k.equals(pk)))
2030                     return p;
2031                 else if ((kc == null &&
2032                           (kc = comparableClassFor(k)) == null) ||
2033                          (dir = compareComparables(kc, k, pk)) == 0) {
2034                     if (!searched) {
2035                         TreeNode<K,V> q, ch;
2036                         searched = true;
2037                         if (((ch = p.left) != null &&
2038                              (q = ch.find(h, k, kc)) != null) ||
2039                             ((ch = p.right) != null &&
2040                              (q = ch.find(h, k, kc)) != null))
2041                             return q;
2042                     }
2043                     dir = tieBreakOrder(k, pk);
2044                 }
2045 
2046                 TreeNode<K,V> xp = p;
2047                 if ((p = (dir <= 0) ? p.left : p.right) == null) {
2048                     Node<K,V> xpn = xp.next;
2049                     TreeNode<K,V> x = map.newTreeNode(h, k, v, xpn);
2050                     if (dir <= 0)
2051                         xp.left = x;
2052                     else
2053                         xp.right = x;
2054                     xp.next = x;
2055                     x.parent = x.prev = xp;
2056                     if (xpn != null)
2057                         ((TreeNode<K,V>)xpn).prev = x;
2058                     moveRootToFront(tab, balanceInsertion(root, x));
2059                     return null;
2060                 }
2061             }
2062         }
2063 
2064         /**
2065          * Removes the given node, that must be present before this call.
2066          * This is messier than typical red-black deletion code because we
2067          * cannot swap the contents of an interior node with a leaf
2068          * successor that is pinned by "next" pointers that are accessible
2069          * independently during traversal. So instead we swap the tree
2070          * linkages. If the current tree appears to have too few nodes,
2071          * the bin is converted back to a plain bin. (The test triggers
2072          * somewhere between 2 and 6 nodes, depending on tree structure).
2073          */
2074         final void removeTreeNode(HashMap<K,V> map, Node<K,V>[] tab,
2075                                   boolean movable) {
2076             int n;
2077             if (tab == null || (n = tab.length) == 0)
2078                 return;
2079             int index = (n - 1) & hash;
2080             TreeNode<K,V> first = (TreeNode<K,V>)tab[index], root = first, rl;
2081             TreeNode<K,V> succ = (TreeNode<K,V>)next, pred = prev;
2082             if (pred == null)
2083                 tab[index] = first = succ;
2084             else
2085                 pred.next = succ;
2086             if (succ != null)
2087                 succ.prev = pred;
2088             if (first == null)
2089                 return;
2090             if (root.parent != null)
2091                 root = root.root();
2092             if (root == null
2093                 || (movable
2094                     && (root.right == null
2095                         || (rl = root.left) == null
2096                         || rl.left == null))) {
2097                 tab[index] = first.untreeify(map);  // too small
2098                 return;
2099             }
2100             TreeNode<K,V> p = this, pl = left, pr = right, replacement;
2101             if (pl != null && pr != null) {
2102                 TreeNode<K,V> s = pr, sl;
2103                 while ((sl = s.left) != null) // find successor
2104                     s = sl;
2105                 boolean c = s.red; s.red = p.red; p.red = c; // swap colors
2106                 TreeNode<K,V> sr = s.right;
2107                 TreeNode<K,V> pp = p.parent;
2108                 if (s == pr) { // p was s's direct parent
2109                     p.parent = s;
2110                     s.right = p;
2111                 }
2112                 else {
2113                     TreeNode<K,V> sp = s.parent;
2114                     if ((p.parent = sp) != null) {
2115                         if (s == sp.left)
2116                             sp.left = p;
2117                         else
2118                             sp.right = p;
2119                     }
2120                     if ((s.right = pr) != null)
2121                         pr.parent = s;
2122                 }
2123                 p.left = null;
2124                 if ((p.right = sr) != null)
2125                     sr.parent = p;
2126                 if ((s.left = pl) != null)
2127                     pl.parent = s;
2128                 if ((s.parent = pp) == null)
2129                     root = s;
2130                 else if (p == pp.left)
2131                     pp.left = s;
2132                 else
2133                     pp.right = s;
2134                 if (sr != null)
2135                     replacement = sr;
2136                 else
2137                     replacement = p;
2138             }
2139             else if (pl != null)
2140                 replacement = pl;
2141             else if (pr != null)
2142                 replacement = pr;
2143             else
2144                 replacement = p;
2145             if (replacement != p) {
2146                 TreeNode<K,V> pp = replacement.parent = p.parent;
2147                 if (pp == null)
2148                     (root = replacement).red = false;
2149                 else if (p == pp.left)
2150                     pp.left = replacement;
2151                 else
2152                     pp.right = replacement;
2153                 p.left = p.right = p.parent = null;
2154             }
2155 
2156             TreeNode<K,V> r = p.red ? root : balanceDeletion(root, replacement);
2157 
2158             if (replacement == p) {  // detach
2159                 TreeNode<K,V> pp = p.parent;
2160                 p.parent = null;
2161                 if (pp != null) {
2162                     if (p == pp.left)
2163                         pp.left = null;
2164                     else if (p == pp.right)
2165                         pp.right = null;
2166                 }
2167             }
2168             if (movable)
2169                 moveRootToFront(tab, r);
2170         }
2171 
2172         /**
2173          * Splits nodes in a tree bin into lower and upper tree bins,
2174          * or untreeifies if now too small. Called only from resize;
2175          * see above discussion about split bits and indices.
2176          *
2177          * @param map the map
2178          * @param tab the table for recording bin heads
2179          * @param index the index of the table being split
2180          * @param bit the bit of hash to split on
2181          */
2182         final void split(HashMap<K,V> map, Node<K,V>[] tab, int index, int bit) {
2183             TreeNode<K,V> b = this;
2184             // Relink into lo and hi lists, preserving order
2185             TreeNode<K,V> loHead = null, loTail = null;
2186             TreeNode<K,V> hiHead = null, hiTail = null;
2187             int lc = 0, hc = 0;
2188             for (TreeNode<K,V> e = b, next; e != null; e = next) {
2189                 next = (TreeNode<K,V>)e.next;
2190                 e.next = null;
2191                 if ((e.hash & bit) == 0) {
2192                     if ((e.prev = loTail) == null)
2193                         loHead = e;
2194                     else
2195                         loTail.next = e;
2196                     loTail = e;
2197                     ++lc;
2198                 }
2199                 else {
2200                     if ((e.prev = hiTail) == null)
2201                         hiHead = e;
2202                     else
2203                         hiTail.next = e;
2204                     hiTail = e;
2205                     ++hc;
2206                 }
2207             }
2208 
2209             if (loHead != null) {
2210                 if (lc <= UNTREEIFY_THRESHOLD)
2211                     tab[index] = loHead.untreeify(map);
2212                 else {
2213                     tab[index] = loHead;
2214                     if (hiHead != null) // (else is already treeified)
2215                         loHead.treeify(tab);
2216                 }
2217             }
2218             if (hiHead != null) {
2219                 if (hc <= UNTREEIFY_THRESHOLD)
2220                     tab[index + bit] = hiHead.untreeify(map);
2221                 else {
2222                     tab[index + bit] = hiHead;
2223                     if (loHead != null)
2224                         hiHead.treeify(tab);
2225                 }
2226             }
2227         }
2228 
2229         /* ------------------------------------------------------------ */
2230         // Red-black tree methods, all adapted from CLR
2231 
2232         static <K,V> TreeNode<K,V> rotateLeft(TreeNode<K,V> root,
2233                                               TreeNode<K,V> p) {
2234             TreeNode<K,V> r, pp, rl;
2235             if (p != null && (r = p.right) != null) {
2236                 if ((rl = p.right = r.left) != null)
2237                     rl.parent = p;
2238                 if ((pp = r.parent = p.parent) == null)
2239                     (root = r).red = false;
2240                 else if (pp.left == p)
2241                     pp.left = r;
2242                 else
2243                     pp.right = r;
2244                 r.left = p;
2245                 p.parent = r;
2246             }
2247             return root;
2248         }
2249 
2250         static <K,V> TreeNode<K,V> rotateRight(TreeNode<K,V> root,
2251                                                TreeNode<K,V> p) {
2252             TreeNode<K,V> l, pp, lr;
2253             if (p != null && (l = p.left) != null) {
2254                 if ((lr = p.left = l.right) != null)
2255                     lr.parent = p;
2256                 if ((pp = l.parent = p.parent) == null)
2257                     (root = l).red = false;
2258                 else if (pp.right == p)
2259                     pp.right = l;
2260                 else
2261                     pp.left = l;
2262                 l.right = p;
2263                 p.parent = l;
2264             }
2265             return root;
2266         }
2267 
2268         static <K,V> TreeNode<K,V> balanceInsertion(TreeNode<K,V> root,
2269                                                     TreeNode<K,V> x) {
2270             x.red = true;
2271             for (TreeNode<K,V> xp, xpp, xppl, xppr;;) {
2272                 if ((xp = x.parent) == null) {
2273                     x.red = false;
2274                     return x;
2275                 }
2276                 else if (!xp.red || (xpp = xp.parent) == null)
2277                     return root;
2278                 if (xp == (xppl = xpp.left)) {
2279                     if ((xppr = xpp.right) != null && xppr.red) {
2280                         xppr.red = false;
2281                         xp.red = false;
2282                         xpp.red = true;
2283                         x = xpp;
2284                     }
2285                     else {
2286                         if (x == xp.right) {
2287                             root = rotateLeft(root, x = xp);
2288                             xpp = (xp = x.parent) == null ? null : xp.parent;
2289                         }
2290                         if (xp != null) {
2291                             xp.red = false;
2292                             if (xpp != null) {
2293                                 xpp.red = true;
2294                                 root = rotateRight(root, xpp);
2295                             }
2296                         }
2297                     }
2298                 }
2299                 else {
2300                     if (xppl != null && xppl.red) {
2301                         xppl.red = false;
2302                         xp.red = false;
2303                         xpp.red = true;
2304                         x = xpp;
2305                     }
2306                     else {
2307                         if (x == xp.left) {
2308                             root = rotateRight(root, x = xp);
2309                             xpp = (xp = x.parent) == null ? null : xp.parent;
2310                         }
2311                         if (xp != null) {
2312                             xp.red = false;
2313                             if (xpp != null) {
2314                                 xpp.red = true;
2315                                 root = rotateLeft(root, xpp);
2316                             }
2317                         }
2318                     }
2319                 }
2320             }
2321         }
2322 
2323         static <K,V> TreeNode<K,V> balanceDeletion(TreeNode<K,V> root,
2324                                                    TreeNode<K,V> x) {
2325             for (TreeNode<K,V> xp, xpl, xpr;;) {
2326                 if (x == null || x == root)
2327                     return root;
2328                 else if ((xp = x.parent) == null) {
2329                     x.red = false;
2330                     return x;
2331                 }
2332                 else if (x.red) {
2333                     x.red = false;
2334                     return root;
2335                 }
2336                 else if ((xpl = xp.left) == x) {
2337                     if ((xpr = xp.right) != null && xpr.red) {
2338                         xpr.red = false;
2339                         xp.red = true;
2340                         root = rotateLeft(root, xp);
2341                         xpr = (xp = x.parent) == null ? null : xp.right;
2342                     }
2343                     if (xpr == null)
2344                         x = xp;
2345                     else {
2346                         TreeNode<K,V> sl = xpr.left, sr = xpr.right;
2347                         if ((sr == null || !sr.red) &&
2348                             (sl == null || !sl.red)) {
2349                             xpr.red = true;
2350                             x = xp;
2351                         }
2352                         else {
2353                             if (sr == null || !sr.red) {
2354                                 if (sl != null)
2355                                     sl.red = false;
2356                                 xpr.red = true;
2357                                 root = rotateRight(root, xpr);
2358                                 xpr = (xp = x.parent) == null ?
2359                                     null : xp.right;
2360                             }
2361                             if (xpr != null) {
2362                                 xpr.red = (xp == null) ? false : xp.red;
2363                                 if ((sr = xpr.right) != null)
2364                                     sr.red = false;
2365                             }
2366                             if (xp != null) {
2367                                 xp.red = false;
2368                                 root = rotateLeft(root, xp);
2369                             }
2370                             x = root;
2371                         }
2372                     }
2373                 }
2374                 else { // symmetric
2375                     if (xpl != null && xpl.red) {
2376                         xpl.red = false;
2377                         xp.red = true;
2378                         root = rotateRight(root, xp);
2379                         xpl = (xp = x.parent) == null ? null : xp.left;
2380                     }
2381                     if (xpl == null)
2382                         x = xp;
2383                     else {
2384                         TreeNode<K,V> sl = xpl.left, sr = xpl.right;
2385                         if ((sl == null || !sl.red) &&
2386                             (sr == null || !sr.red)) {
2387                             xpl.red = true;
2388                             x = xp;
2389                         }
2390                         else {
2391                             if (sl == null || !sl.red) {
2392                                 if (sr != null)
2393                                     sr.red = false;
2394                                 xpl.red = true;
2395                                 root = rotateLeft(root, xpl);
2396                                 xpl = (xp = x.parent) == null ?
2397                                     null : xp.left;
2398                             }
2399                             if (xpl != null) {
2400                                 xpl.red = (xp == null) ? false : xp.red;
2401                                 if ((sl = xpl.left) != null)
2402                                     sl.red = false;
2403                             }
2404                             if (xp != null) {
2405                                 xp.red = false;
2406                                 root = rotateRight(root, xp);
2407                             }
2408                             x = root;
2409                         }
2410                     }
2411                 }
2412             }
2413         }
2414 
2415         /**
2416          * Recursive invariant check
2417          */
2418         static <K,V> boolean checkInvariants(TreeNode<K,V> t) {
2419             TreeNode<K,V> tp = t.parent, tl = t.left, tr = t.right,
2420                 tb = t.prev, tn = (TreeNode<K,V>)t.next;
2421             if (tb != null && tb.next != t)
2422                 return false;
2423             if (tn != null && tn.prev != t)
2424                 return false;
2425             if (tp != null && t != tp.left && t != tp.right)
2426                 return false;
2427             if (tl != null && (tl.parent != t || tl.hash > t.hash))
2428                 return false;
2429             if (tr != null && (tr.parent != t || tr.hash < t.hash))
2430                 return false;
2431             if (t.red && tl != null && tl.red && tr != null && tr.red)
2432                 return false;
2433             if (tl != null && !checkInvariants(tl))
2434                 return false;
2435             if (tr != null && !checkInvariants(tr))
2436                 return false;
2437             return true;
2438         }
2439     }
2440 
2441 }
--- EOF ---