src/share/classes/java/util/HashMap.java

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rev 6816 : 80111200: (coll) Optimize empty HashMap and ArrayList
Reviewed-by: mduigou
Contributed-by: Sergey Linetskiy <sergey.linetskiy@oracle.com>, John Rose <john.r.rose@oracle.com>, Mike Duigou <mike.duigou@oracle.com>
   1 /*
   2  * Copyright (c) 1997, 2012, 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


 127 {
 128 
 129     /**
 130      * The default initial capacity - MUST be a power of two.
 131      */
 132     static final int DEFAULT_INITIAL_CAPACITY = 16;
 133 
 134     /**
 135      * The maximum capacity, used if a higher value is implicitly specified
 136      * by either of the constructors with arguments.
 137      * MUST be a power of two <= 1<<30.
 138      */
 139     static final int MAXIMUM_CAPACITY = 1 << 30;
 140 
 141     /**
 142      * The load factor used when none specified in constructor.
 143      */
 144     static final float DEFAULT_LOAD_FACTOR = 0.75f;
 145 
 146     /**





 147      * The table, resized as necessary. Length MUST Always be a power of two.
 148      */
 149     transient Entry<?,?>[] table;
 150 
 151     /**
 152      * The number of key-value mappings contained in this map.
 153      */
 154     transient int size;
 155 
 156     /**
 157      * The next size value at which to resize (capacity * load factor).
 158      * @serial
 159      */
 160     int threshold;
 161 
 162     /**
 163      * The load factor for the hash table.
 164      *
 165      * @serial
 166      */
 167     final float loadFactor;
 168 
 169     /**


 206 
 207     /**
 208      * Constructs an empty <tt>HashMap</tt> with the specified initial
 209      * capacity and load factor.
 210      *
 211      * @param  initialCapacity the initial capacity
 212      * @param  loadFactor      the load factor
 213      * @throws IllegalArgumentException if the initial capacity is negative
 214      *         or the load factor is nonpositive
 215      */
 216     public HashMap(int initialCapacity, float loadFactor) {
 217         if (initialCapacity < 0)
 218             throw new IllegalArgumentException("Illegal initial capacity: " +
 219                                                initialCapacity);
 220         if (initialCapacity > MAXIMUM_CAPACITY)
 221             initialCapacity = MAXIMUM_CAPACITY;
 222         if (loadFactor <= 0 || Float.isNaN(loadFactor))
 223             throw new IllegalArgumentException("Illegal load factor: " +
 224                                                loadFactor);
 225 
 226         // Find a power of 2 >= initialCapacity
 227         int capacity = 1;
 228         while (capacity < initialCapacity)
 229             capacity <<= 1;
 230 
 231         this.loadFactor = loadFactor;
 232         threshold = (int)Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
 233         table = new Entry<?,?>[capacity];
 234         init();
 235     }
 236 
 237     /**
 238      * Constructs an empty <tt>HashMap</tt> with the specified initial
 239      * capacity and the default load factor (0.75).
 240      *
 241      * @param  initialCapacity the initial capacity.
 242      * @throws IllegalArgumentException if the initial capacity is negative.
 243      */
 244     public HashMap(int initialCapacity) {
 245         this(initialCapacity, DEFAULT_LOAD_FACTOR);
 246     }
 247 
 248     /**
 249      * Constructs an empty <tt>HashMap</tt> with the default initial capacity
 250      * (16) and the default load factor (0.75).
 251      */
 252     public HashMap() {
 253         this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
 254     }
 255 
 256     /**
 257      * Constructs a new <tt>HashMap</tt> with the same mappings as the
 258      * specified <tt>Map</tt>.  The <tt>HashMap</tt> is created with
 259      * default load factor (0.75) and an initial capacity sufficient to
 260      * hold the mappings in the specified <tt>Map</tt>.
 261      *
 262      * @param   m the map whose mappings are to be placed in this map
 263      * @throws  NullPointerException if the specified map is null
 264      */
 265     public HashMap(Map<? extends K, ? extends V> m) {
 266         this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
 267                       DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);


 268         putAllForCreate(m);
 269     }
 270 



















 271     // internal utilities
 272 
 273     /**
 274      * Initialization hook for subclasses. This method is called
 275      * in all constructors and pseudo-constructors (clone, readObject)
 276      * after HashMap has been initialized but before any entries have
 277      * been inserted.  (In the absence of this method, readObject would
 278      * require explicit knowledge of subclasses.)
 279      */
 280     void init() {
 281     }
 282 
 283     /**
 284      * Retrieve object hash code and applies a supplemental hash function to the
 285      * result hash, which defends against poor quality hash functions.  This is
 286      * critical because HashMap uses power-of-two length hash tables, that
 287      * otherwise encounter collisions for hashCodes that do not differ
 288      * in lower bits.
 289      */
 290     final int hash(Object k) {
 291         if (k instanceof String) {
 292             return ((String) k).hash32();
 293         }
 294 
 295         int  h = hashSeed ^ k.hashCode();
 296 
 297         // This function ensures that hashCodes that differ only by
 298         // constant multiples at each bit position have a bounded
 299         // number of collisions (approximately 8 at default load factor).
 300         h ^= (h >>> 20) ^ (h >>> 12);
 301         return h ^ (h >>> 7) ^ (h >>> 4);
 302     }
 303 
 304     /**
 305      * Returns index for hash code h.
 306      */
 307     static int indexFor(int h, int length) {

 308         return h & (length-1);
 309     }
 310 
 311     /**
 312      * Returns the number of key-value mappings in this map.
 313      *
 314      * @return the number of key-value mappings in this map
 315      */
 316     public int size() {
 317         return size;
 318     }
 319 
 320     /**
 321      * Returns <tt>true</tt> if this map contains no key-value mappings.
 322      *
 323      * @return <tt>true</tt> if this map contains no key-value mappings
 324      */
 325     public boolean isEmpty() {
 326         return size == 0;
 327     }


 352 
 353     /**
 354      * Returns <tt>true</tt> if this map contains a mapping for the
 355      * specified key.
 356      *
 357      * @param   key   The key whose presence in this map is to be tested
 358      * @return <tt>true</tt> if this map contains a mapping for the specified
 359      * key.
 360      */
 361     public boolean containsKey(Object key) {
 362         return getEntry(key) != null;
 363     }
 364 
 365     /**
 366      * Returns the entry associated with the specified key in the
 367      * HashMap.  Returns null if the HashMap contains no mapping
 368      * for the key.
 369      */
 370     @SuppressWarnings("unchecked")
 371     final Entry<K,V> getEntry(Object key) {




 372         int hash = (key == null) ? 0 : hash(key);
 373         for (Entry<?,?> e = table[indexFor(hash, table.length)];
 374              e != null;
 375              e = e.next) {
 376             Object k;
 377             if (e.hash == hash &&
 378                 ((k = e.key) == key || (key != null && key.equals(k))))
 379                 return (Entry<K,V>)e;
 380         }
 381         return null;
 382     }
 383 
 384 
 385     /**
 386      * Associates the specified value with the specified key in this map.
 387      * If the map previously contained a mapping for the key, the old
 388      * value is replaced.
 389      *
 390      * @param key key with which the specified value is to be associated
 391      * @param value value to be associated with the specified key
 392      * @return the previous value associated with <tt>key</tt>, or
 393      *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
 394      *         (A <tt>null</tt> return can also indicate that the map
 395      *         previously associated <tt>null</tt> with <tt>key</tt>.)
 396      */
 397     public V put(K key, V value) {



 398         if (key == null)
 399             return putForNullKey(value);
 400         int hash = hash(key);
 401         int i = indexFor(hash, table.length);
 402         @SuppressWarnings("unchecked")
 403         Entry<K,V> e = (Entry<K,V>)table[i];
 404         for(; e != null; e = e.next) {
 405             Object k;
 406             if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
 407                 V oldValue = e.value;
 408                 e.value = value;
 409                 e.recordAccess(this);
 410                 return oldValue;
 411             }
 412         }
 413 
 414         modCount++;
 415         addEntry(hash, key, value, i);
 416         return null;
 417     }


 512                 newTable[i] = e;
 513                 e = next;
 514             }
 515         }
 516         Arrays.fill(table, null);
 517     }
 518 
 519     /**
 520      * Copies all of the mappings from the specified map to this map.
 521      * These mappings will replace any mappings that this map had for
 522      * any of the keys currently in the specified map.
 523      *
 524      * @param m mappings to be stored in this map
 525      * @throws NullPointerException if the specified map is null
 526      */
 527     public void putAll(Map<? extends K, ? extends V> m) {
 528         int numKeysToBeAdded = m.size();
 529         if (numKeysToBeAdded == 0)
 530             return;
 531 




 532         /*
 533          * Expand the map if the map if the number of mappings to be added
 534          * is greater than or equal to threshold.  This is conservative; the
 535          * obvious condition is (m.size() + size) >= threshold, but this
 536          * condition could result in a map with twice the appropriate capacity,
 537          * if the keys to be added overlap with the keys already in this map.
 538          * By using the conservative calculation, we subject ourself
 539          * to at most one extra resize.
 540          */
 541         if (numKeysToBeAdded > threshold) {
 542             int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
 543             if (targetCapacity > MAXIMUM_CAPACITY)
 544                 targetCapacity = MAXIMUM_CAPACITY;
 545             int newCapacity = table.length;
 546             while (newCapacity < targetCapacity)
 547                 newCapacity <<= 1;
 548             if (newCapacity > table.length)
 549                 resize(newCapacity);
 550         }
 551 


 556     /**
 557      * Removes the mapping for the specified key from this map if present.
 558      *
 559      * @param  key key whose mapping is to be removed from the map
 560      * @return the previous value associated with <tt>key</tt>, or
 561      *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
 562      *         (A <tt>null</tt> return can also indicate that the map
 563      *         previously associated <tt>null</tt> with <tt>key</tt>.)
 564      */
 565     public V remove(Object key) {
 566         Entry<K,V> e = removeEntryForKey(key);
 567         return (e == null ? null : e.value);
 568     }
 569 
 570     /**
 571      * Removes and returns the entry associated with the specified key
 572      * in the HashMap.  Returns null if the HashMap contains no mapping
 573      * for this key.
 574      */
 575     final Entry<K,V> removeEntryForKey(Object key) {



 576         int hash = (key == null) ? 0 : hash(key);
 577         int i = indexFor(hash, table.length);
 578         @SuppressWarnings("unchecked")
 579             Entry<K,V> prev = (Entry<K,V>)table[i];
 580         Entry<K,V> e = prev;
 581 
 582         while (e != null) {
 583             Entry<K,V> next = e.next;
 584             Object k;
 585             if (e.hash == hash &&
 586                 ((k = e.key) == key || (key != null && key.equals(k)))) {
 587                 modCount++;
 588                 size--;
 589                 if (prev == e)
 590                     table[i] = next;
 591                 else
 592                     prev.next = next;
 593                 e.recordRemoval(this);
 594                 return e;
 595             }
 596             prev = e;
 597             e = next;
 598         }
 599 
 600         return e;
 601     }
 602 
 603     /**
 604      * Special version of remove for EntrySet using {@code Map.Entry.equals()}
 605      * for matching.
 606      */
 607     final Entry<K,V> removeMapping(Object o) {
 608         if (!(o instanceof Map.Entry))
 609             return null;
 610 
 611         Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
 612         Object key = entry.getKey();
 613         int hash = (key == null) ? 0 : hash(key);
 614         int i = indexFor(hash, table.length);
 615         @SuppressWarnings("unchecked")
 616             Entry<K,V> prev = (Entry<K,V>)table[i];
 617         Entry<K,V> e = prev;
 618 
 619         while (e != null) {
 620             Entry<K,V> next = e.next;
 621             if (e.hash == hash && e.equals(entry)) {
 622                 modCount++;
 623                 size--;
 624                 if (prev == e)
 625                     table[i] = next;
 626                 else
 627                     prev.next = next;
 628                 e.recordRemoval(this);
 629                 return e;
 630             }
 631             prev = e;
 632             e = next;
 633         }
 634 
 635         return e;
 636     }
 637 
 638     /**
 639      * Removes all of the mappings from this map.
 640      * The map will be empty after this call returns.
 641      */
 642     public void clear() {
 643         modCount++;
 644         Entry<?,?>[] tab = table;
 645         for (int i = 0; i < tab.length; i++)
 646             tab[i] = null;
 647         size = 0;
 648     }
 649 
 650     /**
 651      * Returns <tt>true</tt> if this map maps one or more keys to the
 652      * specified value.
 653      *
 654      * @param value value whose presence in this map is to be tested
 655      * @return <tt>true</tt> if this map maps one or more keys to the
 656      *         specified value
 657      */
 658     public boolean containsValue(Object value) {




 659         if (value == null)
 660             return containsNullValue();
 661 
 662         Entry<?,?>[] tab = table;
 663         for (int i = 0; i < tab.length ; i++)
 664             for (Entry<?,?> e = tab[i] ; e != null ; e = e.next)
 665                 if (value.equals(e.value))
 666                     return true;
 667         return false;
 668     }
 669 
 670     /**
 671      * Special-case code for containsValue with null argument
 672      */
 673     private boolean containsNullValue() {
 674         Entry<?,?>[] tab = table;
 675         for (int i = 0; i < tab.length ; i++)
 676             for (Entry<?,?> e = tab[i] ; e != null ; e = e.next)
 677                 if (e.value == null)
 678                     return true;
 679         return false;
 680     }
 681 
 682     /**
 683      * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
 684      * values themselves are not cloned.
 685      *
 686      * @return a shallow copy of this map
 687      */
 688     @SuppressWarnings("unchecked")
 689     public Object clone() {
 690         HashMap<K,V> result = null;
 691         try {
 692             result = (HashMap<K,V>)super.clone();
 693         } catch (CloneNotSupportedException e) {
 694             // assert false;
 695         }
 696         result.table = new Entry<?,?>[table.length];


 697         result.entrySet = null;
 698         result.modCount = 0;
 699         result.size = 0;
 700         result.init();
 701         result.putAllForCreate(this);
 702 
 703         return result;
 704     }
 705 
 706     static class Entry<K,V> implements Map.Entry<K,V> {
 707         final K key;
 708         V value;
 709         Entry<K,V> next;
 710         final int hash;
 711 
 712         /**
 713          * Creates new entry.
 714          */
 715         Entry(int h, K k, V v, Entry<K,V> n) {
 716             value = v;


 732             value = newValue;
 733             return oldValue;
 734         }
 735 
 736         public final boolean equals(Object o) {
 737             if (!(o instanceof Map.Entry))
 738                 return false;
 739             Map.Entry<?,?> e = (Map.Entry<?,?>)o;
 740             Object k1 = getKey();
 741             Object k2 = e.getKey();
 742             if (k1 == k2 || (k1 != null && k1.equals(k2))) {
 743                 Object v1 = getValue();
 744                 Object v2 = e.getValue();
 745                 if (v1 == v2 || (v1 != null && v1.equals(v2)))
 746                     return true;
 747             }
 748             return false;
 749         }
 750 
 751         public final int hashCode() {
 752             return (key==null   ? 0 : key.hashCode()) ^
 753                    (value==null ? 0 : value.hashCode());
 754         }
 755 
 756         public final String toString() {
 757             return getKey() + "=" + getValue();
 758         }
 759 
 760         /**
 761          * This method is invoked whenever the value in an entry is
 762          * overwritten by an invocation of put(k,v) for a key k that's already
 763          * in the HashMap.
 764          */
 765         void recordAccess(HashMap<K,V> m) {
 766         }
 767 
 768         /**
 769          * This method is invoked whenever the entry is
 770          * removed from the table.
 771          */
 772         void recordRemoval(HashMap<K,V> m) {
 773         }


 991             Map.Entry<?,?> e = (Map.Entry<?,?>) o;
 992             Entry<K,V> candidate = getEntry(e.getKey());
 993             return candidate != null && candidate.equals(e);
 994         }
 995         public boolean remove(Object o) {
 996             return removeMapping(o) != null;
 997         }
 998         public int size() {
 999             return size;
1000         }
1001         public void clear() {
1002             HashMap.this.clear();
1003         }
1004     }
1005 
1006     /**
1007      * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
1008      * serialize it).
1009      *
1010      * @serialData The <i>capacity</i> of the HashMap (the length of the
1011      *             bucket array) is emitted (int), followed by the
1012      *             <i>size</i> (an int, the number of key-value
1013      *             mappings), followed by the key (Object) and value (Object)
1014      *             for each key-value mapping.  The key-value mappings are
1015      *             emitted in no particular order.
1016      */
1017     private void writeObject(java.io.ObjectOutputStream s)
1018         throws IOException
1019     {
1020         Iterator<Map.Entry<K,V>> i =
1021             (size > 0) ? entrySet0().iterator() : null;
1022 
1023         // Write out the threshold, loadfactor, and any hidden stuff
1024         s.defaultWriteObject();
1025 
1026         // Write out number of buckets



1027         s.writeInt(table.length);

1028 
1029         // Write out size (number of Mappings)
1030         s.writeInt(size);
1031 
1032         // Write out keys and values (alternating)
1033         if (size > 0) {
1034             for(Map.Entry<K,V> e : entrySet0()) {
1035                 s.writeObject(e.getKey());
1036                 s.writeObject(e.getValue());
1037             }
1038         }
1039     }
1040 
1041     private static final long serialVersionUID = 362498820763181265L;
1042 
1043     /**
1044      * Reconstitute the {@code HashMap} instance from a stream (i.e.,
1045      * deserialize it).
1046      */
1047     private void readObject(java.io.ObjectInputStream s)
1048          throws IOException, ClassNotFoundException
1049     {
1050         // Read in the threshold (ignored), loadfactor, and any hidden stuff
1051         s.defaultReadObject();
1052         if (loadFactor <= 0 || Float.isNaN(loadFactor))
1053             throw new InvalidObjectException("Illegal load factor: " +
1054                                                loadFactor);

1055 
1056         // set hashMask
1057         Holder.UNSAFE.putIntVolatile(this, Holder.HASHSEED_OFFSET,
1058                 sun.misc.Hashing.randomHashSeed(this));
1059 
1060         // Read in number of buckets and allocate the bucket array;
1061         s.readInt(); // ignored








1062 
1063         // Read number of mappings
1064         int mappings = s.readInt();
1065         if (mappings < 0)
1066             throw new InvalidObjectException("Illegal mappings count: " +
1067                                                mappings);
1068 
1069         int initialCapacity = (int) Math.min(

1070                 // capacity chosen by number of mappings
1071                 // and desired load (if >= 0.25)
1072                 mappings * Math.min(1 / loadFactor, 4.0f),
1073                 // we have limits...
1074                 HashMap.MAXIMUM_CAPACITY);
1075         int capacity = 1;
1076         // find smallest power of two which holds all mappings
1077         while (capacity < initialCapacity) {
1078             capacity <<= 1;



1079         }
1080 
1081         table = new Entry<?,?>[capacity];
1082         threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
1083         init();  // Give subclass a chance to do its thing.
1084 
1085 
1086         // Read the keys and values, and put the mappings in the HashMap
1087         for (int i=0; i<mappings; i++) {
1088             @SuppressWarnings("unchecked")
1089                 K key = (K) s.readObject();
1090             @SuppressWarnings("unchecked")
1091                 V value = (V) s.readObject();
1092             putForCreate(key, value);
1093         }
1094     }
1095 
1096     // These methods are used when serializing HashSets
1097     int   capacity()     { return table.length; }
1098     float loadFactor()   { return loadFactor;   }
1099 }
   1 /*
   2  * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any


 127 {
 128 
 129     /**
 130      * The default initial capacity - MUST be a power of two.
 131      */
 132     static final int DEFAULT_INITIAL_CAPACITY = 16;
 133 
 134     /**
 135      * The maximum capacity, used if a higher value is implicitly specified
 136      * by either of the constructors with arguments.
 137      * MUST be a power of two <= 1<<30.
 138      */
 139     static final int MAXIMUM_CAPACITY = 1 << 30;
 140 
 141     /**
 142      * The load factor used when none specified in constructor.
 143      */
 144     static final float DEFAULT_LOAD_FACTOR = 0.75f;
 145 
 146     /**
 147      * An empty table instance to share when the table is not inflated.
 148      */
 149     static final Entry<?,?>[] EMPTY_TABLE = {};
 150 
 151     /**
 152      * The table, resized as necessary. Length MUST Always be a power of two.
 153      */
 154     transient Entry<?,?>[] table = EMPTY_TABLE;
 155 
 156     /**
 157      * The number of key-value mappings contained in this map.
 158      */
 159     transient int size;
 160 
 161     /**
 162      * The next size value at which to resize (capacity * load factor).
 163      * @serial
 164      */
 165     int threshold;
 166 
 167     /**
 168      * The load factor for the hash table.
 169      *
 170      * @serial
 171      */
 172     final float loadFactor;
 173 
 174     /**


 211 
 212     /**
 213      * Constructs an empty <tt>HashMap</tt> with the specified initial
 214      * capacity and load factor.
 215      *
 216      * @param  initialCapacity the initial capacity
 217      * @param  loadFactor      the load factor
 218      * @throws IllegalArgumentException if the initial capacity is negative
 219      *         or the load factor is nonpositive
 220      */
 221     public HashMap(int initialCapacity, float loadFactor) {
 222         if (initialCapacity < 0)
 223             throw new IllegalArgumentException("Illegal initial capacity: " +
 224                                                initialCapacity);
 225         if (initialCapacity > MAXIMUM_CAPACITY)
 226             initialCapacity = MAXIMUM_CAPACITY;
 227         if (loadFactor <= 0 || Float.isNaN(loadFactor))
 228             throw new IllegalArgumentException("Illegal load factor: " +
 229                                                loadFactor);
 230 





 231         this.loadFactor = loadFactor;
 232         threshold = initialCapacity;

 233         init();
 234     }
 235 
 236     /**
 237      * Constructs an empty <tt>HashMap</tt> with the specified initial
 238      * capacity and the default load factor (0.75).
 239      *
 240      * @param  initialCapacity the initial capacity.
 241      * @throws IllegalArgumentException if the initial capacity is negative.
 242      */
 243     public HashMap(int initialCapacity) {
 244         this(initialCapacity, DEFAULT_LOAD_FACTOR);
 245     }
 246 
 247     /**
 248      * Constructs an empty <tt>HashMap</tt> with the default initial capacity
 249      * (16) and the default load factor (0.75).
 250      */
 251     public HashMap() {
 252         this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
 253     }
 254 
 255     /**
 256      * Constructs a new <tt>HashMap</tt> with the same mappings as the
 257      * specified <tt>Map</tt>.  The <tt>HashMap</tt> is created with
 258      * default load factor (0.75) and an initial capacity sufficient to
 259      * hold the mappings in the specified <tt>Map</tt>.
 260      *
 261      * @param   m the map whose mappings are to be placed in this map
 262      * @throws  NullPointerException if the specified map is null
 263      */
 264     public HashMap(Map<? extends K, ? extends V> m) {
 265         this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
 266                       DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
 267         inflateTable(threshold);
 268 
 269         putAllForCreate(m);
 270     }
 271 
 272     private static int roundUpToPowerOf2(int number) {
 273         int rounded = (rounded = Integer.highestOneBit(number)) != 0
 274             ? (Integer.bitCount(number) > 1) ? rounded << 1 : rounded
 275             : 1;
 276 
 277         return rounded;
 278     }
 279 
 280     /**
 281      * Inflate the table
 282      */
 283     private void inflateTable(int toSize) {
 284         // Find a power of 2 >= initialCapacity
 285         int capacity = roundUpToPowerOf2(toSize);
 286 
 287         threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
 288         table = new Entry[capacity];
 289     }
 290 
 291     // internal utilities
 292 
 293     /**
 294      * Initialization hook for subclasses. This method is called
 295      * in all constructors and pseudo-constructors (clone, readObject)
 296      * after HashMap has been initialized but before any entries have
 297      * been inserted.  (In the absence of this method, readObject would
 298      * require explicit knowledge of subclasses.)
 299      */
 300     void init() {
 301     }
 302 
 303     /**
 304      * Retrieve object hash code and applies a supplemental hash function to the
 305      * result hash, which defends against poor quality hash functions.  This is
 306      * critical because HashMap uses power-of-two length hash tables, that
 307      * otherwise encounter collisions for hashCodes that do not differ
 308      * in lower bits.
 309      */
 310     final int hash(Object k) {
 311         if (k instanceof String) {
 312             return ((String) k).hash32();
 313         }
 314 
 315         int  h = hashSeed ^ k.hashCode();
 316 
 317         // This function ensures that hashCodes that differ only by
 318         // constant multiples at each bit position have a bounded
 319         // number of collisions (approximately 8 at default load factor).
 320         h ^= (h >>> 20) ^ (h >>> 12);
 321         return h ^ (h >>> 7) ^ (h >>> 4);
 322     }
 323 
 324     /**
 325      * Returns index for hash code h.
 326      */
 327     static int indexFor(int h, int length) {
 328         // assert Integer.bitCount(length) == 1 : "length must be a non-zero power of 2";
 329         return h & (length-1);
 330     }
 331 
 332     /**
 333      * Returns the number of key-value mappings in this map.
 334      *
 335      * @return the number of key-value mappings in this map
 336      */
 337     public int size() {
 338         return size;
 339     }
 340 
 341     /**
 342      * Returns <tt>true</tt> if this map contains no key-value mappings.
 343      *
 344      * @return <tt>true</tt> if this map contains no key-value mappings
 345      */
 346     public boolean isEmpty() {
 347         return size == 0;
 348     }


 373 
 374     /**
 375      * Returns <tt>true</tt> if this map contains a mapping for the
 376      * specified key.
 377      *
 378      * @param   key   The key whose presence in this map is to be tested
 379      * @return <tt>true</tt> if this map contains a mapping for the specified
 380      * key.
 381      */
 382     public boolean containsKey(Object key) {
 383         return getEntry(key) != null;
 384     }
 385 
 386     /**
 387      * Returns the entry associated with the specified key in the
 388      * HashMap.  Returns null if the HashMap contains no mapping
 389      * for the key.
 390      */
 391     @SuppressWarnings("unchecked")
 392     final Entry<K,V> getEntry(Object key) {
 393         if (isEmpty()) {
 394             return null;
 395         }
 396 
 397         int hash = (key == null) ? 0 : hash(key);
 398         for (Entry<?,?> e = table[indexFor(hash, table.length)];
 399              e != null;
 400              e = e.next) {
 401             Object k;
 402             if (e.hash == hash &&
 403                 ((k = e.key) == key || (key != null && key.equals(k))))
 404                 return (Entry<K,V>)e;
 405         }
 406         return null;
 407     }
 408 

 409     /**
 410      * Associates the specified value with the specified key in this map.
 411      * If the map previously contained a mapping for the key, the old
 412      * value is replaced.
 413      *
 414      * @param key key with which the specified value is to be associated
 415      * @param value value to be associated with the specified key
 416      * @return the previous value associated with <tt>key</tt>, or
 417      *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
 418      *         (A <tt>null</tt> return can also indicate that the map
 419      *         previously associated <tt>null</tt> with <tt>key</tt>.)
 420      */
 421     public V put(K key, V value) {
 422         if (table == EMPTY_TABLE) {
 423             inflateTable(threshold);
 424         }
 425         if (key == null)
 426             return putForNullKey(value);
 427         int hash = hash(key);
 428         int i = indexFor(hash, table.length);
 429         @SuppressWarnings("unchecked")
 430         Entry<K,V> e = (Entry<K,V>)table[i];
 431         for(; e != null; e = e.next) {
 432             Object k;
 433             if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
 434                 V oldValue = e.value;
 435                 e.value = value;
 436                 e.recordAccess(this);
 437                 return oldValue;
 438             }
 439         }
 440 
 441         modCount++;
 442         addEntry(hash, key, value, i);
 443         return null;
 444     }


 539                 newTable[i] = e;
 540                 e = next;
 541             }
 542         }
 543         Arrays.fill(table, null);
 544     }
 545 
 546     /**
 547      * Copies all of the mappings from the specified map to this map.
 548      * These mappings will replace any mappings that this map had for
 549      * any of the keys currently in the specified map.
 550      *
 551      * @param m mappings to be stored in this map
 552      * @throws NullPointerException if the specified map is null
 553      */
 554     public void putAll(Map<? extends K, ? extends V> m) {
 555         int numKeysToBeAdded = m.size();
 556         if (numKeysToBeAdded == 0)
 557             return;
 558 
 559         if (table == EMPTY_TABLE) {
 560             inflateTable(Math.max((int) (numKeysToBeAdded * loadFactor), threshold));
 561         }
 562 
 563         /*
 564          * Expand the map if the map if the number of mappings to be added
 565          * is greater than or equal to threshold.  This is conservative; the
 566          * obvious condition is (m.size() + size) >= threshold, but this
 567          * condition could result in a map with twice the appropriate capacity,
 568          * if the keys to be added overlap with the keys already in this map.
 569          * By using the conservative calculation, we subject ourself
 570          * to at most one extra resize.
 571          */
 572         if (numKeysToBeAdded > threshold) {
 573             int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
 574             if (targetCapacity > MAXIMUM_CAPACITY)
 575                 targetCapacity = MAXIMUM_CAPACITY;
 576             int newCapacity = table.length;
 577             while (newCapacity < targetCapacity)
 578                 newCapacity <<= 1;
 579             if (newCapacity > table.length)
 580                 resize(newCapacity);
 581         }
 582 


 587     /**
 588      * Removes the mapping for the specified key from this map if present.
 589      *
 590      * @param  key key whose mapping is to be removed from the map
 591      * @return the previous value associated with <tt>key</tt>, or
 592      *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
 593      *         (A <tt>null</tt> return can also indicate that the map
 594      *         previously associated <tt>null</tt> with <tt>key</tt>.)
 595      */
 596     public V remove(Object key) {
 597         Entry<K,V> e = removeEntryForKey(key);
 598         return (e == null ? null : e.value);
 599     }
 600 
 601     /**
 602      * Removes and returns the entry associated with the specified key
 603      * in the HashMap.  Returns null if the HashMap contains no mapping
 604      * for this key.
 605      */
 606     final Entry<K,V> removeEntryForKey(Object key) {
 607         if (isEmpty()) {
 608             return null;
 609         }
 610         int hash = (key == null) ? 0 : hash(key);
 611         int i = indexFor(hash, table.length);
 612         @SuppressWarnings("unchecked")
 613             Entry<K,V> prev = (Entry<K,V>)table[i];
 614         Entry<K,V> e = prev;
 615 
 616         while (e != null) {
 617             Entry<K,V> next = e.next;
 618             Object k;
 619             if (e.hash == hash &&
 620                 ((k = e.key) == key || (key != null && key.equals(k)))) {
 621                 modCount++;
 622                 size--;
 623                 if (prev == e)
 624                     table[i] = next;
 625                 else
 626                     prev.next = next;
 627                 e.recordRemoval(this);
 628                 return e;
 629             }
 630             prev = e;
 631             e = next;
 632         }
 633 
 634         return e;
 635     }
 636 
 637     /**
 638      * Special version of remove for EntrySet using {@code Map.Entry.equals()}
 639      * for matching.
 640      */
 641     final Entry<K,V> removeMapping(Object o) {
 642         if (isEmpty() || !(o instanceof Map.Entry))
 643             return null;
 644 
 645         Map.Entry<?,?> entry = (Map.Entry<?,?>) o;
 646         Object key = entry.getKey();
 647         int hash = (key == null) ? 0 : hash(key);
 648         int i = indexFor(hash, table.length);
 649         @SuppressWarnings("unchecked")
 650             Entry<K,V> prev = (Entry<K,V>)table[i];
 651         Entry<K,V> e = prev;
 652 
 653         while (e != null) {
 654             Entry<K,V> next = e.next;
 655             if (e.hash == hash && e.equals(entry)) {
 656                 modCount++;
 657                 size--;
 658                 if (prev == e)
 659                     table[i] = next;
 660                 else
 661                     prev.next = next;
 662                 e.recordRemoval(this);
 663                 return e;
 664             }
 665             prev = e;
 666             e = next;
 667         }
 668 
 669         return e;
 670     }
 671 
 672     /**
 673      * Removes all of the mappings from this map.
 674      * The map will be empty after this call returns.
 675      */
 676     public void clear() {
 677         modCount++;
 678         Arrays.fill(table, null);


 679         size = 0;
 680     }
 681 
 682     /**
 683      * Returns <tt>true</tt> if this map maps one or more keys to the
 684      * specified value.
 685      *
 686      * @param value value whose presence in this map is to be tested
 687      * @return <tt>true</tt> if this map maps one or more keys to the
 688      *         specified value
 689      */
 690     public boolean containsValue(Object value) {
 691         if (isEmpty()) {
 692             return false;
 693         }
 694 
 695         if (value == null)
 696             return containsNullValue();
 697 
 698         Entry<?,?>[] tab = table;
 699         for (int i = 0; i < tab.length ; i++)
 700             for (Entry<?,?> e = tab[i] ; e != null ; e = e.next)
 701                 if (value.equals(e.value))
 702                     return true;
 703         return false;
 704     }
 705 
 706     /**
 707      * Special-case code for containsValue with null argument
 708      */
 709     private boolean containsNullValue() {
 710         Entry<?,?>[] tab = table;
 711         for (int i = 0; i < tab.length ; i++)
 712             for (Entry<?,?> e = tab[i] ; e != null ; e = e.next)
 713                 if (e.value == null)
 714                     return true;
 715         return false;
 716     }
 717 
 718     /**
 719      * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
 720      * values themselves are not cloned.
 721      *
 722      * @return a shallow copy of this map
 723      */
 724     @SuppressWarnings("unchecked")
 725     public Object clone() {
 726         HashMap<K,V> result = null;
 727         try {
 728             result = (HashMap<K,V>)super.clone();
 729         } catch (CloneNotSupportedException e) {
 730             // assert false;
 731         }
 732         result.table = (table == EMPTY_TABLE)
 733             ? EMPTY_TABLE
 734             : new Entry<?,?>[table.length];
 735         result.entrySet = null;
 736         result.modCount = 0;
 737         result.size = 0;
 738         result.init();
 739         result.putAllForCreate(this);
 740 
 741         return result;
 742     }
 743 
 744     static class Entry<K,V> implements Map.Entry<K,V> {
 745         final K key;
 746         V value;
 747         Entry<K,V> next;
 748         final int hash;
 749 
 750         /**
 751          * Creates new entry.
 752          */
 753         Entry(int h, K k, V v, Entry<K,V> n) {
 754             value = v;


 770             value = newValue;
 771             return oldValue;
 772         }
 773 
 774         public final boolean equals(Object o) {
 775             if (!(o instanceof Map.Entry))
 776                 return false;
 777             Map.Entry<?,?> e = (Map.Entry<?,?>)o;
 778             Object k1 = getKey();
 779             Object k2 = e.getKey();
 780             if (k1 == k2 || (k1 != null && k1.equals(k2))) {
 781                 Object v1 = getValue();
 782                 Object v2 = e.getValue();
 783                 if (v1 == v2 || (v1 != null && v1.equals(v2)))
 784                     return true;
 785             }
 786             return false;
 787         }
 788 
 789         public final int hashCode() {
 790             return Objects.hashCode(getKey()) ^ Objects.hashCode(getValue());

 791         }
 792 
 793         public final String toString() {
 794             return getKey() + "=" + getValue();
 795         }
 796 
 797         /**
 798          * This method is invoked whenever the value in an entry is
 799          * overwritten by an invocation of put(k,v) for a key k that's already
 800          * in the HashMap.
 801          */
 802         void recordAccess(HashMap<K,V> m) {
 803         }
 804 
 805         /**
 806          * This method is invoked whenever the entry is
 807          * removed from the table.
 808          */
 809         void recordRemoval(HashMap<K,V> m) {
 810         }


1028             Map.Entry<?,?> e = (Map.Entry<?,?>) o;
1029             Entry<K,V> candidate = getEntry(e.getKey());
1030             return candidate != null && candidate.equals(e);
1031         }
1032         public boolean remove(Object o) {
1033             return removeMapping(o) != null;
1034         }
1035         public int size() {
1036             return size;
1037         }
1038         public void clear() {
1039             HashMap.this.clear();
1040         }
1041     }
1042 
1043     /**
1044      * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
1045      * serialize it).
1046      *
1047      * @serialData The <i>capacity</i> of the HashMap (the length of the
1048      *             bucket array, a power of 2) is emitted (int), followed by the
1049      *             <i>size</i> (an int, the number of key-value
1050      *             mappings), followed by the key (Object) and value (Object)
1051      *             for each key-value mapping.  The key-value mappings are
1052      *             emitted in no particular order.
1053      */
1054     private void writeObject(java.io.ObjectOutputStream s)
1055         throws IOException
1056     {



1057         // Write out the threshold, loadfactor, and any hidden stuff
1058         s.defaultWriteObject();
1059 
1060         // Write out number of buckets
1061         if (table==EMPTY_TABLE) {
1062             s.writeInt(roundUpToPowerOf2(threshold));
1063         } else {
1064            s.writeInt(table.length);
1065         }
1066 
1067         // Write out size (number of Mappings)
1068         s.writeInt(size);
1069 
1070         // Write out keys and values (alternating)
1071         if (size > 0) {
1072             for(Map.Entry<K,V> e : entrySet0()) {
1073                 s.writeObject(e.getKey());
1074                 s.writeObject(e.getValue());
1075             }
1076         }
1077     }
1078 
1079     private static final long serialVersionUID = 362498820763181265L;
1080 
1081     /**
1082      * Reconstitute the {@code HashMap} instance from a stream (i.e.,
1083      * deserialize it).
1084      */
1085     private void readObject(java.io.ObjectInputStream s)
1086          throws IOException, ClassNotFoundException
1087     {
1088         // Read in the threshold (ignored), loadfactor, and any hidden stuff
1089         s.defaultReadObject();
1090         if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
1091             throw new InvalidObjectException("Illegal load factor: " +
1092                                                loadFactor);
1093         }
1094 
1095         // set hashMask
1096         Holder.UNSAFE.putIntVolatile(this, Holder.HASHSEED_OFFSET,
1097                 sun.misc.Hashing.randomHashSeed(this));
1098 
1099         // Read in number of buckets and allocate the bucket array;
1100         table = EMPTY_TABLE;
1101 
1102         int buckets = s.readInt();
1103 
1104         if ((buckets < 0) || // negative
1105             (buckets > HashMap.MAXIMUM_CAPACITY) || // too big
1106             (Integer.bitCount(buckets) > 1)) /* not power of 2 or zero */ {
1107             throw new InvalidObjectException("Illegal capacity: " + buckets);
1108         }
1109 
1110         // Read number of mappings
1111         int mappings = s.readInt();
1112         if (mappings < 0)
1113             throw new InvalidObjectException("Illegal mappings count: " +
1114                                                mappings);
1115 
1116         int mappingsCapacity = Math.max(
1117                 (int) Math.min(
1118                     // capacity chosen by number of mappings
1119                     // and desired load (if >= 0.25)
1120                     mappings * Math.min(1 / loadFactor, 4.0f),
1121                     // we have limits...
1122                     HashMap.MAXIMUM_CAPACITY),
1123                 // maybe they want extra buckets.
1124                 buckets);
1125 
1126         if (mappings > 0) {
1127             inflateTable(mappingsCapacity);
1128         } else {
1129             threshold = mappingsCapacity;
1130         }
1131 


1132         init();  // Give subclass a chance to do its thing.

1133 
1134         // Read the keys and values, and put the mappings in the HashMap
1135         for (int i=0; i<mappings; i++) {
1136             @SuppressWarnings("unchecked")
1137                 K key = (K) s.readObject();
1138             @SuppressWarnings("unchecked")
1139                 V value = (V) s.readObject();
1140             putForCreate(key, value);
1141         }
1142     }
1143 
1144     // These methods are used when serializing HashSets
1145     int   capacity()     { return table.length; }
1146     float loadFactor()   { return loadFactor;   }
1147 }