0001: /*
0002: * @(#)HashMap.java 1.45 06/10/10
0003: *
0004: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
0005: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
0006: *
0007: * This program is free software; you can redistribute it and/or
0008: * modify it under the terms of the GNU General Public License version
0009: * 2 only, as published by the Free Software Foundation.
0010: *
0011: * This program is distributed in the hope that it will be useful, but
0012: * WITHOUT ANY WARRANTY; without even the implied warranty of
0013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
0014: * General Public License version 2 for more details (a copy is
0015: * included at /legal/license.txt).
0016: *
0017: * You should have received a copy of the GNU General Public License
0018: * version 2 along with this work; if not, write to the Free Software
0019: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
0020: * 02110-1301 USA
0021: *
0022: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
0023: * Clara, CA 95054 or visit www.sun.com if you need additional
0024: * information or have any questions.
0025: *
0026: */
0027:
0028: package java.util;
0029:
0030: import java.io.*;
0031:
0032: /**
0033: * Hash table based implementation of the <tt>Map</tt> interface. This
0034: * implementation provides all of the optional map operations, and permits
0035: * <tt>null</tt> values and the <tt>null</tt> key. (The <tt>HashMap</tt>
0036: * class is roughly equivalent to <tt>Hashtable</tt>, except that it is
0037: * unsynchronized and permits nulls.) This class makes no guarantees as to
0038: * the order of the map; in particular, it does not guarantee that the order
0039: * will remain constant over time.
0040: *
0041: * <p>This implementation provides constant-time performance for the basic
0042: * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
0043: * disperses the elements properly among the buckets. Iteration over
0044: * collection views requires time proportional to the "capacity" of the
0045: * <tt>HashMap</tt> instance (the number of buckets) plus its size (the number
0046: * of key-value mappings). Thus, it's very important not to set the initial
0047: * capacity too high (or the load factor too low) if iteration performance is
0048: * important.
0049: *
0050: * <p>An instance of <tt>HashMap</tt> has two parameters that affect its
0051: * performance: <i>initial capacity</i> and <i>load factor</i>. The
0052: * <i>capacity</i> is the number of buckets in the hash table, and the initial
0053: * capacity is simply the capacity at the time the hash table is created. The
0054: * <i>load factor</i> is a measure of how full the hash table is allowed to
0055: * get before its capacity is automatically increased. When the number of
0056: * entries in the hash table exceeds the product of the load factor and the
0057: * current capacity, the capacity is roughly doubled by calling the
0058: * <tt>rehash</tt> method.
0059: *
0060: * <p>As a general rule, the default load factor (.75) offers a good tradeoff
0061: * between time and space costs. Higher values decrease the space overhead
0062: * but increase the lookup cost (reflected in most of the operations of the
0063: * <tt>HashMap</tt> class, including <tt>get</tt> and <tt>put</tt>). The
0064: * expected number of entries in the map and its load factor should be taken
0065: * into account when setting its initial capacity, so as to minimize the
0066: * number of <tt>rehash</tt> operations. If the initial capacity is greater
0067: * than the maximum number of entries divided by the load factor, no
0068: * <tt>rehash</tt> operations will ever occur.
0069: *
0070: * <p>If many mappings are to be stored in a <tt>HashMap</tt> instance,
0071: * creating it with a sufficiently large capacity will allow the mappings to
0072: * be stored more efficiently than letting it perform automatic rehashing as
0073: * needed to grow the table.
0074: *
0075: * <p><b>Note that this implementation is not synchronized.</b> If multiple
0076: * threads access this map concurrently, and at least one of the threads
0077: * modifies the map structurally, it <i>must</i> be synchronized externally.
0078: * (A structural modification is any operation that adds or deletes one or
0079: * more mappings; merely changing the value associated with a key that an
0080: * instance already contains is not a structural modification.) This is
0081: * typically accomplished by synchronizing on some object that naturally
0082: * encapsulates the map. If no such object exists, the map should be
0083: * "wrapped" using the <tt>Collections.synchronizedMap</tt> method. This is
0084: * best done at creation time, to prevent accidental unsynchronized access to
0085: * the map: <pre> Map m = Collections.synchronizedMap(new HashMap(...));
0086: * </pre>
0087: *
0088: * <p>The iterators returned by all of this class's "collection view methods"
0089: * are <i>fail-fast</i>: if the map is structurally modified at any time after
0090: * the iterator is created, in any way except through the iterator's own
0091: * <tt>remove</tt> or <tt>add</tt> methods, the iterator will throw a
0092: * <tt>ConcurrentModificationException</tt>. Thus, in the face of concurrent
0093: * modification, the iterator fails quickly and cleanly, rather than risking
0094: * arbitrary, non-deterministic behavior at an undetermined time in the
0095: * future.
0096: *
0097: * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
0098: * as it is, generally speaking, impossible to make any hard guarantees in the
0099: * presence of unsynchronized concurrent modification. Fail-fast iterators
0100: * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
0101: * Therefore, it would be wrong to write a program that depended on this
0102: * exception for its correctness: <i>the fail-fast behavior of iterators
0103: * should be used only to detect bugs.</i>
0104: *
0105: * <p>This class is a member of the
0106: * <a href="{@docRoot}/../guide/collections/index.html">
0107: * Java Collections Framework</a>.
0108: *
0109: * @author Doug Lea
0110: * @author Josh Bloch
0111: * @author Arthur van Hoff
0112: * @version 1.38, 02/02/00
0113: * @see Object#hashCode()
0114: * @see Collection
0115: * @see Map
0116: * @see TreeMap
0117: * @see Hashtable
0118: * @since 1.2
0119: */
0120:
0121: public class HashMap extends AbstractMap implements Map, Cloneable,
0122: Serializable {
0123: /**
0124: * The default initial capacity - MUST be a power of two.
0125: */
0126: static final int DEFAULT_INITIAL_CAPACITY = 16;
0127:
0128: /**
0129: * The maximum capacity, used if a higher value is implicitly specified
0130: * by either of the constructors with arguments.
0131: * MUST be a power of two <= 1<<30.
0132: */
0133: static final int MAXIMUM_CAPACITY = 1 << 30;
0134:
0135: /**
0136: * The load factor used when none specified in constructor.
0137: **/
0138: static final float DEFAULT_LOAD_FACTOR = 0.75f;
0139:
0140: /**
0141: * The table, resized as necessary. Length MUST Always be a power of two.
0142: */
0143: transient Entry[] table;
0144:
0145: /**
0146: * The number of key-value mappings contained in this identity hash map.
0147: */
0148: transient int size;
0149:
0150: /**
0151: * The next size value at which to resize (capacity * load factor).
0152: * @serial
0153: */
0154: int threshold;
0155:
0156: /**
0157: * The load factor for the hash table.
0158: *
0159: * @serial
0160: */
0161: final float loadFactor;
0162:
0163: /**
0164: * The number of times this HashMap has been structurally modified
0165: * Structural modifications are those that change the number of mappings in
0166: * the HashMap or otherwise modify its internal structure (e.g.,
0167: * rehash). This field is used to make iterators on Collection-views of
0168: * the HashMap fail-fast. (See ConcurrentModificationException).
0169: */
0170: transient volatile int modCount;
0171:
0172: /**
0173: * Constructs an empty <tt>HashMap</tt> with the specified initial
0174: * capacity and load factor.
0175: *
0176: * @param initialCapacity The initial capacity.
0177: * @param loadFactor The load factor.
0178: * @throws IllegalArgumentException if the initial capacity is negative
0179: * or the load factor is nonpositive.
0180: */
0181: public HashMap(int initialCapacity, float loadFactor) {
0182: if (initialCapacity < 0)
0183: throw new IllegalArgumentException(
0184: "Illegal initial capacity: " + initialCapacity);
0185: if (initialCapacity > MAXIMUM_CAPACITY)
0186: initialCapacity = MAXIMUM_CAPACITY;
0187: if (loadFactor <= 0 || Float.isNaN(loadFactor))
0188: throw new IllegalArgumentException("Illegal load factor: "
0189: + loadFactor);
0190:
0191: // Find a power of 2 >= initialCapacity
0192: int capacity = 1;
0193: while (capacity < initialCapacity)
0194: capacity <<= 1;
0195:
0196: this .loadFactor = loadFactor;
0197: threshold = (int) (capacity * loadFactor);
0198: table = new Entry[capacity];
0199: init();
0200: }
0201:
0202: /**
0203: * Constructs an empty <tt>HashMap</tt> with the specified initial
0204: * capacity and the default load factor (0.75).
0205: *
0206: * @param initialCapacity the initial capacity.
0207: * @throws IllegalArgumentException if the initial capacity is negative.
0208: */
0209: public HashMap(int initialCapacity) {
0210: this (initialCapacity, DEFAULT_LOAD_FACTOR);
0211: }
0212:
0213: /**
0214: * Constructs an empty <tt>HashMap</tt> with the default initial capacity
0215: * (16) and the default load factor (0.75).
0216: */
0217: public HashMap() {
0218: this .loadFactor = DEFAULT_LOAD_FACTOR;
0219: threshold = (int) (DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
0220: table = new Entry[DEFAULT_INITIAL_CAPACITY];
0221: init();
0222: }
0223:
0224: /**
0225: * Constructs a new <tt>HashMap</tt> with the same mappings as the
0226: * specified <tt>Map</tt>. The <tt>HashMap</tt> is created with
0227: * default load factor (0.75) and an initial capacity sufficient to
0228: * hold the mappings in the specified <tt>Map</tt>.
0229: *
0230: * @param m the map whose mappings are to be placed in this map.
0231: * @throws NullPointerException if the specified map is null.
0232: */
0233: public HashMap(Map m) {
0234: this (Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
0235: DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
0236: putAllForCreate(m);
0237: }
0238:
0239: // internal utilities
0240:
0241: /**
0242: * Initialization hook for subclasses. This method is called
0243: * in all constructors and pseudo-constructors (clone, readObject)
0244: * after HashMap has been initialized but before any entries have
0245: * been inserted. (In the absence of this method, readObject would
0246: * require explicit knowledge of subclasses.)
0247: */
0248: void init() {
0249: }
0250:
0251: /**
0252: * Value representing null keys inside tables.
0253: */
0254: static final Object NULL_KEY = new Object();
0255:
0256: /**
0257: * Returns internal representation for key. Use NULL_KEY if key is null.
0258: */
0259: static Object maskNull(Object key) {
0260: return (key == null ? NULL_KEY : key);
0261: }
0262:
0263: /**
0264: * Returns key represented by specified internal representation.
0265: */
0266: static Object unmaskNull(Object key) {
0267: return (key == NULL_KEY ? null : key);
0268: }
0269:
0270: /**
0271: * Returns a hash value for the specified object. In addition to
0272: * the object's own hashCode, this method applies a "supplemental
0273: * hash function," which defends against poor quality hash functions.
0274: * This is critical because HashMap uses power-of two length
0275: * hash tables.<p>
0276: *
0277: * The shift distances in this function were chosen as the result
0278: * of an automated search over the entire four-dimensional search space.
0279: */
0280: static int hash(Object x) {
0281: int h = x.hashCode();
0282:
0283: h += ~(h << 9);
0284: h ^= (h >>> 14);
0285: h += (h << 4);
0286: h ^= (h >>> 10);
0287: return h;
0288: }
0289:
0290: /**
0291: * Check for equality of non-null reference x and possibly-null y.
0292: */
0293: static boolean eq(Object x, Object y) {
0294: return x == y || x.equals(y);
0295: }
0296:
0297: /**
0298: * Returns index for hash code h.
0299: */
0300: static int indexFor(int h, int length) {
0301: return h & (length - 1);
0302: }
0303:
0304: /**
0305: * Returns the number of key-value mappings in this map.
0306: *
0307: * @return the number of key-value mappings in this map.
0308: */
0309: public int size() {
0310: return size;
0311: }
0312:
0313: /**
0314: * Returns <tt>true</tt> if this map contains no key-value mappings.
0315: *
0316: * @return <tt>true</tt> if this map contains no key-value mappings.
0317: */
0318: public boolean isEmpty() {
0319: return size == 0;
0320: }
0321:
0322: /**
0323: * Returns the value to which the specified key is mapped in this identity
0324: * hash map, or <tt>null</tt> if the map contains no mapping for this key.
0325: * A return value of <tt>null</tt> does not <i>necessarily</i> indicate
0326: * that the map contains no mapping for the key; it is also possible that
0327: * the map explicitly maps the key to <tt>null</tt>. The
0328: * <tt>containsKey</tt> method may be used to distinguish these two cases.
0329: *
0330: * @param key the key whose associated value is to be returned.
0331: * @return the value to which this map maps the specified key, or
0332: * <tt>null</tt> if the map contains no mapping for this key.
0333: * @see #put(Object, Object)
0334: */
0335: public Object get(Object key) {
0336: Object k = maskNull(key);
0337: int hash = hash(k);
0338: int i = indexFor(hash, table.length);
0339: Entry e = table[i];
0340: while (true) {
0341: if (e == null)
0342: return e;
0343: if (e.hash == hash && eq(k, e.key))
0344: return e.value;
0345: e = e.next;
0346: }
0347: }
0348:
0349: /**
0350: * Returns <tt>true</tt> if this map contains a mapping for the
0351: * specified key.
0352: *
0353: * @param key The key whose presence in this map is to be tested
0354: * @return <tt>true</tt> if this map contains a mapping for the specified
0355: * key.
0356: */
0357: public boolean containsKey(Object key) {
0358: Object k = maskNull(key);
0359: int hash = hash(k);
0360: int i = indexFor(hash, table.length);
0361: Entry e = table[i];
0362: while (e != null) {
0363: if (e.hash == hash && eq(k, e.key))
0364: return true;
0365: e = e.next;
0366: }
0367: return false;
0368: }
0369:
0370: /**
0371: * Returns the entry associated with the specified key in the
0372: * HashMap. Returns null if the HashMap contains no mapping
0373: * for this key.
0374: */
0375: Entry getEntry(Object key) {
0376: Object k = maskNull(key);
0377: int hash = hash(k);
0378: int i = indexFor(hash, table.length);
0379: Entry e = table[i];
0380: while (e != null && !(e.hash == hash && eq(k, e.key)))
0381: e = e.next;
0382: return e;
0383: }
0384:
0385: /**
0386: * Associates the specified value with the specified key in this map.
0387: * If the map previously contained a mapping for this key, the old
0388: * value is replaced.
0389: *
0390: * @param key key with which the specified value is to be associated.
0391: * @param value value to be associated with the specified key.
0392: * @return previous value associated with specified key, or <tt>null</tt>
0393: * if there was no mapping for key. A <tt>null</tt> return can
0394: * also indicate that the HashMap previously associated
0395: * <tt>null</tt> with the specified key.
0396: */
0397: public Object put(Object key, Object value) {
0398: Object k = maskNull(key);
0399: int hash = hash(k);
0400: int i = indexFor(hash, table.length);
0401:
0402: for (Entry e = table[i]; e != null; e = e.next) {
0403: if (e.hash == hash && eq(k, e.key)) {
0404: Object oldValue = e.value;
0405: e.value = value;
0406: e.recordAccess(this );
0407: return oldValue;
0408: }
0409: }
0410:
0411: modCount++;
0412: addEntry(hash, k, value, i);
0413: return null;
0414: }
0415:
0416: /**
0417: * This method is used instead of put by constructors and
0418: * pseudoconstructors (clone, readObject). It does not resize the table,
0419: * check for comodification, etc. It calls createEntry rather than
0420: * addEntry.
0421: */
0422: private void putForCreate(Object key, Object value) {
0423: Object k = maskNull(key);
0424: int hash = hash(k);
0425: int i = indexFor(hash, table.length);
0426:
0427: /**
0428: * Look for preexisting entry for key. This will never happen for
0429: * clone or deserialize. It will only happen for construction if the
0430: * input Map is a sorted map whose ordering is inconsistent w/ equals.
0431: */
0432: for (Entry e = table[i]; e != null; e = e.next) {
0433: if (e.hash == hash && eq(k, e.key)) {
0434: e.value = value;
0435: return;
0436: }
0437: }
0438:
0439: createEntry(hash, k, value, i);
0440: }
0441:
0442: void putAllForCreate(Map m) {
0443: for (Iterator i = m.entrySet().iterator(); i.hasNext();) {
0444: Map.Entry e = (Map.Entry) i.next();
0445: putForCreate(e.getKey(), e.getValue());
0446: }
0447: }
0448:
0449: /**
0450: * Rehashes the contents of this map into a new array with a
0451: * larger capacity. This method is called automatically when the
0452: * number of keys in this map reaches its threshold.
0453: *
0454: * If current capacity is MAXIMUM_CAPACITY, this method does not
0455: * resize the map, but but sets threshold to Integer.MAX_VALUE.
0456: * This has the effect of preventing future calls.
0457: *
0458: * @param newCapacity the new capacity, MUST be a power of two;
0459: * must be greater than current capacity unless current
0460: * capacity is MAXIMUM_CAPACITY (in which case value
0461: * is irrelevant).
0462: */
0463: void resize(int newCapacity) {
0464: Entry[] oldTable = table;
0465: int oldCapacity = oldTable.length;
0466: if (oldCapacity == MAXIMUM_CAPACITY) {
0467: threshold = Integer.MAX_VALUE;
0468: return;
0469: }
0470:
0471: Entry[] newTable = new Entry[newCapacity];
0472: transfer(newTable);
0473: table = newTable;
0474: threshold = (int) (newCapacity * loadFactor);
0475: }
0476:
0477: /**
0478: * Transfer all entries from current table to newTable.
0479: */
0480: void transfer(Entry[] newTable) {
0481: Entry[] src = table;
0482: int newCapacity = newTable.length;
0483: for (int j = 0; j < src.length; j++) {
0484: Entry e = src[j];
0485: if (e != null) {
0486: src[j] = null;
0487: do {
0488: Entry next = e.next;
0489: int i = indexFor(e.hash, newCapacity);
0490: e.next = newTable[i];
0491: newTable[i] = e;
0492: e = next;
0493: } while (e != null);
0494: }
0495: }
0496: }
0497:
0498: /**
0499: * Copies all of the mappings from the specified map to this map
0500: * These mappings will replace any mappings that
0501: * this map had for any of the keys currently in the specified map.
0502: *
0503: * @param m mappings to be stored in this map.
0504: * @throws NullPointerException if the specified map is null.
0505: */
0506: public void putAll(Map m) {
0507: int numKeysToBeAdded = m.size();
0508: if (numKeysToBeAdded == 0)
0509: return;
0510:
0511: /*
0512: * Expand the map if the map if the number of mappings to be added
0513: * is greater than or equal to threshold. This is conservative; the
0514: * obvious condition is (m.size() + size) >= threshold, but this
0515: * condition could result in a map with twice the appropriate capacity,
0516: * if the keys to be added overlap with the keys already in this map.
0517: * By using the conservative calculation, we subject ourself
0518: * to at most one extra resize.
0519: */
0520: if (numKeysToBeAdded > threshold) {
0521: int targetCapacity = (int) (numKeysToBeAdded / loadFactor + 1);
0522: if (targetCapacity > MAXIMUM_CAPACITY)
0523: targetCapacity = MAXIMUM_CAPACITY;
0524: int newCapacity = table.length;
0525: while (newCapacity < targetCapacity)
0526: newCapacity <<= 1;
0527: if (newCapacity > table.length)
0528: resize(newCapacity);
0529: }
0530:
0531: for (Iterator i = m.entrySet().iterator(); i.hasNext();) {
0532: Map.Entry e = (Map.Entry) i.next();
0533: put(e.getKey(), e.getValue());
0534: }
0535: }
0536:
0537: /**
0538: * Removes the mapping for this key from this map if present.
0539: *
0540: * @param key key whose mapping is to be removed from the map.
0541: * @return previous value associated with specified key, or <tt>null</tt>
0542: * if there was no mapping for key. A <tt>null</tt> return can
0543: * also indicate that the map previously associated <tt>null</tt>
0544: * with the specified key.
0545: */
0546: public Object remove(Object key) {
0547: Entry e = removeEntryForKey(key);
0548: return (e == null ? e : e.value);
0549: }
0550:
0551: /**
0552: * Removes and returns the entry associated with the specified key
0553: * in the HashMap. Returns null if the HashMap contains no mapping
0554: * for this key.
0555: */
0556: Entry removeEntryForKey(Object key) {
0557: Object k = maskNull(key);
0558: int hash = hash(k);
0559: int i = indexFor(hash, table.length);
0560: Entry prev = table[i];
0561: Entry e = prev;
0562:
0563: while (e != null) {
0564: Entry next = e.next;
0565: if (e.hash == hash && eq(k, e.key)) {
0566: modCount++;
0567: size--;
0568: if (prev == e)
0569: table[i] = next;
0570: else
0571: prev.next = next;
0572: e.recordRemoval(this );
0573: return e;
0574: }
0575: prev = e;
0576: e = next;
0577: }
0578:
0579: return e;
0580: }
0581:
0582: /**
0583: * Special version of remove for EntrySet.
0584: */
0585: Entry removeMapping(Object o) {
0586: if (!(o instanceof Map.Entry))
0587: return null;
0588:
0589: Map.Entry entry = (Map.Entry) o;
0590: Object k = maskNull(entry.getKey());
0591: int hash = hash(k);
0592: int i = indexFor(hash, table.length);
0593: Entry prev = table[i];
0594: Entry e = prev;
0595:
0596: while (e != null) {
0597: Entry next = e.next;
0598: if (e.hash == hash && e.equals(entry)) {
0599: modCount++;
0600: size--;
0601: if (prev == e)
0602: table[i] = next;
0603: else
0604: prev.next = next;
0605: e.recordRemoval(this );
0606: return e;
0607: }
0608: prev = e;
0609: e = next;
0610: }
0611:
0612: return e;
0613: }
0614:
0615: /**
0616: * Removes all mappings from this map.
0617: */
0618: public void clear() {
0619: modCount++;
0620: Entry tab[] = table;
0621: for (int i = 0; i < tab.length; i++)
0622: tab[i] = null;
0623: size = 0;
0624: }
0625:
0626: /**
0627: * Returns <tt>true</tt> if this map maps one or more keys to the
0628: * specified value.
0629: *
0630: * @param value value whose presence in this map is to be tested.
0631: * @return <tt>true</tt> if this map maps one or more keys to the
0632: * specified value.
0633: */
0634: public boolean containsValue(Object value) {
0635: if (value == null)
0636: return containsNullValue();
0637:
0638: Entry tab[] = table;
0639: for (int i = 0; i < tab.length; i++)
0640: for (Entry e = tab[i]; e != null; e = e.next)
0641: if (value.equals(e.value))
0642: return true;
0643: return false;
0644: }
0645:
0646: /**
0647: * Special-case code for containsValue with null argument
0648: **/
0649: private boolean containsNullValue() {
0650: Entry tab[] = table;
0651: for (int i = 0; i < tab.length; i++)
0652: for (Entry e = tab[i]; e != null; e = e.next)
0653: if (e.value == null)
0654: return true;
0655: return false;
0656: }
0657:
0658: /**
0659: * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
0660: * values themselves are not cloned.
0661: *
0662: * @return a shallow copy of this map.
0663: */
0664: public Object clone() {
0665: HashMap result = null;
0666: try {
0667: result = (HashMap) super .clone();
0668: } catch (CloneNotSupportedException e) {
0669: // assert false;
0670: }
0671: result.table = new Entry[table.length];
0672: result.entrySet = null;
0673: result.modCount = 0;
0674: result.size = 0;
0675: result.init();
0676: result.putAllForCreate(this );
0677:
0678: return result;
0679: }
0680:
0681: static class Entry implements Map.Entry {
0682: final Object key;
0683: Object value;
0684: final int hash;
0685: Entry next;
0686:
0687: /**
0688: * Create new entry.
0689: */
0690: Entry(int h, Object k, Object v, Entry n) {
0691: value = v;
0692: next = n;
0693: key = k;
0694: hash = h;
0695: }
0696:
0697: public Object getKey() {
0698: return unmaskNull(key);
0699: }
0700:
0701: public Object getValue() {
0702: return value;
0703: }
0704:
0705: public Object setValue(Object newValue) {
0706: Object oldValue = value;
0707: value = newValue;
0708: return oldValue;
0709: }
0710:
0711: public boolean equals(Object o) {
0712: if (!(o instanceof Map.Entry))
0713: return false;
0714: Map.Entry e = (Map.Entry) o;
0715: Object k1 = getKey();
0716: Object k2 = e.getKey();
0717: if (k1 == k2 || (k1 != null && k1.equals(k2))) {
0718: Object v1 = getValue();
0719: Object v2 = e.getValue();
0720: if (v1 == v2 || (v1 != null && v1.equals(v2)))
0721: return true;
0722: }
0723: return false;
0724: }
0725:
0726: public int hashCode() {
0727: return (key == NULL_KEY ? 0 : key.hashCode())
0728: ^ (value == null ? 0 : value.hashCode());
0729: }
0730:
0731: public String toString() {
0732: return getKey() + "=" + getValue();
0733: }
0734:
0735: /**
0736: * This method is invoked whenever the value in an entry is
0737: * overwritten by an invocation of put(k,v) for a key k that's already
0738: * in the HashMap.
0739: */
0740: void recordAccess(HashMap m) {
0741: }
0742:
0743: /**
0744: * This method is invoked whenever the entry is
0745: * removed from the table.
0746: */
0747: void recordRemoval(HashMap m) {
0748: }
0749: }
0750:
0751: /**
0752: * Add a new entry with the specified key, value and hash code to
0753: * the specified bucket. It is the responsibility of this
0754: * method to resize the table if appropriate.
0755: *
0756: * Subclass overrides this to alter the behavior of put method.
0757: */
0758: void addEntry(int hash, Object key, Object value, int bucketIndex) {
0759: table[bucketIndex] = new Entry(hash, key, value,
0760: table[bucketIndex]);
0761: if (size++ >= threshold)
0762: resize(2 * table.length);
0763: }
0764:
0765: /**
0766: * Like addEntry except that this version is used when creating entries
0767: * as part of Map construction or "pseudo-construction" (cloning,
0768: * deserialization). This version needn't worry about resizing the table.
0769: *
0770: * Subclass overrides this to alter the behavior of HashMap(Map),
0771: * clone, and readObject.
0772: */
0773: void createEntry(int hash, Object key, Object value, int bucketIndex) {
0774: table[bucketIndex] = new Entry(hash, key, value,
0775: table[bucketIndex]);
0776: size++;
0777: }
0778:
0779: private abstract class HashIterator implements Iterator {
0780: Entry next; // next entry to return
0781: int expectedModCount; // For fast-fail
0782: int index; // current slot
0783: Entry current; // current entry
0784:
0785: HashIterator() {
0786: expectedModCount = modCount;
0787: Entry[] t = table;
0788: int i = t.length;
0789: Entry n = null;
0790: if (size != 0) { // advance to first entry
0791: while (i > 0 && (n = t[--i]) == null)
0792: ;
0793: }
0794: next = n;
0795: index = i;
0796: }
0797:
0798: public boolean hasNext() {
0799: return next != null;
0800: }
0801:
0802: Entry nextEntry() {
0803: if (modCount != expectedModCount)
0804: throw new ConcurrentModificationException();
0805: Entry e = next;
0806: if (e == null)
0807: throw new NoSuchElementException();
0808:
0809: Entry n = e.next;
0810: Entry[] t = table;
0811: int i = index;
0812: while (n == null && i > 0)
0813: n = t[--i];
0814: index = i;
0815: next = n;
0816: return current = e;
0817: }
0818:
0819: public void remove() {
0820: if (current == null)
0821: throw new IllegalStateException();
0822: if (modCount != expectedModCount)
0823: throw new ConcurrentModificationException();
0824: Object k = current.key;
0825: current = null;
0826: HashMap.this .removeEntryForKey(k);
0827: expectedModCount = modCount;
0828: }
0829:
0830: }
0831:
0832: private class ValueIterator extends HashIterator {
0833: public Object next() {
0834: return nextEntry().value;
0835: }
0836: }
0837:
0838: private class KeyIterator extends HashIterator {
0839: public Object next() {
0840: return nextEntry().getKey();
0841: }
0842: }
0843:
0844: private class EntryIterator extends HashIterator {
0845: public Object next() {
0846: return nextEntry();
0847: }
0848: }
0849:
0850: // Subclass overrides these to alter behavior of views' iterator() method
0851: Iterator newKeyIterator() {
0852: return new KeyIterator();
0853: }
0854:
0855: Iterator newValueIterator() {
0856: return new ValueIterator();
0857: }
0858:
0859: Iterator newEntryIterator() {
0860: return new EntryIterator();
0861: }
0862:
0863: // Views
0864:
0865: private transient Set entrySet = null;
0866:
0867: /**
0868: * Returns a set view of the keys contained in this map. The set is
0869: * backed by the map, so changes to the map are reflected in the set, and
0870: * vice-versa. The set supports element removal, which removes the
0871: * corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
0872: * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
0873: * <tt>clear</tt> operations. It does not support the <tt>add</tt> or
0874: * <tt>addAll</tt> operations.
0875: *
0876: * @return a set view of the keys contained in this map.
0877: */
0878: public Set keySet() {
0879: Set ks = keySet;
0880: return (ks != null ? ks : (keySet = new KeySet()));
0881: }
0882:
0883: private class KeySet extends AbstractSet {
0884: public Iterator iterator() {
0885: return newKeyIterator();
0886: }
0887:
0888: public int size() {
0889: return size;
0890: }
0891:
0892: public boolean contains(Object o) {
0893: return containsKey(o);
0894: }
0895:
0896: public boolean remove(Object o) {
0897: return HashMap.this .removeEntryForKey(o) != null;
0898: }
0899:
0900: public void clear() {
0901: HashMap.this .clear();
0902: }
0903: }
0904:
0905: /**
0906: * Returns a collection view of the values contained in this map. The
0907: * collection is backed by the map, so changes to the map are reflected in
0908: * the collection, and vice-versa. The collection supports element
0909: * removal, which removes the corresponding mapping from this map, via the
0910: * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
0911: * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
0912: * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
0913: *
0914: * @return a collection view of the values contained in this map.
0915: */
0916: public Collection values() {
0917: Collection vs = values;
0918: return (vs != null ? vs : (values = new Values()));
0919: }
0920:
0921: private class Values extends AbstractCollection {
0922: public Iterator iterator() {
0923: return newValueIterator();
0924: }
0925:
0926: public int size() {
0927: return size;
0928: }
0929:
0930: public boolean contains(Object o) {
0931: return containsValue(o);
0932: }
0933:
0934: public void clear() {
0935: HashMap.this .clear();
0936: }
0937: }
0938:
0939: /**
0940: * Returns a collection view of the mappings contained in this map. Each
0941: * element in the returned collection is a <tt>Map.Entry</tt>. The
0942: * collection is backed by the map, so changes to the map are reflected in
0943: * the collection, and vice-versa. The collection supports element
0944: * removal, which removes the corresponding mapping from the map, via the
0945: * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
0946: * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
0947: * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
0948: *
0949: * @return a collection view of the mappings contained in this map.
0950: * @see Map.Entry
0951: */
0952: public Set entrySet() {
0953: Set es = entrySet;
0954: return (es != null ? es : (entrySet = new EntrySet()));
0955: }
0956:
0957: private class EntrySet extends AbstractSet {
0958: public Iterator iterator() {
0959: return newEntryIterator();
0960: }
0961:
0962: public boolean contains(Object o) {
0963: if (!(o instanceof Map.Entry))
0964: return false;
0965: Map.Entry e = (Map.Entry) o;
0966: Entry candidate = getEntry(e.getKey());
0967: return candidate != null && candidate.equals(e);
0968: }
0969:
0970: public boolean remove(Object o) {
0971: return removeMapping(o) != null;
0972: }
0973:
0974: public int size() {
0975: return size;
0976: }
0977:
0978: public void clear() {
0979: HashMap.this .clear();
0980: }
0981: }
0982:
0983: /**
0984: * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
0985: * serialize it).
0986: *
0987: * @serialData The <i>capacity</i> of the HashMap (the length of the
0988: * bucket array) is emitted (int), followed by the
0989: * <i>size</i> of the HashMap (the number of key-value
0990: * mappings), followed by the key (Object) and value (Object)
0991: * for each key-value mapping represented by the HashMap
0992: * The key-value mappings are emitted in the order that they
0993: * are returned by <tt>entrySet().iterator()</tt>.
0994: *
0995: */
0996: private void writeObject(java.io.ObjectOutputStream s)
0997: throws IOException {
0998: // Write out the threshold, loadfactor, and any hidden stuff
0999: s.defaultWriteObject();
1000:
1001: // Write out number of buckets
1002: s.writeInt(table.length);
1003:
1004: // Write out size (number of Mappings)
1005: s.writeInt(size);
1006:
1007: // Write out keys and values (alternating)
1008: for (Iterator i = entrySet().iterator(); i.hasNext();) {
1009: Map.Entry e = (Map.Entry) i.next();
1010: s.writeObject(e.getKey());
1011: s.writeObject(e.getValue());
1012: }
1013: }
1014:
1015: private static final long serialVersionUID = 362498820763181265L;
1016:
1017: /**
1018: * Reconstitute the <tt>HashMap</tt> instance from a stream (i.e.,
1019: * deserialize it).
1020: */
1021: private void readObject(java.io.ObjectInputStream s)
1022: throws IOException, ClassNotFoundException {
1023: // Read in the threshold, loadfactor, and any hidden stuff
1024: s.defaultReadObject();
1025:
1026: // Read in number of buckets and allocate the bucket array;
1027: int numBuckets = s.readInt();
1028: table = new Entry[numBuckets];
1029:
1030: init(); // Give subclass a chance to do its thing.
1031:
1032: // Read in size (number of Mappings)
1033: int size = s.readInt();
1034:
1035: // Read the keys and values, and put the mappings in the HashMap
1036: for (int i = 0; i < size; i++) {
1037: Object key = s.readObject();
1038: Object value = s.readObject();
1039: putForCreate(key, value);
1040: }
1041: }
1042:
1043: // These methods are used when serializing HashSets
1044: int capacity() {
1045: return table.length;
1046: }
1047:
1048: float loadFactor() {
1049: return loadFactor;
1050: }
1051: }
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