| /* |
| * Copyright (C) 2014 The Android Open Source Project |
| * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.util; |
| import java.io.*; |
| |
| /** |
| * Hash table based implementation of the <tt>Map</tt> interface. This |
| * implementation provides all of the optional map operations, and permits |
| * <tt>null</tt> values and the <tt>null</tt> key. (The <tt>HashMap</tt> |
| * class is roughly equivalent to <tt>Hashtable</tt>, except that it is |
| * unsynchronized and permits nulls.) This class makes no guarantees as to |
| * the order of the map; in particular, it does not guarantee that the order |
| * will remain constant over time. |
| * |
| * <p>This implementation provides constant-time performance for the basic |
| * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function |
| * disperses the elements properly among the buckets. Iteration over |
| * collection views requires time proportional to the "capacity" of the |
| * <tt>HashMap</tt> instance (the number of buckets) plus its size (the number |
| * of key-value mappings). Thus, it's very important not to set the initial |
| * capacity too high (or the load factor too low) if iteration performance is |
| * important. |
| * |
| * <p>An instance of <tt>HashMap</tt> has two parameters that affect its |
| * performance: <i>initial capacity</i> and <i>load factor</i>. The |
| * <i>capacity</i> is the number of buckets in the hash table, and the initial |
| * capacity is simply the capacity at the time the hash table is created. The |
| * <i>load factor</i> is a measure of how full the hash table is allowed to |
| * get before its capacity is automatically increased. When the number of |
| * entries in the hash table exceeds the product of the load factor and the |
| * current capacity, the hash table is <i>rehashed</i> (that is, internal data |
| * structures are rebuilt) so that the hash table has approximately twice the |
| * number of buckets. |
| * |
| * <p>As a general rule, the default load factor (.75) offers a good tradeoff |
| * between time and space costs. Higher values decrease the space overhead |
| * but increase the lookup cost (reflected in most of the operations of the |
| * <tt>HashMap</tt> class, including <tt>get</tt> and <tt>put</tt>). The |
| * expected number of entries in the map and its load factor should be taken |
| * into account when setting its initial capacity, so as to minimize the |
| * number of rehash operations. If the initial capacity is greater |
| * than the maximum number of entries divided by the load factor, no |
| * rehash operations will ever occur. |
| * |
| * <p>If many mappings are to be stored in a <tt>HashMap</tt> instance, |
| * creating it with a sufficiently large capacity will allow the mappings to |
| * be stored more efficiently than letting it perform automatic rehashing as |
| * needed to grow the table. |
| * |
| * <p><strong>Note that this implementation is not synchronized.</strong> |
| * If multiple threads access a hash map concurrently, and at least one of |
| * the threads modifies the map structurally, it <i>must</i> be |
| * synchronized externally. (A structural modification is any operation |
| * that adds or deletes one or more mappings; merely changing the value |
| * associated with a key that an instance already contains is not a |
| * structural modification.) This is typically accomplished by |
| * synchronizing on some object that naturally encapsulates the map. |
| * |
| * If no such object exists, the map should be "wrapped" using the |
| * {@link Collections#synchronizedMap Collections.synchronizedMap} |
| * method. This is best done at creation time, to prevent accidental |
| * unsynchronized access to the map:<pre> |
| * Map m = Collections.synchronizedMap(new HashMap(...));</pre> |
| * |
| * <p>The iterators returned by all of this class's "collection view methods" |
| * are <i>fail-fast</i>: if the map is structurally modified at any time after |
| * the iterator is created, in any way except through the iterator's own |
| * <tt>remove</tt> method, the iterator will throw a |
| * {@link ConcurrentModificationException}. Thus, in the face of concurrent |
| * modification, the iterator fails quickly and cleanly, rather than risking |
| * arbitrary, non-deterministic behavior at an undetermined time in the |
| * future. |
| * |
| * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed |
| * as it is, generally speaking, impossible to make any hard guarantees in the |
| * presence of unsynchronized concurrent modification. Fail-fast iterators |
| * throw <tt>ConcurrentModificationException</tt> on a best-effort basis. |
| * Therefore, it would be wrong to write a program that depended on this |
| * exception for its correctness: <i>the fail-fast behavior of iterators |
| * should be used only to detect bugs.</i> |
| * |
| * <p>This class is a member of the |
| * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @param <K> the type of keys maintained by this map |
| * @param <V> the type of mapped values |
| * |
| * @author Doug Lea |
| * @author Josh Bloch |
| * @author Arthur van Hoff |
| * @author Neal Gafter |
| * @see Object#hashCode() |
| * @see Collection |
| * @see Map |
| * @see TreeMap |
| * @see Hashtable |
| * @since 1.2 |
| */ |
| |
| public class HashMap<K,V> |
| extends AbstractMap<K,V> |
| implements Map<K,V>, Cloneable, Serializable |
| { |
| |
| /** |
| * The default initial capacity - MUST be a power of two. |
| */ |
| static final int DEFAULT_INITIAL_CAPACITY = 1 << 4; // aka 16 |
| |
| /** |
| * The maximum capacity, used if a higher value is implicitly specified |
| * by either of the constructors with arguments. |
| * MUST be a power of two <= 1<<30. |
| */ |
| static final int MAXIMUM_CAPACITY = 1 << 30; |
| |
| /** |
| * The load factor used when none specified in constructor. |
| */ |
| static final float DEFAULT_LOAD_FACTOR = 0.75f; |
| |
| /** |
| * An empty table instance to share when the table is not inflated. |
| */ |
| static final HashMapEntry<?,?>[] EMPTY_TABLE = {}; |
| |
| /** |
| * The table, resized as necessary. Length MUST Always be a power of two. |
| */ |
| transient HashMapEntry<K,V>[] table = (HashMapEntry<K,V>[]) EMPTY_TABLE; |
| |
| /** |
| * The number of key-value mappings contained in this map. |
| */ |
| transient int size; |
| |
| /** |
| * The next size value at which to resize (capacity * load factor). |
| * @serial |
| */ |
| // If table == EMPTY_TABLE then this is the initial capacity at which the |
| // table will be created when inflated. |
| int threshold; |
| |
| /** |
| * The load factor for the hash table. |
| * |
| * @serial |
| */ |
| final float loadFactor; |
| |
| /** |
| * The number of times this HashMap has been structurally modified |
| * Structural modifications are those that change the number of mappings in |
| * the HashMap or otherwise modify its internal structure (e.g., |
| * rehash). This field is used to make iterators on Collection-views of |
| * the HashMap fail-fast. (See ConcurrentModificationException). |
| */ |
| transient int modCount; |
| |
| /** |
| * The default threshold of map capacity above which alternative hashing is |
| * used for String keys. Alternative hashing reduces the incidence of |
| * collisions due to weak hash code calculation for String keys. |
| * <p/> |
| * This value may be overridden by defining the system property |
| * {@code jdk.map.althashing.threshold}. A property value of {@code 1} |
| * forces alternative hashing to be used at all times whereas |
| * {@code -1} value ensures that alternative hashing is never used. |
| */ |
| static final int ALTERNATIVE_HASHING_THRESHOLD_DEFAULT = Integer.MAX_VALUE; |
| |
| /** |
| * holds values which can't be initialized until after VM is booted. |
| */ |
| private static class Holder { |
| |
| /** |
| * Table capacity above which to switch to use alternative hashing. |
| */ |
| static final int ALTERNATIVE_HASHING_THRESHOLD; |
| |
| static { |
| String altThreshold = java.security.AccessController.doPrivileged( |
| new sun.security.action.GetPropertyAction( |
| "jdk.map.althashing.threshold")); |
| |
| int threshold; |
| try { |
| threshold = (null != altThreshold) |
| ? Integer.parseInt(altThreshold) |
| : ALTERNATIVE_HASHING_THRESHOLD_DEFAULT; |
| |
| // disable alternative hashing if -1 |
| if (threshold == -1) { |
| threshold = Integer.MAX_VALUE; |
| } |
| |
| if (threshold < 0) { |
| throw new IllegalArgumentException("value must be positive integer."); |
| } |
| } catch(IllegalArgumentException failed) { |
| throw new Error("Illegal value for 'jdk.map.althashing.threshold'", failed); |
| } |
| |
| ALTERNATIVE_HASHING_THRESHOLD = threshold; |
| } |
| } |
| |
| /** |
| * A randomizing value associated with this instance that is applied to |
| * hash code of keys to make hash collisions harder to find. If 0 then |
| * alternative hashing is disabled. |
| */ |
| transient int hashSeed = 0; |
| |
| /** |
| * Constructs an empty <tt>HashMap</tt> with the specified initial |
| * capacity and load factor. |
| * |
| * @param initialCapacity the initial capacity |
| * @param loadFactor the load factor |
| * @throws IllegalArgumentException if the initial capacity is negative |
| * or the load factor is nonpositive |
| */ |
| public HashMap(int initialCapacity, float loadFactor) { |
| if (initialCapacity < 0) |
| throw new IllegalArgumentException("Illegal initial capacity: " + |
| initialCapacity); |
| if (initialCapacity > MAXIMUM_CAPACITY) |
| initialCapacity = MAXIMUM_CAPACITY; |
| if (loadFactor <= 0 || Float.isNaN(loadFactor)) |
| throw new IllegalArgumentException("Illegal load factor: " + |
| loadFactor); |
| |
| this.loadFactor = loadFactor; |
| threshold = initialCapacity; |
| init(); |
| } |
| |
| /** |
| * Constructs an empty <tt>HashMap</tt> with the specified initial |
| * capacity and the default load factor (0.75). |
| * |
| * @param initialCapacity the initial capacity. |
| * @throws IllegalArgumentException if the initial capacity is negative. |
| */ |
| public HashMap(int initialCapacity) { |
| this(initialCapacity, DEFAULT_LOAD_FACTOR); |
| } |
| |
| /** |
| * Constructs an empty <tt>HashMap</tt> with the default initial capacity |
| * (16) and the default load factor (0.75). |
| */ |
| public HashMap() { |
| this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR); |
| } |
| |
| /** |
| * Constructs a new <tt>HashMap</tt> with the same mappings as the |
| * specified <tt>Map</tt>. The <tt>HashMap</tt> is created with |
| * default load factor (0.75) and an initial capacity sufficient to |
| * hold the mappings in the specified <tt>Map</tt>. |
| * |
| * @param m the map whose mappings are to be placed in this map |
| * @throws NullPointerException if the specified map is null |
| */ |
| public HashMap(Map<? extends K, ? extends V> m) { |
| this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1, |
| DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR); |
| inflateTable(threshold); |
| |
| putAllForCreate(m); |
| } |
| |
| private static int roundUpToPowerOf2(int number) { |
| // assert number >= 0 : "number must be non-negative"; |
| int rounded = number >= MAXIMUM_CAPACITY |
| ? MAXIMUM_CAPACITY |
| : (rounded = Integer.highestOneBit(number)) != 0 |
| ? (Integer.bitCount(number) > 1) ? rounded << 1 : rounded |
| : 1; |
| |
| return rounded; |
| } |
| |
| /** |
| * Inflates the table. |
| */ |
| private void inflateTable(int toSize) { |
| // Find a power of 2 >= toSize |
| int capacity = roundUpToPowerOf2(toSize); |
| |
| // Android-changed: Replace usage of Math.min() here because this method is |
| // called from the <clinit> of runtime, at which point the native libraries |
| // needed by Float.* might not be loaded. |
| float thresholdFloat = capacity * loadFactor; |
| if (thresholdFloat > MAXIMUM_CAPACITY + 1) { |
| thresholdFloat = MAXIMUM_CAPACITY + 1; |
| } |
| |
| threshold = (int) thresholdFloat; |
| table = new HashMapEntry[capacity]; |
| initHashSeedAsNeeded(capacity); |
| } |
| |
| // internal utilities |
| |
| /** |
| * Initialization hook for subclasses. This method is called |
| * in all constructors and pseudo-constructors (clone, readObject) |
| * after HashMap has been initialized but before any entries have |
| * been inserted. (In the absence of this method, readObject would |
| * require explicit knowledge of subclasses.) |
| */ |
| void init() { |
| } |
| |
| /** |
| * Initialize the hashing mask value. We defer initialization until we |
| * really need it. |
| */ |
| final boolean initHashSeedAsNeeded(int capacity) { |
| boolean currentAltHashing = hashSeed != 0; |
| boolean useAltHashing = sun.misc.VM.isBooted() && |
| (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD); |
| boolean switching = currentAltHashing ^ useAltHashing; |
| if (switching) { |
| hashSeed = useAltHashing |
| ? sun.misc.Hashing.randomHashSeed(this) |
| : 0; |
| } |
| return switching; |
| } |
| |
| /** |
| * Retrieve object hash code and applies a supplemental hash function to the |
| * result hash, which defends against poor quality hash functions. This is |
| * critical because HashMap uses power-of-two length hash tables, that |
| * otherwise encounter collisions for hashCodes that do not differ |
| * in lower bits. Note: Null keys always map to hash 0, thus index 0. |
| */ |
| final int hash(Object k) { |
| int h = hashSeed; |
| if (0 != h && k instanceof String) { |
| return sun.misc.Hashing.stringHash32((String) k); |
| } |
| |
| h ^= k.hashCode(); |
| |
| // This function ensures that hashCodes that differ only by |
| // constant multiples at each bit position have a bounded |
| // number of collisions (approximately 8 at default load factor). |
| h ^= (h >>> 20) ^ (h >>> 12); |
| return h ^ (h >>> 7) ^ (h >>> 4); |
| } |
| |
| /** |
| * Returns index for hash code h. |
| */ |
| static int indexFor(int h, int length) { |
| // assert Integer.bitCount(length) == 1 : "length must be a non-zero power of 2"; |
| return h & (length-1); |
| } |
| |
| /** |
| * Returns the number of key-value mappings in this map. |
| * |
| * @return the number of key-value mappings in this map |
| */ |
| public int size() { |
| return size; |
| } |
| |
| /** |
| * Returns <tt>true</tt> if this map contains no key-value mappings. |
| * |
| * @return <tt>true</tt> if this map contains no key-value mappings |
| */ |
| public boolean isEmpty() { |
| return size == 0; |
| } |
| |
| /** |
| * Returns the value to which the specified key is mapped, |
| * or {@code null} if this map contains no mapping for the key. |
| * |
| * <p>More formally, if this map contains a mapping from a key |
| * {@code k} to a value {@code v} such that {@code (key==null ? k==null : |
| * key.equals(k))}, then this method returns {@code v}; otherwise |
| * it returns {@code null}. (There can be at most one such mapping.) |
| * |
| * <p>A return value of {@code null} does not <i>necessarily</i> |
| * indicate that the map contains no mapping for the key; it's also |
| * possible that the map explicitly maps the key to {@code null}. |
| * The {@link #containsKey containsKey} operation may be used to |
| * distinguish these two cases. |
| * |
| * @see #put(Object, Object) |
| */ |
| public V get(Object key) { |
| if (key == null) |
| return getForNullKey(); |
| Entry<K,V> entry = getEntry(key); |
| |
| return null == entry ? null : entry.getValue(); |
| } |
| |
| /** |
| * Offloaded version of get() to look up null keys. Null keys map |
| * to index 0. This null case is split out into separate methods |
| * for the sake of performance in the two most commonly used |
| * operations (get and put), but incorporated with conditionals in |
| * others. |
| */ |
| private V getForNullKey() { |
| if (size == 0) { |
| return null; |
| } |
| for (HashMapEntry<K,V> e = table[0]; e != null; e = e.next) { |
| if (e.key == null) |
| return e.value; |
| } |
| return null; |
| } |
| |
| /** |
| * Returns <tt>true</tt> if this map contains a mapping for the |
| * specified key. |
| * |
| * @param key The key whose presence in this map is to be tested |
| * @return <tt>true</tt> if this map contains a mapping for the specified |
| * key. |
| */ |
| public boolean containsKey(Object key) { |
| return getEntry(key) != null; |
| } |
| |
| /** |
| * Returns the entry associated with the specified key in the |
| * HashMap. Returns null if the HashMap contains no mapping |
| * for the key. |
| */ |
| final Entry<K,V> getEntry(Object key) { |
| if (size == 0) { |
| return null; |
| } |
| |
| int hash = (key == null) ? 0 : hash(key); |
| for (HashMapEntry<K,V> e = table[indexFor(hash, table.length)]; |
| e != null; |
| e = e.next) { |
| Object k; |
| if (e.hash == hash && |
| ((k = e.key) == key || (key != null && key.equals(k)))) |
| return e; |
| } |
| return null; |
| } |
| |
| /** |
| * Associates the specified value with the specified key in this map. |
| * If the map previously contained a mapping for the key, the old |
| * value is replaced. |
| * |
| * @param key key with which the specified value is to be associated |
| * @param value value to be associated with the specified key |
| * @return the previous value associated with <tt>key</tt>, or |
| * <tt>null</tt> if there was no mapping for <tt>key</tt>. |
| * (A <tt>null</tt> return can also indicate that the map |
| * previously associated <tt>null</tt> with <tt>key</tt>.) |
| */ |
| public V put(K key, V value) { |
| if (table == EMPTY_TABLE) { |
| inflateTable(threshold); |
| } |
| if (key == null) |
| return putForNullKey(value); |
| int hash = hash(key); |
| int i = indexFor(hash, table.length); |
| for (HashMapEntry<K,V> e = table[i]; e != null; e = e.next) { |
| Object k; |
| if (e.hash == hash && ((k = e.key) == key || key.equals(k))) { |
| V oldValue = e.value; |
| e.value = value; |
| e.recordAccess(this); |
| return oldValue; |
| } |
| } |
| |
| modCount++; |
| addEntry(hash, key, value, i); |
| return null; |
| } |
| |
| /** |
| * Offloaded version of put for null keys |
| */ |
| private V putForNullKey(V value) { |
| for (HashMapEntry<K,V> e = table[0]; e != null; e = e.next) { |
| if (e.key == null) { |
| V oldValue = e.value; |
| e.value = value; |
| e.recordAccess(this); |
| return oldValue; |
| } |
| } |
| modCount++; |
| addEntry(0, null, value, 0); |
| return null; |
| } |
| |
| /** |
| * This method is used instead of put by constructors and |
| * pseudoconstructors (clone, readObject). It does not resize the table, |
| * check for comodification, etc. It calls createEntry rather than |
| * addEntry. |
| */ |
| private void putForCreate(K key, V value) { |
| int hash = null == key ? 0 : hash(key); |
| int i = indexFor(hash, table.length); |
| |
| /** |
| * Look for preexisting entry for key. This will never happen for |
| * clone or deserialize. It will only happen for construction if the |
| * input Map is a sorted map whose ordering is inconsistent w/ equals. |
| */ |
| for (HashMapEntry<K,V> e = table[i]; e != null; e = e.next) { |
| Object k; |
| if (e.hash == hash && |
| ((k = e.key) == key || (key != null && key.equals(k)))) { |
| e.value = value; |
| return; |
| } |
| } |
| |
| createEntry(hash, key, value, i); |
| } |
| |
| private void putAllForCreate(Map<? extends K, ? extends V> m) { |
| for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
| putForCreate(e.getKey(), e.getValue()); |
| } |
| |
| /** |
| * Rehashes the contents of this map into a new array with a |
| * larger capacity. This method is called automatically when the |
| * number of keys in this map reaches its threshold. |
| * |
| * If current capacity is MAXIMUM_CAPACITY, this method does not |
| * resize the map, but sets threshold to Integer.MAX_VALUE. |
| * This has the effect of preventing future calls. |
| * |
| * @param newCapacity the new capacity, MUST be a power of two; |
| * must be greater than current capacity unless current |
| * capacity is MAXIMUM_CAPACITY (in which case value |
| * is irrelevant). |
| */ |
| void resize(int newCapacity) { |
| HashMapEntry[] oldTable = table; |
| int oldCapacity = oldTable.length; |
| if (oldCapacity == MAXIMUM_CAPACITY) { |
| threshold = Integer.MAX_VALUE; |
| return; |
| } |
| |
| HashMapEntry[] newTable = new HashMapEntry[newCapacity]; |
| transfer(newTable, initHashSeedAsNeeded(newCapacity)); |
| table = newTable; |
| threshold = (int)Math.min(newCapacity * loadFactor, MAXIMUM_CAPACITY + 1); |
| } |
| |
| /** |
| * Transfers all entries from current table to newTable. |
| */ |
| void transfer(HashMapEntry[] newTable, boolean rehash) { |
| int newCapacity = newTable.length; |
| for (HashMapEntry<K,V> e : table) { |
| while(null != e) { |
| HashMapEntry<K,V> next = e.next; |
| if (rehash) { |
| e.hash = null == e.key ? 0 : hash(e.key); |
| } |
| int i = indexFor(e.hash, newCapacity); |
| e.next = newTable[i]; |
| newTable[i] = e; |
| e = next; |
| } |
| } |
| } |
| |
| /** |
| * Copies all of the mappings from the specified map to this map. |
| * These mappings will replace any mappings that this map had for |
| * any of the keys currently in the specified map. |
| * |
| * @param m mappings to be stored in this map |
| * @throws NullPointerException if the specified map is null |
| */ |
| public void putAll(Map<? extends K, ? extends V> m) { |
| int numKeysToBeAdded = m.size(); |
| if (numKeysToBeAdded == 0) |
| return; |
| |
| if (table == EMPTY_TABLE) { |
| inflateTable((int) Math.max(numKeysToBeAdded * loadFactor, threshold)); |
| } |
| |
| /* |
| * Expand the map if the map if the number of mappings to be added |
| * is greater than or equal to threshold. This is conservative; the |
| * obvious condition is (m.size() + size) >= threshold, but this |
| * condition could result in a map with twice the appropriate capacity, |
| * if the keys to be added overlap with the keys already in this map. |
| * By using the conservative calculation, we subject ourself |
| * to at most one extra resize. |
| */ |
| if (numKeysToBeAdded > threshold) { |
| int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1); |
| if (targetCapacity > MAXIMUM_CAPACITY) |
| targetCapacity = MAXIMUM_CAPACITY; |
| int newCapacity = table.length; |
| while (newCapacity < targetCapacity) |
| newCapacity <<= 1; |
| if (newCapacity > table.length) |
| resize(newCapacity); |
| } |
| |
| for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) |
| put(e.getKey(), e.getValue()); |
| } |
| |
| /** |
| * Removes the mapping for the specified key from this map if present. |
| * |
| * @param key key whose mapping is to be removed from the map |
| * @return the previous value associated with <tt>key</tt>, or |
| * <tt>null</tt> if there was no mapping for <tt>key</tt>. |
| * (A <tt>null</tt> return can also indicate that the map |
| * previously associated <tt>null</tt> with <tt>key</tt>.) |
| */ |
| public V remove(Object key) { |
| Entry<K,V> e = removeEntryForKey(key); |
| return (e == null ? null : e.getValue()); |
| } |
| |
| /** |
| * Removes and returns the entry associated with the specified key |
| * in the HashMap. Returns null if the HashMap contains no mapping |
| * for this key. |
| */ |
| final Entry<K,V> removeEntryForKey(Object key) { |
| if (size == 0) { |
| return null; |
| } |
| int hash = (key == null) ? 0 : hash(key); |
| int i = indexFor(hash, table.length); |
| HashMapEntry<K,V> prev = table[i]; |
| HashMapEntry<K,V> e = prev; |
| |
| while (e != null) { |
| HashMapEntry<K,V> next = e.next; |
| Object k; |
| if (e.hash == hash && |
| ((k = e.key) == key || (key != null && key.equals(k)))) { |
| modCount++; |
| size--; |
| if (prev == e) |
| table[i] = next; |
| else |
| prev.next = next; |
| e.recordRemoval(this); |
| return e; |
| } |
| prev = e; |
| e = next; |
| } |
| |
| return e; |
| } |
| |
| /** |
| * Special version of remove for EntrySet using {@code Map.Entry.equals()} |
| * for matching. |
| */ |
| final Entry<K,V> removeMapping(Object o) { |
| if (size == 0 || !(o instanceof Map.Entry)) |
| return null; |
| |
| Map.Entry<K,V> entry = (Map.Entry<K,V>) o; |
| Object key = entry.getKey(); |
| int hash = (key == null) ? 0 : hash(key); |
| int i = indexFor(hash, table.length); |
| HashMapEntry<K,V> prev = table[i]; |
| HashMapEntry<K,V> e = prev; |
| |
| while (e != null) { |
| HashMapEntry<K,V> next = e.next; |
| if (e.hash == hash && e.equals(entry)) { |
| modCount++; |
| size--; |
| if (prev == e) |
| table[i] = next; |
| else |
| prev.next = next; |
| e.recordRemoval(this); |
| return e; |
| } |
| prev = e; |
| e = next; |
| } |
| |
| return e; |
| } |
| |
| /** |
| * Removes all of the mappings from this map. |
| * The map will be empty after this call returns. |
| */ |
| public void clear() { |
| modCount++; |
| Arrays.fill(table, null); |
| size = 0; |
| } |
| |
| /** |
| * Returns <tt>true</tt> if this map maps one or more keys to the |
| * specified value. |
| * |
| * @param value value whose presence in this map is to be tested |
| * @return <tt>true</tt> if this map maps one or more keys to the |
| * specified value |
| */ |
| public boolean containsValue(Object value) { |
| if (value == null) |
| return containsNullValue(); |
| |
| HashMapEntry[] tab = table; |
| for (int i = 0; i < tab.length ; i++) |
| for (HashMapEntry e = tab[i] ; e != null ; e = e.next) |
| if (value.equals(e.value)) |
| return true; |
| return false; |
| } |
| |
| /** |
| * Special-case code for containsValue with null argument |
| */ |
| private boolean containsNullValue() { |
| HashMapEntry[] tab = table; |
| for (int i = 0; i < tab.length ; i++) |
| for (HashMapEntry e = tab[i] ; e != null ; e = e.next) |
| if (e.value == null) |
| return true; |
| return false; |
| } |
| |
| /** |
| * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and |
| * values themselves are not cloned. |
| * |
| * @return a shallow copy of this map |
| */ |
| public Object clone() { |
| HashMap<K,V> result = null; |
| try { |
| result = (HashMap<K,V>)super.clone(); |
| } catch (CloneNotSupportedException e) { |
| // assert false; |
| } |
| result.table = new HashMapEntry[table.length]; |
| result.entrySet = null; |
| result.modCount = 0; |
| result.size = 0; |
| result.init(); |
| result.putAllForCreate(this); |
| |
| return result; |
| } |
| |
| /** @hide */ // Android added. |
| static class HashMapEntry<K,V> implements Map.Entry<K,V> { |
| final K key; |
| V value; |
| HashMapEntry<K,V> next; |
| int hash; |
| |
| /** |
| * Creates new entry. |
| */ |
| HashMapEntry(int h, K k, V v, HashMapEntry<K,V> n) { |
| value = v; |
| next = n; |
| key = k; |
| hash = h; |
| } |
| |
| public final K getKey() { |
| return key; |
| } |
| |
| public final V getValue() { |
| return value; |
| } |
| |
| public final V setValue(V newValue) { |
| V oldValue = value; |
| value = newValue; |
| return oldValue; |
| } |
| |
| public final boolean equals(Object o) { |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry e = (Map.Entry)o; |
| Object k1 = getKey(); |
| Object k2 = e.getKey(); |
| if (k1 == k2 || (k1 != null && k1.equals(k2))) { |
| Object v1 = getValue(); |
| Object v2 = e.getValue(); |
| if (v1 == v2 || (v1 != null && v1.equals(v2))) |
| return true; |
| } |
| return false; |
| } |
| |
| public final int hashCode() { |
| return Objects.hashCode(getKey()) ^ Objects.hashCode(getValue()); |
| } |
| |
| public final String toString() { |
| return getKey() + "=" + getValue(); |
| } |
| |
| /** |
| * This method is invoked whenever the value in an entry is |
| * overwritten by an invocation of put(k,v) for a key k that's already |
| * in the HashMap. |
| */ |
| void recordAccess(HashMap<K,V> m) { |
| } |
| |
| /** |
| * This method is invoked whenever the entry is |
| * removed from the table. |
| */ |
| void recordRemoval(HashMap<K,V> m) { |
| } |
| } |
| |
| /** |
| * Adds a new entry with the specified key, value and hash code to |
| * the specified bucket. It is the responsibility of this |
| * method to resize the table if appropriate. |
| * |
| * Subclass overrides this to alter the behavior of put method. |
| */ |
| void addEntry(int hash, K key, V value, int bucketIndex) { |
| if ((size >= threshold) && (null != table[bucketIndex])) { |
| resize(2 * table.length); |
| hash = (null != key) ? hash(key) : 0; |
| bucketIndex = indexFor(hash, table.length); |
| } |
| |
| createEntry(hash, key, value, bucketIndex); |
| } |
| |
| /** |
| * Like addEntry except that this version is used when creating entries |
| * as part of Map construction or "pseudo-construction" (cloning, |
| * deserialization). This version needn't worry about resizing the table. |
| * |
| * Subclass overrides this to alter the behavior of HashMap(Map), |
| * clone, and readObject. |
| */ |
| void createEntry(int hash, K key, V value, int bucketIndex) { |
| HashMapEntry<K,V> e = table[bucketIndex]; |
| table[bucketIndex] = new HashMapEntry<>(hash, key, value, e); |
| size++; |
| } |
| |
| private abstract class HashIterator<E> implements Iterator<E> { |
| HashMapEntry<K,V> next; // next entry to return |
| int expectedModCount; // For fast-fail |
| int index; // current slot |
| HashMapEntry<K,V> current; // current entry |
| |
| HashIterator() { |
| expectedModCount = modCount; |
| if (size > 0) { // advance to first entry |
| HashMapEntry[] t = table; |
| while (index < t.length && (next = t[index++]) == null) |
| ; |
| } |
| } |
| |
| public final boolean hasNext() { |
| return next != null; |
| } |
| |
| final Entry<K,V> nextEntry() { |
| if (modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| HashMapEntry<K,V> e = next; |
| if (e == null) |
| throw new NoSuchElementException(); |
| |
| if ((next = e.next) == null) { |
| HashMapEntry[] t = table; |
| while (index < t.length && (next = t[index++]) == null) |
| ; |
| } |
| current = e; |
| return e; |
| } |
| |
| public void remove() { |
| if (current == null) |
| throw new IllegalStateException(); |
| if (modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| Object k = current.key; |
| current = null; |
| HashMap.this.removeEntryForKey(k); |
| expectedModCount = modCount; |
| } |
| } |
| |
| private final class ValueIterator extends HashIterator<V> { |
| public V next() { |
| return nextEntry().getValue(); |
| } |
| } |
| |
| private final class KeyIterator extends HashIterator<K> { |
| public K next() { |
| return nextEntry().getKey(); |
| } |
| } |
| |
| private final class EntryIterator extends HashIterator<Map.Entry<K,V>> { |
| public Map.Entry<K,V> next() { |
| return nextEntry(); |
| } |
| } |
| |
| // Subclass overrides these to alter behavior of views' iterator() method |
| Iterator<K> newKeyIterator() { |
| return new KeyIterator(); |
| } |
| Iterator<V> newValueIterator() { |
| return new ValueIterator(); |
| } |
| Iterator<Map.Entry<K,V>> newEntryIterator() { |
| return new EntryIterator(); |
| } |
| |
| |
| // Views |
| |
| private transient Set<Map.Entry<K,V>> entrySet = null; |
| |
| /** |
| * Returns a {@link Set} view of the keys contained in this map. |
| * The set is backed by the map, so changes to the map are |
| * reflected in the set, and vice-versa. If the map is modified |
| * while an iteration over the set is in progress (except through |
| * the iterator's own <tt>remove</tt> operation), the results of |
| * the iteration are undefined. The set supports element removal, |
| * which removes the corresponding mapping from the map, via the |
| * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>, |
| * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> |
| * operations. It does not support the <tt>add</tt> or <tt>addAll</tt> |
| * operations. |
| */ |
| public Set<K> keySet() { |
| Set<K> ks = keySet; |
| return (ks != null ? ks : (keySet = new KeySet())); |
| } |
| |
| private final class KeySet extends AbstractSet<K> { |
| public Iterator<K> iterator() { |
| return newKeyIterator(); |
| } |
| public int size() { |
| return size; |
| } |
| public boolean contains(Object o) { |
| return containsKey(o); |
| } |
| public boolean remove(Object o) { |
| return HashMap.this.removeEntryForKey(o) != null; |
| } |
| public void clear() { |
| HashMap.this.clear(); |
| } |
| } |
| |
| /** |
| * Returns a {@link Collection} view of the values contained in this map. |
| * The collection is backed by the map, so changes to the map are |
| * reflected in the collection, and vice-versa. If the map is |
| * modified while an iteration over the collection is in progress |
| * (except through the iterator's own <tt>remove</tt> operation), |
| * the results of the iteration are undefined. The collection |
| * supports element removal, which removes the corresponding |
| * mapping from the map, via the <tt>Iterator.remove</tt>, |
| * <tt>Collection.remove</tt>, <tt>removeAll</tt>, |
| * <tt>retainAll</tt> and <tt>clear</tt> operations. It does not |
| * support the <tt>add</tt> or <tt>addAll</tt> operations. |
| */ |
| public Collection<V> values() { |
| Collection<V> vs = values; |
| return (vs != null ? vs : (values = new Values())); |
| } |
| |
| private final class Values extends AbstractCollection<V> { |
| public Iterator<V> iterator() { |
| return newValueIterator(); |
| } |
| public int size() { |
| return size; |
| } |
| public boolean contains(Object o) { |
| return containsValue(o); |
| } |
| public void clear() { |
| HashMap.this.clear(); |
| } |
| } |
| |
| /** |
| * Returns a {@link Set} view of the mappings contained in this map. |
| * The set is backed by the map, so changes to the map are |
| * reflected in the set, and vice-versa. If the map is modified |
| * while an iteration over the set is in progress (except through |
| * the iterator's own <tt>remove</tt> operation, or through the |
| * <tt>setValue</tt> operation on a map entry returned by the |
| * iterator) the results of the iteration are undefined. The set |
| * supports element removal, which removes the corresponding |
| * mapping from the map, via the <tt>Iterator.remove</tt>, |
| * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and |
| * <tt>clear</tt> operations. It does not support the |
| * <tt>add</tt> or <tt>addAll</tt> operations. |
| * |
| * @return a set view of the mappings contained in this map |
| */ |
| // Android-changed: Changed type parameter from <? extends Entry<K, V> |
| // to a Map.Entry<K, V>. |
| public Set<Map.Entry<K,V>> entrySet() { |
| return entrySet0(); |
| } |
| |
| private Set<Map.Entry<K,V>> entrySet0() { |
| Set<Map.Entry<K,V>> es = entrySet; |
| return es != null ? es : (entrySet = new EntrySet()); |
| } |
| |
| private final class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
| public Iterator<Map.Entry<K,V>> iterator() { |
| return newEntryIterator(); |
| } |
| public boolean contains(Object o) { |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry<K,V> e = (Map.Entry<K,V>) o; |
| Entry<K,V> candidate = getEntry(e.getKey()); |
| return candidate != null && candidate.equals(e); |
| } |
| public boolean remove(Object o) { |
| return removeMapping(o) != null; |
| } |
| public int size() { |
| return size; |
| } |
| public void clear() { |
| HashMap.this.clear(); |
| } |
| } |
| |
| /** |
| * Save the state of the <tt>HashMap</tt> instance to a stream (i.e., |
| * serialize it). |
| * |
| * @serialData The <i>capacity</i> of the HashMap (the length of the |
| * bucket array) is emitted (int), followed by the |
| * <i>size</i> (an int, the number of key-value |
| * mappings), followed by the key (Object) and value (Object) |
| * for each key-value mapping. The key-value mappings are |
| * emitted in no particular order. |
| */ |
| private void writeObject(java.io.ObjectOutputStream s) |
| throws IOException |
| { |
| // Write out the threshold, loadfactor, and any hidden stuff |
| s.defaultWriteObject(); |
| |
| // Write out number of buckets |
| if (table==EMPTY_TABLE) { |
| s.writeInt(roundUpToPowerOf2(threshold)); |
| } else { |
| s.writeInt(table.length); |
| } |
| |
| // Write out size (number of Mappings) |
| s.writeInt(size); |
| |
| // Write out keys and values (alternating) |
| if (size > 0) { |
| for(Map.Entry<K,V> e : entrySet0()) { |
| s.writeObject(e.getKey()); |
| s.writeObject(e.getValue()); |
| } |
| } |
| } |
| |
| private static final long serialVersionUID = 362498820763181265L; |
| |
| /** |
| * Reconstitute the {@code HashMap} instance from a stream (i.e., |
| * deserialize it). |
| */ |
| private void readObject(java.io.ObjectInputStream s) |
| throws IOException, ClassNotFoundException |
| { |
| // Read in the threshold (ignored), loadfactor, and any hidden stuff |
| s.defaultReadObject(); |
| if (loadFactor <= 0 || Float.isNaN(loadFactor)) { |
| throw new InvalidObjectException("Illegal load factor: " + |
| loadFactor); |
| } |
| |
| // set other fields that need values |
| table = (HashMapEntry<K,V>[]) EMPTY_TABLE; |
| |
| // Read in number of buckets |
| s.readInt(); // ignored. |
| |
| // Read number of mappings |
| int mappings = s.readInt(); |
| if (mappings < 0) |
| throw new InvalidObjectException("Illegal mappings count: " + |
| mappings); |
| |
| // capacity chosen by number of mappings and desired load (if >= 0.25) |
| int capacity = (int) Math.min( |
| mappings * Math.min(1 / loadFactor, 4.0f), |
| // we have limits... |
| HashMap.MAXIMUM_CAPACITY); |
| |
| // allocate the bucket array; |
| if (mappings > 0) { |
| inflateTable(capacity); |
| } else { |
| threshold = capacity; |
| } |
| |
| init(); // Give subclass a chance to do its thing. |
| |
| // Read the keys and values, and put the mappings in the HashMap |
| for (int i = 0; i < mappings; i++) { |
| K key = (K) s.readObject(); |
| V value = (V) s.readObject(); |
| putForCreate(key, value); |
| } |
| } |
| |
| // These methods are used when serializing HashSets |
| int capacity() { return table.length; } |
| float loadFactor() { return loadFactor; } |
| } |