| /* |
| * Copyright (c) 2000, 2011, 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.*; |
| import java.util.function.BiConsumer; |
| import java.util.function.Consumer; |
| |
| /** |
| * This class implements the <tt>Map</tt> interface with a hash table, using |
| * reference-equality in place of object-equality when comparing keys (and |
| * values). In other words, in an <tt>IdentityHashMap</tt>, two keys |
| * <tt>k1</tt> and <tt>k2</tt> are considered equal if and only if |
| * <tt>(k1==k2)</tt>. (In normal <tt>Map</tt> implementations (like |
| * <tt>HashMap</tt>) two keys <tt>k1</tt> and <tt>k2</tt> are considered equal |
| * if and only if <tt>(k1==null ? k2==null : k1.equals(k2))</tt>.) |
| * |
| * <p><b>This class is <i>not</i> a general-purpose <tt>Map</tt> |
| * implementation! While this class implements the <tt>Map</tt> interface, it |
| * intentionally violates <tt>Map's</tt> general contract, which mandates the |
| * use of the <tt>equals</tt> method when comparing objects. This class is |
| * designed for use only in the rare cases wherein reference-equality |
| * semantics are required.</b> |
| * |
| * <p>A typical use of this class is <i>topology-preserving object graph |
| * transformations</i>, such as serialization or deep-copying. To perform such |
| * a transformation, a program must maintain a "node table" that keeps track |
| * of all the object references that have already been processed. The node |
| * table must not equate distinct objects even if they happen to be equal. |
| * Another typical use of this class is to maintain <i>proxy objects</i>. For |
| * example, a debugging facility might wish to maintain a proxy object for |
| * each object in the program being debugged. |
| * |
| * <p>This class provides all of the optional map operations, and permits |
| * <tt>null</tt> values and the <tt>null</tt> key. 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 class provides constant-time performance for the basic |
| * operations (<tt>get</tt> and <tt>put</tt>), assuming the system |
| * identity hash function ({@link System#identityHashCode(Object)}) |
| * disperses elements properly among the buckets. |
| * |
| * <p>This class has one tuning parameter (which affects performance but not |
| * semantics): <i>expected maximum size</i>. This parameter is the maximum |
| * number of key-value mappings that the map is expected to hold. Internally, |
| * this parameter is used to determine the number of buckets initially |
| * comprising the hash table. The precise relationship between the expected |
| * maximum size and the number of buckets is unspecified. |
| * |
| * <p>If the size of the map (the number of key-value mappings) sufficiently |
| * exceeds the expected maximum size, the number of buckets is increased |
| * Increasing the number of buckets ("rehashing") may be fairly expensive, so |
| * it pays to create identity hash maps with a sufficiently large expected |
| * maximum size. On the other hand, iteration over collection views requires |
| * time proportional to the number of buckets in the hash table, so it |
| * pays not to set the expected maximum size too high if you are especially |
| * concerned with iteration performance or memory usage. |
| * |
| * <p><strong>Note that this implementation is not synchronized.</strong> |
| * If multiple threads access an identity 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 IdentityHashMap(...));</pre> |
| * |
| * <p>The iterators returned by the <tt>iterator</tt> method of the |
| * collections 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>fail-fast iterators should be used only |
| * to detect bugs.</i> |
| * |
| * <p>Implementation note: This is a simple <i>linear-probe</i> hash table, |
| * as described for example in texts by Sedgewick and Knuth. The array |
| * alternates holding keys and values. (This has better locality for large |
| * tables than does using separate arrays.) For many JRE implementations |
| * and operation mixes, this class will yield better performance than |
| * {@link HashMap} (which uses <i>chaining</i> rather than linear-probing). |
| * |
| * <p>This class is a member of the |
| * <a href="{@docRoot}/../technotes/guides/collections/index.html"> |
| * Java Collections Framework</a>. |
| * |
| * @see System#identityHashCode(Object) |
| * @see Object#hashCode() |
| * @see Collection |
| * @see Map |
| * @see HashMap |
| * @see TreeMap |
| * @author Doug Lea and Josh Bloch |
| * @since 1.4 |
| */ |
| |
| public class IdentityHashMap<K,V> |
| extends AbstractMap<K,V> |
| implements Map<K,V>, java.io.Serializable, Cloneable |
| { |
| /** |
| * The initial capacity used by the no-args constructor. |
| * MUST be a power of two. The value 32 corresponds to the |
| * (specified) expected maximum size of 21, given a load factor |
| * of 2/3. |
| */ |
| private static final int DEFAULT_CAPACITY = 32; |
| |
| /** |
| * The minimum capacity, used if a lower value is implicitly specified |
| * by either of the constructors with arguments. The value 4 corresponds |
| * to an expected maximum size of 2, given a load factor of 2/3. |
| * MUST be a power of two. |
| */ |
| private static final int MINIMUM_CAPACITY = 4; |
| |
| /** |
| * 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<<29. |
| */ |
| private static final int MAXIMUM_CAPACITY = 1 << 29; |
| |
| /** |
| * The table, resized as necessary. Length MUST always be a power of two. |
| */ |
| private transient Object[] table; |
| |
| /** |
| * The number of key-value mappings contained in this identity hash map. |
| * |
| * @serial |
| */ |
| private int size; |
| |
| /** |
| * The number of modifications, to support fast-fail iterators |
| */ |
| private transient int modCount; |
| |
| /** |
| * The next size value at which to resize (capacity * load factor). |
| */ |
| private transient int threshold; |
| |
| /** |
| * Value representing null keys inside tables. |
| */ |
| private static final Object NULL_KEY = new Object(); |
| |
| /** |
| * Use NULL_KEY for key if it is null. |
| */ |
| private static Object maskNull(Object key) { |
| return (key == null ? NULL_KEY : key); |
| } |
| |
| /** |
| * Returns internal representation of null key back to caller as null. |
| */ |
| private static Object unmaskNull(Object key) { |
| return (key == NULL_KEY ? null : key); |
| } |
| |
| /** |
| * Constructs a new, empty identity hash map with a default expected |
| * maximum size (21). |
| */ |
| public IdentityHashMap() { |
| init(DEFAULT_CAPACITY); |
| } |
| |
| /** |
| * Constructs a new, empty map with the specified expected maximum size. |
| * Putting more than the expected number of key-value mappings into |
| * the map may cause the internal data structure to grow, which may be |
| * somewhat time-consuming. |
| * |
| * @param expectedMaxSize the expected maximum size of the map |
| * @throws IllegalArgumentException if <tt>expectedMaxSize</tt> is negative |
| */ |
| public IdentityHashMap(int expectedMaxSize) { |
| if (expectedMaxSize < 0) |
| throw new IllegalArgumentException("expectedMaxSize is negative: " |
| + expectedMaxSize); |
| init(capacity(expectedMaxSize)); |
| } |
| |
| /** |
| * Returns the appropriate capacity for the specified expected maximum |
| * size. Returns the smallest power of two between MINIMUM_CAPACITY |
| * and MAXIMUM_CAPACITY, inclusive, that is greater than |
| * (3 * expectedMaxSize)/2, if such a number exists. Otherwise |
| * returns MAXIMUM_CAPACITY. If (3 * expectedMaxSize)/2 is negative, it |
| * is assumed that overflow has occurred, and MAXIMUM_CAPACITY is returned. |
| */ |
| private int capacity(int expectedMaxSize) { |
| // Compute min capacity for expectedMaxSize given a load factor of 2/3 |
| int minCapacity = (3 * expectedMaxSize)/2; |
| |
| // Compute the appropriate capacity |
| int result; |
| if (minCapacity > MAXIMUM_CAPACITY || minCapacity < 0) { |
| result = MAXIMUM_CAPACITY; |
| } else { |
| result = MINIMUM_CAPACITY; |
| while (result < minCapacity) |
| result <<= 1; |
| } |
| return result; |
| } |
| |
| /** |
| * Initializes object to be an empty map with the specified initial |
| * capacity, which is assumed to be a power of two between |
| * MINIMUM_CAPACITY and MAXIMUM_CAPACITY inclusive. |
| */ |
| private void init(int initCapacity) { |
| // assert (initCapacity & -initCapacity) == initCapacity; // power of 2 |
| // assert initCapacity >= MINIMUM_CAPACITY; |
| // assert initCapacity <= MAXIMUM_CAPACITY; |
| |
| threshold = (initCapacity * 2)/3; |
| table = new Object[2 * initCapacity]; |
| } |
| |
| /** |
| * Constructs a new identity hash map containing the keys-value mappings |
| * in the specified map. |
| * |
| * @param m the map whose mappings are to be placed into this map |
| * @throws NullPointerException if the specified map is null |
| */ |
| public IdentityHashMap(Map<? extends K, ? extends V> m) { |
| // Allow for a bit of growth |
| this((int) ((1 + m.size()) * 1.1)); |
| putAll(m); |
| } |
| |
| /** |
| * Returns the number of key-value mappings in this identity hash map. |
| * |
| * @return the number of key-value mappings in this map |
| */ |
| public int size() { |
| return size; |
| } |
| |
| /** |
| * Returns <tt>true</tt> if this identity hash map contains no key-value |
| * mappings. |
| * |
| * @return <tt>true</tt> if this identity hash map contains no key-value |
| * mappings |
| */ |
| public boolean isEmpty() { |
| return size == 0; |
| } |
| |
| /** |
| * Returns index for Object x. |
| */ |
| private static int hash(Object x, int length) { |
| int h = System.identityHashCode(x); |
| // Multiply by -127, and left-shift to use least bit as part of hash |
| return ((h << 1) - (h << 8)) & (length - 1); |
| } |
| |
| /** |
| * Circularly traverses table of size len. |
| */ |
| private static int nextKeyIndex(int i, int len) { |
| return (i + 2 < len ? i + 2 : 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 == 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) { |
| Object k = maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| while (true) { |
| Object item = tab[i]; |
| if (item == k) |
| return (V) tab[i + 1]; |
| if (item == null) |
| return null; |
| i = nextKeyIndex(i, len); |
| } |
| } |
| |
| /** |
| * Tests whether the specified object reference is a key in this identity |
| * hash map. |
| * |
| * @param key possible key |
| * @return <code>true</code> if the specified object reference is a key |
| * in this map |
| * @see #containsValue(Object) |
| */ |
| public boolean containsKey(Object key) { |
| Object k = maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| while (true) { |
| Object item = tab[i]; |
| if (item == k) |
| return true; |
| if (item == null) |
| return false; |
| i = nextKeyIndex(i, len); |
| } |
| } |
| |
| /** |
| * Tests whether the specified object reference is a value in this identity |
| * hash map. |
| * |
| * @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 object reference |
| * @see #containsKey(Object) |
| */ |
| public boolean containsValue(Object value) { |
| Object[] tab = table; |
| for (int i = 1; i < tab.length; i += 2) |
| if (tab[i] == value && tab[i - 1] != null) |
| return true; |
| |
| return false; |
| } |
| |
| /** |
| * Tests if the specified key-value mapping is in the map. |
| * |
| * @param key possible key |
| * @param value possible value |
| * @return <code>true</code> if and only if the specified key-value |
| * mapping is in the map |
| */ |
| private boolean containsMapping(Object key, Object value) { |
| Object k = maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| while (true) { |
| Object item = tab[i]; |
| if (item == k) |
| return tab[i + 1] == value; |
| if (item == null) |
| return false; |
| i = nextKeyIndex(i, len); |
| } |
| } |
| |
| /** |
| * Associates the specified value with the specified key in this identity |
| * hash map. If the map previously contained a mapping for the key, the |
| * old value is replaced. |
| * |
| * @param key the key with which the specified value is to be associated |
| * @param value the 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>.) |
| * @see Object#equals(Object) |
| * @see #get(Object) |
| * @see #containsKey(Object) |
| */ |
| public V put(K key, V value) { |
| Object k = maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| |
| Object item; |
| while ( (item = tab[i]) != null) { |
| if (item == k) { |
| V oldValue = (V) tab[i + 1]; |
| tab[i + 1] = value; |
| return oldValue; |
| } |
| i = nextKeyIndex(i, len); |
| } |
| |
| modCount++; |
| tab[i] = k; |
| tab[i + 1] = value; |
| if (++size >= threshold) |
| resize(len); // len == 2 * current capacity. |
| return null; |
| } |
| |
| /** |
| * Resize the table to hold given capacity. |
| * |
| * @param newCapacity the new capacity, must be a power of two. |
| */ |
| private void resize(int newCapacity) { |
| // assert (newCapacity & -newCapacity) == newCapacity; // power of 2 |
| int newLength = newCapacity * 2; |
| |
| Object[] oldTable = table; |
| int oldLength = oldTable.length; |
| if (oldLength == 2*MAXIMUM_CAPACITY) { // can't expand any further |
| if (threshold == MAXIMUM_CAPACITY-1) |
| throw new IllegalStateException("Capacity exhausted."); |
| threshold = MAXIMUM_CAPACITY-1; // Gigantic map! |
| return; |
| } |
| if (oldLength >= newLength) |
| return; |
| |
| Object[] newTable = new Object[newLength]; |
| threshold = newLength / 3; |
| |
| for (int j = 0; j < oldLength; j += 2) { |
| Object key = oldTable[j]; |
| if (key != null) { |
| Object value = oldTable[j+1]; |
| oldTable[j] = null; |
| oldTable[j+1] = null; |
| int i = hash(key, newLength); |
| while (newTable[i] != null) |
| i = nextKeyIndex(i, newLength); |
| newTable[i] = key; |
| newTable[i + 1] = value; |
| } |
| } |
| table = newTable; |
| } |
| |
| /** |
| * 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 n = m.size(); |
| if (n == 0) |
| return; |
| if (n > threshold) // conservatively pre-expand |
| resize(capacity(n)); |
| |
| for (Entry<? extends K, ? extends V> e : m.entrySet()) |
| put(e.getKey(), e.getValue()); |
| } |
| |
| /** |
| * Removes the mapping for this 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) { |
| Object k = maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| |
| while (true) { |
| Object item = tab[i]; |
| if (item == k) { |
| modCount++; |
| size--; |
| V oldValue = (V) tab[i + 1]; |
| tab[i + 1] = null; |
| tab[i] = null; |
| closeDeletion(i); |
| return oldValue; |
| } |
| if (item == null) |
| return null; |
| i = nextKeyIndex(i, len); |
| } |
| |
| } |
| |
| /** |
| * Removes the specified key-value mapping from the map if it is present. |
| * |
| * @param key possible key |
| * @param value possible value |
| * @return <code>true</code> if and only if the specified key-value |
| * mapping was in the map |
| */ |
| private boolean removeMapping(Object key, Object value) { |
| Object k = maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| |
| while (true) { |
| Object item = tab[i]; |
| if (item == k) { |
| if (tab[i + 1] != value) |
| return false; |
| modCount++; |
| size--; |
| tab[i] = null; |
| tab[i + 1] = null; |
| closeDeletion(i); |
| return true; |
| } |
| if (item == null) |
| return false; |
| i = nextKeyIndex(i, len); |
| } |
| } |
| |
| /** |
| * Rehash all possibly-colliding entries following a |
| * deletion. This preserves the linear-probe |
| * collision properties required by get, put, etc. |
| * |
| * @param d the index of a newly empty deleted slot |
| */ |
| private void closeDeletion(int d) { |
| // Adapted from Knuth Section 6.4 Algorithm R |
| Object[] tab = table; |
| int len = tab.length; |
| |
| // Look for items to swap into newly vacated slot |
| // starting at index immediately following deletion, |
| // and continuing until a null slot is seen, indicating |
| // the end of a run of possibly-colliding keys. |
| Object item; |
| for (int i = nextKeyIndex(d, len); (item = tab[i]) != null; |
| i = nextKeyIndex(i, len) ) { |
| // The following test triggers if the item at slot i (which |
| // hashes to be at slot r) should take the spot vacated by d. |
| // If so, we swap it in, and then continue with d now at the |
| // newly vacated i. This process will terminate when we hit |
| // the null slot at the end of this run. |
| // The test is messy because we are using a circular table. |
| int r = hash(item, len); |
| if ((i < r && (r <= d || d <= i)) || (r <= d && d <= i)) { |
| tab[d] = item; |
| tab[d + 1] = tab[i + 1]; |
| tab[i] = null; |
| tab[i + 1] = null; |
| d = i; |
| } |
| } |
| } |
| |
| /** |
| * Removes all of the mappings from this map. |
| * The map will be empty after this call returns. |
| */ |
| public void clear() { |
| modCount++; |
| Object[] tab = table; |
| for (int i = 0; i < tab.length; i++) |
| tab[i] = null; |
| size = 0; |
| } |
| |
| /** |
| * Compares the specified object with this map for equality. Returns |
| * <tt>true</tt> if the given object is also a map and the two maps |
| * represent identical object-reference mappings. More formally, this |
| * map is equal to another map <tt>m</tt> if and only if |
| * <tt>this.entrySet().equals(m.entrySet())</tt>. |
| * |
| * <p><b>Owing to the reference-equality-based semantics of this map it is |
| * possible that the symmetry and transitivity requirements of the |
| * <tt>Object.equals</tt> contract may be violated if this map is compared |
| * to a normal map. However, the <tt>Object.equals</tt> contract is |
| * guaranteed to hold among <tt>IdentityHashMap</tt> instances.</b> |
| * |
| * @param o object to be compared for equality with this map |
| * @return <tt>true</tt> if the specified object is equal to this map |
| * @see Object#equals(Object) |
| */ |
| public boolean equals(Object o) { |
| if (o == this) { |
| return true; |
| } else if (o instanceof IdentityHashMap) { |
| IdentityHashMap m = (IdentityHashMap) o; |
| if (m.size() != size) |
| return false; |
| |
| Object[] tab = m.table; |
| for (int i = 0; i < tab.length; i+=2) { |
| Object k = tab[i]; |
| if (k != null && !containsMapping(k, tab[i + 1])) |
| return false; |
| } |
| return true; |
| } else if (o instanceof Map) { |
| Map m = (Map)o; |
| return entrySet().equals(m.entrySet()); |
| } else { |
| return false; // o is not a Map |
| } |
| } |
| |
| /** |
| * Returns the hash code value for this map. The hash code of a map is |
| * defined to be the sum of the hash codes of each entry in the map's |
| * <tt>entrySet()</tt> view. This ensures that <tt>m1.equals(m2)</tt> |
| * implies that <tt>m1.hashCode()==m2.hashCode()</tt> for any two |
| * <tt>IdentityHashMap</tt> instances <tt>m1</tt> and <tt>m2</tt>, as |
| * required by the general contract of {@link Object#hashCode}. |
| * |
| * <p><b>Owing to the reference-equality-based semantics of the |
| * <tt>Map.Entry</tt> instances in the set returned by this map's |
| * <tt>entrySet</tt> method, it is possible that the contractual |
| * requirement of <tt>Object.hashCode</tt> mentioned in the previous |
| * paragraph will be violated if one of the two objects being compared is |
| * an <tt>IdentityHashMap</tt> instance and the other is a normal map.</b> |
| * |
| * @return the hash code value for this map |
| * @see Object#equals(Object) |
| * @see #equals(Object) |
| */ |
| public int hashCode() { |
| int result = 0; |
| Object[] tab = table; |
| for (int i = 0; i < tab.length; i +=2) { |
| Object key = tab[i]; |
| if (key != null) { |
| Object k = unmaskNull(key); |
| result += System.identityHashCode(k) ^ |
| System.identityHashCode(tab[i + 1]); |
| } |
| } |
| return result; |
| } |
| |
| /** |
| * Returns a shallow copy of this identity hash map: the keys and values |
| * themselves are not cloned. |
| * |
| * @return a shallow copy of this map |
| */ |
| public Object clone() { |
| try { |
| IdentityHashMap<K,V> m = (IdentityHashMap<K,V>) super.clone(); |
| m.entrySet = null; |
| m.table = table.clone(); |
| return m; |
| } catch (CloneNotSupportedException e) { |
| throw new InternalError(); |
| } |
| } |
| |
| private abstract class IdentityHashMapIterator<T> implements Iterator<T> { |
| int index = (size != 0 ? 0 : table.length); // current slot. |
| int expectedModCount = modCount; // to support fast-fail |
| int lastReturnedIndex = -1; // to allow remove() |
| boolean indexValid; // To avoid unnecessary next computation |
| Object[] traversalTable = table; // reference to main table or copy |
| |
| public boolean hasNext() { |
| Object[] tab = traversalTable; |
| for (int i = index; i < tab.length; i+=2) { |
| Object key = tab[i]; |
| if (key != null) { |
| index = i; |
| return indexValid = true; |
| } |
| } |
| index = tab.length; |
| return false; |
| } |
| |
| protected int nextIndex() { |
| if (modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| if (!indexValid && !hasNext()) |
| throw new NoSuchElementException(); |
| |
| indexValid = false; |
| lastReturnedIndex = index; |
| index += 2; |
| return lastReturnedIndex; |
| } |
| |
| public void remove() { |
| if (lastReturnedIndex == -1) |
| throw new IllegalStateException(); |
| if (modCount != expectedModCount) |
| throw new ConcurrentModificationException(); |
| |
| expectedModCount = ++modCount; |
| int deletedSlot = lastReturnedIndex; |
| lastReturnedIndex = -1; |
| // back up index to revisit new contents after deletion |
| index = deletedSlot; |
| indexValid = false; |
| |
| // Removal code proceeds as in closeDeletion except that |
| // it must catch the rare case where an element already |
| // seen is swapped into a vacant slot that will be later |
| // traversed by this iterator. We cannot allow future |
| // next() calls to return it again. The likelihood of |
| // this occurring under 2/3 load factor is very slim, but |
| // when it does happen, we must make a copy of the rest of |
| // the table to use for the rest of the traversal. Since |
| // this can only happen when we are near the end of the table, |
| // even in these rare cases, this is not very expensive in |
| // time or space. |
| |
| Object[] tab = traversalTable; |
| int len = tab.length; |
| |
| int d = deletedSlot; |
| K key = (K) tab[d]; |
| tab[d] = null; // vacate the slot |
| tab[d + 1] = null; |
| |
| // If traversing a copy, remove in real table. |
| // We can skip gap-closure on copy. |
| if (tab != IdentityHashMap.this.table) { |
| IdentityHashMap.this.remove(key); |
| expectedModCount = modCount; |
| return; |
| } |
| |
| size--; |
| |
| Object item; |
| for (int i = nextKeyIndex(d, len); (item = tab[i]) != null; |
| i = nextKeyIndex(i, len)) { |
| int r = hash(item, len); |
| // See closeDeletion for explanation of this conditional |
| if ((i < r && (r <= d || d <= i)) || |
| (r <= d && d <= i)) { |
| |
| // If we are about to swap an already-seen element |
| // into a slot that may later be returned by next(), |
| // then clone the rest of table for use in future |
| // next() calls. It is OK that our copy will have |
| // a gap in the "wrong" place, since it will never |
| // be used for searching anyway. |
| |
| if (i < deletedSlot && d >= deletedSlot && |
| traversalTable == IdentityHashMap.this.table) { |
| int remaining = len - deletedSlot; |
| Object[] newTable = new Object[remaining]; |
| System.arraycopy(tab, deletedSlot, |
| newTable, 0, remaining); |
| traversalTable = newTable; |
| index = 0; |
| } |
| |
| tab[d] = item; |
| tab[d + 1] = tab[i + 1]; |
| tab[i] = null; |
| tab[i + 1] = null; |
| d = i; |
| } |
| } |
| } |
| } |
| |
| private class KeyIterator extends IdentityHashMapIterator<K> { |
| public K next() { |
| return (K) unmaskNull(traversalTable[nextIndex()]); |
| } |
| } |
| |
| private class ValueIterator extends IdentityHashMapIterator<V> { |
| public V next() { |
| return (V) traversalTable[nextIndex() + 1]; |
| } |
| } |
| |
| private class EntryIterator |
| extends IdentityHashMapIterator<Map.Entry<K,V>> |
| { |
| private Entry lastReturnedEntry = null; |
| |
| public Map.Entry<K,V> next() { |
| lastReturnedEntry = new Entry(nextIndex()); |
| return lastReturnedEntry; |
| } |
| |
| public void remove() { |
| lastReturnedIndex = |
| ((null == lastReturnedEntry) ? -1 : lastReturnedEntry.index); |
| super.remove(); |
| lastReturnedEntry.index = lastReturnedIndex; |
| lastReturnedEntry = null; |
| } |
| |
| private class Entry implements Map.Entry<K,V> { |
| private int index; |
| |
| private Entry(int index) { |
| this.index = index; |
| } |
| |
| public K getKey() { |
| checkIndexForEntryUse(); |
| return (K) unmaskNull(traversalTable[index]); |
| } |
| |
| public V getValue() { |
| checkIndexForEntryUse(); |
| return (V) traversalTable[index+1]; |
| } |
| |
| public V setValue(V value) { |
| checkIndexForEntryUse(); |
| V oldValue = (V) traversalTable[index+1]; |
| traversalTable[index+1] = value; |
| // if shadowing, force into main table |
| if (traversalTable != IdentityHashMap.this.table) |
| put((K) traversalTable[index], value); |
| return oldValue; |
| } |
| |
| public boolean equals(Object o) { |
| if (index < 0) |
| return super.equals(o); |
| |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry e = (Map.Entry)o; |
| return (e.getKey() == unmaskNull(traversalTable[index]) && |
| e.getValue() == traversalTable[index+1]); |
| } |
| |
| public int hashCode() { |
| if (lastReturnedIndex < 0) |
| return super.hashCode(); |
| |
| return (System.identityHashCode(unmaskNull(traversalTable[index])) ^ |
| System.identityHashCode(traversalTable[index+1])); |
| } |
| |
| public String toString() { |
| if (index < 0) |
| return super.toString(); |
| |
| return (unmaskNull(traversalTable[index]) + "=" |
| + traversalTable[index+1]); |
| } |
| |
| private void checkIndexForEntryUse() { |
| if (index < 0) |
| throw new IllegalStateException("Entry was removed"); |
| } |
| } |
| } |
| |
| // Views |
| |
| /** |
| * This field is initialized to contain an instance of the entry set |
| * view the first time this view is requested. The view is stateless, |
| * so there's no reason to create more than one. |
| */ |
| private transient Set<Map.Entry<K,V>> entrySet = null; |
| |
| /** |
| * Returns an identity-based 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, 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> methods. It does not support the <tt>add</tt> or |
| * <tt>addAll</tt> methods. |
| * |
| * <p><b>While the object returned by this method implements the |
| * <tt>Set</tt> interface, it does <i>not</i> obey <tt>Set's</tt> general |
| * contract. Like its backing map, the set returned by this method |
| * defines element equality as reference-equality rather than |
| * object-equality. This affects the behavior of its <tt>contains</tt>, |
| * <tt>remove</tt>, <tt>containsAll</tt>, <tt>equals</tt>, and |
| * <tt>hashCode</tt> methods.</b> |
| * |
| * <p><b>The <tt>equals</tt> method of the returned set returns <tt>true</tt> |
| * only if the specified object is a set containing exactly the same |
| * object references as the returned set. The symmetry and transitivity |
| * requirements of the <tt>Object.equals</tt> contract may be violated if |
| * the set returned by this method is compared to a normal set. However, |
| * the <tt>Object.equals</tt> contract is guaranteed to hold among sets |
| * returned by this method.</b> |
| * |
| * <p>The <tt>hashCode</tt> method of the returned set returns the sum of |
| * the <i>identity hashcodes</i> of the elements in the set, rather than |
| * the sum of their hashcodes. This is mandated by the change in the |
| * semantics of the <tt>equals</tt> method, in order to enforce the |
| * general contract of the <tt>Object.hashCode</tt> method among sets |
| * returned by this method. |
| * |
| * @return an identity-based set view of the keys contained in this map |
| * @see Object#equals(Object) |
| * @see System#identityHashCode(Object) |
| */ |
| public Set<K> keySet() { |
| Set<K> ks = keySet; |
| if (ks != null) |
| return ks; |
| else |
| return keySet = new KeySet(); |
| } |
| |
| private class KeySet extends AbstractSet<K> { |
| public Iterator<K> iterator() { |
| return new KeyIterator(); |
| } |
| public int size() { |
| return size; |
| } |
| public boolean contains(Object o) { |
| return containsKey(o); |
| } |
| public boolean remove(Object o) { |
| int oldSize = size; |
| IdentityHashMap.this.remove(o); |
| return size != oldSize; |
| } |
| /* |
| * Must revert from AbstractSet's impl to AbstractCollection's, as |
| * the former contains an optimization that results in incorrect |
| * behavior when c is a smaller "normal" (non-identity-based) Set. |
| */ |
| public boolean removeAll(Collection<?> c) { |
| boolean modified = false; |
| for (Iterator<K> i = iterator(); i.hasNext(); ) { |
| if (c.contains(i.next())) { |
| i.remove(); |
| modified = true; |
| } |
| } |
| return modified; |
| } |
| public void clear() { |
| IdentityHashMap.this.clear(); |
| } |
| public int hashCode() { |
| int result = 0; |
| for (K key : this) |
| result += System.identityHashCode(key); |
| return result; |
| } |
| } |
| |
| /** |
| * 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, |
| * 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> methods. It does not |
| * support the <tt>add</tt> or <tt>addAll</tt> methods. |
| * |
| * <p><b>While the object returned by this method implements the |
| * <tt>Collection</tt> interface, it does <i>not</i> obey |
| * <tt>Collection's</tt> general contract. Like its backing map, |
| * the collection returned by this method defines element equality as |
| * reference-equality rather than object-equality. This affects the |
| * behavior of its <tt>contains</tt>, <tt>remove</tt> and |
| * <tt>containsAll</tt> methods.</b> |
| */ |
| public Collection<V> values() { |
| Collection<V> vs = values; |
| if (vs != null) |
| return vs; |
| else |
| return values = new Values(); |
| } |
| |
| private class Values extends AbstractCollection<V> { |
| public Iterator<V> iterator() { |
| return new ValueIterator(); |
| } |
| public int size() { |
| return size; |
| } |
| public boolean contains(Object o) { |
| return containsValue(o); |
| } |
| public boolean remove(Object o) { |
| for (Iterator<V> i = iterator(); i.hasNext(); ) { |
| if (i.next() == o) { |
| i.remove(); |
| return true; |
| } |
| } |
| return false; |
| } |
| public void clear() { |
| IdentityHashMap.this.clear(); |
| } |
| } |
| |
| /** |
| * Returns a {@link Set} view of the mappings contained in this map. |
| * Each element in the returned set is a reference-equality-based |
| * <tt>Map.Entry</tt>. 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, |
| * 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> |
| * methods. It does not support the <tt>add</tt> or |
| * <tt>addAll</tt> methods. |
| * |
| * <p>Like the backing map, the <tt>Map.Entry</tt> objects in the set |
| * returned by this method define key and value equality as |
| * reference-equality rather than object-equality. This affects the |
| * behavior of the <tt>equals</tt> and <tt>hashCode</tt> methods of these |
| * <tt>Map.Entry</tt> objects. A reference-equality based <tt>Map.Entry |
| * e</tt> is equal to an object <tt>o</tt> if and only if <tt>o</tt> is a |
| * <tt>Map.Entry</tt> and <tt>e.getKey()==o.getKey() && |
| * e.getValue()==o.getValue()</tt>. To accommodate these equals |
| * semantics, the <tt>hashCode</tt> method returns |
| * <tt>System.identityHashCode(e.getKey()) ^ |
| * System.identityHashCode(e.getValue())</tt>. |
| * |
| * <p><b>Owing to the reference-equality-based semantics of the |
| * <tt>Map.Entry</tt> instances in the set returned by this method, |
| * it is possible that the symmetry and transitivity requirements of |
| * the {@link Object#equals(Object)} contract may be violated if any of |
| * the entries in the set is compared to a normal map entry, or if |
| * the set returned by this method is compared to a set of normal map |
| * entries (such as would be returned by a call to this method on a normal |
| * map). However, the <tt>Object.equals</tt> contract is guaranteed to |
| * hold among identity-based map entries, and among sets of such entries. |
| * </b> |
| * |
| * @return a set view of the identity-mappings contained in this map |
| */ |
| public Set<Map.Entry<K,V>> entrySet() { |
| Set<Map.Entry<K,V>> es = entrySet; |
| if (es != null) |
| return es; |
| else |
| return entrySet = new EntrySet(); |
| } |
| |
| private class EntrySet extends AbstractSet<Map.Entry<K,V>> { |
| public Iterator<Map.Entry<K,V>> iterator() { |
| return new EntryIterator(); |
| } |
| public boolean contains(Object o) { |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry entry = (Map.Entry)o; |
| return containsMapping(entry.getKey(), entry.getValue()); |
| } |
| public boolean remove(Object o) { |
| if (!(o instanceof Map.Entry)) |
| return false; |
| Map.Entry entry = (Map.Entry)o; |
| return removeMapping(entry.getKey(), entry.getValue()); |
| } |
| public int size() { |
| return size; |
| } |
| public void clear() { |
| IdentityHashMap.this.clear(); |
| } |
| /* |
| * Must revert from AbstractSet's impl to AbstractCollection's, as |
| * the former contains an optimization that results in incorrect |
| * behavior when c is a smaller "normal" (non-identity-based) Set. |
| */ |
| public boolean removeAll(Collection<?> c) { |
| boolean modified = false; |
| for (Iterator<Map.Entry<K,V>> i = iterator(); i.hasNext(); ) { |
| if (c.contains(i.next())) { |
| i.remove(); |
| modified = true; |
| } |
| } |
| return modified; |
| } |
| |
| public Object[] toArray() { |
| int size = size(); |
| Object[] result = new Object[size]; |
| Iterator<Map.Entry<K,V>> it = iterator(); |
| for (int i = 0; i < size; i++) |
| result[i] = new AbstractMap.SimpleEntry<>(it.next()); |
| return result; |
| } |
| |
| @SuppressWarnings("unchecked") |
| public <T> T[] toArray(T[] a) { |
| int size = size(); |
| if (a.length < size) |
| a = (T[])java.lang.reflect.Array |
| .newInstance(a.getClass().getComponentType(), size); |
| Iterator<Map.Entry<K,V>> it = iterator(); |
| for (int i = 0; i < size; i++) |
| a[i] = (T) new AbstractMap.SimpleEntry<>(it.next()); |
| if (a.length > size) |
| a[size] = null; |
| return a; |
| } |
| } |
| |
| |
| private static final long serialVersionUID = 8188218128353913216L; |
| |
| /** |
| * Save the state of the <tt>IdentityHashMap</tt> instance to a stream |
| * (i.e., serialize it). |
| * |
| * @serialData The <i>size</i> of the HashMap (the number of key-value |
| * mappings) (<tt>int</tt>), followed by the key (Object) and |
| * value (Object) for each key-value mapping represented by the |
| * IdentityHashMap. The key-value mappings are emitted in no |
| * particular order. |
| */ |
| private void writeObject(java.io.ObjectOutputStream s) |
| throws java.io.IOException { |
| // Write out and any hidden stuff |
| s.defaultWriteObject(); |
| |
| // Write out size (number of Mappings) |
| s.writeInt(size); |
| |
| // Write out keys and values (alternating) |
| Object[] tab = table; |
| for (int i = 0; i < tab.length; i += 2) { |
| Object key = tab[i]; |
| if (key != null) { |
| s.writeObject(unmaskNull(key)); |
| s.writeObject(tab[i + 1]); |
| } |
| } |
| } |
| |
| /** |
| * Reconstitute the <tt>IdentityHashMap</tt> instance from a stream (i.e., |
| * deserialize it). |
| */ |
| private void readObject(java.io.ObjectInputStream s) |
| throws java.io.IOException, ClassNotFoundException { |
| // Read in any hidden stuff |
| s.defaultReadObject(); |
| |
| // Read in size (number of Mappings) |
| int size = s.readInt(); |
| |
| // Allow for 33% growth (i.e., capacity is >= 2* size()). |
| init(capacity((size*4)/3)); |
| |
| // Read the keys and values, and put the mappings in the table |
| for (int i=0; i<size; i++) { |
| K key = (K) s.readObject(); |
| V value = (V) s.readObject(); |
| putForCreate(key, value); |
| } |
| } |
| |
| /** |
| * The put method for readObject. It does not resize the table, |
| * update modCount, etc. |
| */ |
| private void putForCreate(K key, V value) |
| throws IOException |
| { |
| K k = (K)maskNull(key); |
| Object[] tab = table; |
| int len = tab.length; |
| int i = hash(k, len); |
| |
| Object item; |
| while ( (item = tab[i]) != null) { |
| if (item == k) |
| throw new java.io.StreamCorruptedException(); |
| i = nextKeyIndex(i, len); |
| } |
| tab[i] = k; |
| tab[i + 1] = value; |
| } |
| |
| @SuppressWarnings("unchecked") |
| @Override |
| public void forEach(BiConsumer<? super K, ? super V> action) { |
| Objects.requireNonNull(action); |
| int expectedModCount = modCount; |
| |
| Object[] t = table; |
| for (int index = 0; index < t.length; index += 2) { |
| Object k = t[index]; |
| if (k != null) { |
| action.accept((K) unmaskNull(k), (V) t[index + 1]); |
| } |
| |
| if (modCount != expectedModCount) { |
| throw new ConcurrentModificationException(); |
| } |
| } |
| } |
| |
| } |
