| /* |
| * Copyright 2003-2004 The Apache Software Foundation |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.collections.map; |
| |
| import java.io.IOException; |
| import java.io.ObjectInputStream; |
| import java.io.ObjectOutputStream; |
| import java.io.Serializable; |
| import java.util.Map; |
| |
| /** |
| * A <code>Map</code> implementation that matches keys and values based |
| * on <code>==</code> not <code>equals()</code>. |
| * <p> |
| * This map will violate the detail of various Map and map view contracts. |
| * As a general rule, don't compare this map to other maps. |
| * <p> |
| * <strong>Note that IdentityMap is not synchronized and is not thread-safe.</strong> |
| * If you wish to use this map from multiple threads concurrently, you must use |
| * appropriate synchronization. The simplest approach is to wrap this map |
| * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw |
| * exceptions when accessed by concurrent threads without synchronization. |
| * |
| * @since Commons Collections 3.0 |
| * @version $Revision: 1.1 $ $Date: 2009/05/27 22:16:30 $ |
| * |
| * @author java util HashMap |
| * @author Stephen Colebourne |
| */ |
| public class IdentityMap |
| extends AbstractHashedMap implements Serializable, Cloneable { |
| |
| /** Serialisation version */ |
| private static final long serialVersionUID = 2028493495224302329L; |
| |
| /** |
| * Constructs a new empty map with default size and load factor. |
| */ |
| public IdentityMap() { |
| super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD); |
| } |
| |
| /** |
| * Constructs a new, empty map with the specified initial capacity. |
| * |
| * @param initialCapacity the initial capacity |
| * @throws IllegalArgumentException if the initial capacity is less than one |
| */ |
| public IdentityMap(int initialCapacity) { |
| super(initialCapacity); |
| } |
| |
| /** |
| * Constructs a new, empty map 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 less than one |
| * @throws IllegalArgumentException if the load factor is less than zero |
| */ |
| public IdentityMap(int initialCapacity, float loadFactor) { |
| super(initialCapacity, loadFactor); |
| } |
| |
| /** |
| * Constructor copying elements from another map. |
| * |
| * @param map the map to copy |
| * @throws NullPointerException if the map is null |
| */ |
| public IdentityMap(Map map) { |
| super(map); |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Gets the hash code for the key specified. |
| * This implementation uses the identity hash code. |
| * |
| * @param key the key to get a hash code for |
| * @return the hash code |
| */ |
| protected int hash(Object key) { |
| return System.identityHashCode(key); |
| } |
| |
| /** |
| * Compares two keys for equals. |
| * This implementation uses <code>==</code>. |
| * |
| * @param key1 the first key to compare |
| * @param key2 the second key to compare |
| * @return true if equal by identity |
| */ |
| protected boolean isEqualKey(Object key1, Object key2) { |
| return (key1 == key2); |
| } |
| |
| /** |
| * Compares two values for equals. |
| * This implementation uses <code>==</code>. |
| * |
| * @param value1 the first value to compare |
| * @param value2 the second value to compare |
| * @return true if equal by identity |
| */ |
| protected boolean isEqualValue(Object value1, Object value2) { |
| return (value1 == value2); |
| } |
| |
| /** |
| * Creates an entry to store the data. |
| * This implementation creates an IdentityEntry instance. |
| * |
| * @param next the next entry in sequence |
| * @param hashCode the hash code to use |
| * @param key the key to store |
| * @param value the value to store |
| * @return the newly created entry |
| */ |
| protected HashEntry createEntry(HashEntry next, int hashCode, Object key, Object value) { |
| return new IdentityEntry(next, hashCode, key, value); |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * HashEntry |
| */ |
| protected static class IdentityEntry extends HashEntry { |
| |
| protected IdentityEntry(HashEntry next, int hashCode, Object key, Object value) { |
| super(next, hashCode, key, value); |
| } |
| |
| public boolean equals(Object obj) { |
| if (obj == this) { |
| return true; |
| } |
| if (obj instanceof Map.Entry == false) { |
| return false; |
| } |
| Map.Entry other = (Map.Entry) obj; |
| return |
| (getKey() == other.getKey()) && |
| (getValue() == other.getValue()); |
| } |
| |
| public int hashCode() { |
| return System.identityHashCode(getKey()) ^ |
| System.identityHashCode(getValue()); |
| } |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Clones the map without cloning the keys or values. |
| * |
| * @return a shallow clone |
| */ |
| public Object clone() { |
| return super.clone(); |
| } |
| |
| /** |
| * Write the map out using a custom routine. |
| */ |
| private void writeObject(ObjectOutputStream out) throws IOException { |
| out.defaultWriteObject(); |
| doWriteObject(out); |
| } |
| |
| /** |
| * Read the map in using a custom routine. |
| */ |
| private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { |
| in.defaultReadObject(); |
| doReadObject(in); |
| } |
| |
| } |