001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.bidimap; 018 019 import java.io.IOException; 020 import java.io.ObjectInputStream; 021 import java.io.ObjectOutputStream; 022 import java.io.Serializable; 023 import java.util.HashMap; 024 import java.util.Map; 025 026 import org.apache.commons.collections.BidiMap; 027 028 /** 029 * Implementation of <code>BidiMap</code> that uses two <code>HashMap</code> instances. 030 * <p> 031 * Two <code>HashMap</code> instances are used in this class. 032 * This provides fast lookups at the expense of storing two sets of map entries. 033 * Commons Collections would welcome the addition of a direct hash-based 034 * implementation of the <code>BidiMap</code> interface. 035 * <p> 036 * NOTE: From Commons Collections 3.1, all subclasses will use <code>HashMap</code> 037 * and the flawed <code>createMap</code> method is ignored. 038 * 039 * @since Commons Collections 3.0 040 * @version $Id: DualHashBidiMap.java 646777 2008-04-10 12:33:15Z niallp $ 041 * 042 * @author Matthew Hawthorne 043 * @author Stephen Colebourne 044 */ 045 public class DualHashBidiMap 046 extends AbstractDualBidiMap implements Serializable { 047 048 /** Ensure serialization compatibility */ 049 private static final long serialVersionUID = 721969328361808L; 050 051 /** 052 * Creates an empty <code>HashBidiMap</code>. 053 */ 054 public DualHashBidiMap() { 055 super(new HashMap(), new HashMap()); 056 } 057 058 /** 059 * Constructs a <code>HashBidiMap</code> and copies the mappings from 060 * specified <code>Map</code>. 061 * 062 * @param map the map whose mappings are to be placed in this map 063 */ 064 public DualHashBidiMap(Map map) { 065 super(new HashMap(), new HashMap()); 066 putAll(map); 067 } 068 069 /** 070 * Constructs a <code>HashBidiMap</code> that decorates the specified maps. 071 * 072 * @param normalMap the normal direction map 073 * @param reverseMap the reverse direction map 074 * @param inverseBidiMap the inverse BidiMap 075 */ 076 protected DualHashBidiMap(Map normalMap, Map reverseMap, BidiMap inverseBidiMap) { 077 super(normalMap, reverseMap, inverseBidiMap); 078 } 079 080 /** 081 * Creates a new instance of this object. 082 * 083 * @param normalMap the normal direction map 084 * @param reverseMap the reverse direction map 085 * @param inverseBidiMap the inverse BidiMap 086 * @return new bidi map 087 */ 088 protected BidiMap createBidiMap(Map normalMap, Map reverseMap, BidiMap inverseBidiMap) { 089 return new DualHashBidiMap(normalMap, reverseMap, inverseBidiMap); 090 } 091 092 // Serialization 093 //----------------------------------------------------------------------- 094 private void writeObject(ObjectOutputStream out) throws IOException { 095 out.defaultWriteObject(); 096 out.writeObject(maps[0]); 097 } 098 099 private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { 100 in.defaultReadObject(); 101 maps[0] = new HashMap(); 102 maps[1] = new HashMap(); 103 Map map = (Map) in.readObject(); 104 putAll(map); 105 } 106 107 }