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 */ 017package org.apache.commons.collections4.bidimap; 018 019import java.io.IOException; 020import java.io.ObjectInputStream; 021import java.io.ObjectOutputStream; 022import java.io.Serializable; 023import java.util.LinkedHashMap; 024import java.util.Map; 025 026import org.apache.commons.collections4.BidiMap; 027 028/** 029 * Implements {@link BidiMap} with two {@link LinkedHashMap} instances. 030 * <p> 031 * Two {@link LinkedHashMap} instances are used in this class. 032 * This provides fast lookups at the expense of storing two sets of map entries and two linked lists. 033 * </p> 034 * 035 * @param <K> the type of the keys in the map 036 * @param <V> the type of the values in the map 037 * 038 * @since 4.0 039 */ 040public class DualLinkedHashBidiMap<K, V> extends AbstractDualBidiMap<K, V> implements Serializable { 041 042 /** Ensure serialization compatibility */ 043 private static final long serialVersionUID = 721969328361810L; 044 045 /** 046 * Creates an empty {@code HashBidiMap}. 047 */ 048 public DualLinkedHashBidiMap() { 049 super(new LinkedHashMap<>(), new LinkedHashMap<>()); 050 } 051 052 /** 053 * Constructs a {@code LinkedHashBidiMap} and copies the mappings from 054 * specified {@link Map}. 055 * 056 * @param map the map whose mappings are to be placed in this map 057 */ 058 public DualLinkedHashBidiMap(final Map<? extends K, ? extends V> map) { 059 super(new LinkedHashMap<>(), new LinkedHashMap<>()); 060 putAll(map); 061 } 062 063 /** 064 * Constructs a {@code LinkedHashBidiMap} that decorates the specified maps. 065 * 066 * @param normalMap the normal direction map 067 * @param reverseMap the reverse direction map 068 * @param inverseBidiMap the inverse BidiMap 069 */ 070 protected DualLinkedHashBidiMap(final Map<K, V> normalMap, final Map<V, K> reverseMap, 071 final BidiMap<V, K> inverseBidiMap) { 072 super(normalMap, reverseMap, inverseBidiMap); 073 } 074 075 /** 076 * Creates a new instance of this object. 077 * 078 * @param normalMap the normal direction map 079 * @param reverseMap the reverse direction map 080 * @param inverseBidiMap the inverse BidiMap 081 * @return new bidi map 082 */ 083 @Override 084 protected BidiMap<V, K> createBidiMap(final Map<V, K> normalMap, final Map<K, V> reverseMap, 085 final BidiMap<K, V> inverseBidiMap) { 086 return new DualLinkedHashBidiMap<>(normalMap, reverseMap, inverseBidiMap); 087 } 088 089 private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException { 090 in.defaultReadObject(); 091 normalMap = new LinkedHashMap<>(); 092 reverseMap = new LinkedHashMap<>(); 093 @SuppressWarnings("unchecked") // will fail at runtime if stream is incorrect 094 final Map<K, V> map = (Map<K, V>) in.readObject(); 095 putAll(map); 096 } 097 098 // Serialization 099 private void writeObject(final ObjectOutputStream out) throws IOException { 100 out.defaultWriteObject(); 101 out.writeObject(normalMap); 102 } 103}