HashBiMap.java revision 1d580d0f6ee4f21eb309ba7b509d2c6d671c4044
1/* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.google.common.collect; 18 19import com.google.common.annotations.GwtCompatible; 20import com.google.common.annotations.GwtIncompatible; 21 22import java.io.IOException; 23import java.io.ObjectInputStream; 24import java.io.ObjectOutputStream; 25import java.util.HashMap; 26import java.util.Map; 27 28import javax.annotation.Nullable; 29 30/** 31 * A {@link BiMap} backed by two {@link HashMap} instances. This implementation 32 * allows null keys and values. A {@code HashBiMap} and its inverse are both 33 * serializable. 34 * 35 * @author Mike Bostock 36 * @since 2.0 (imported from Google Collections Library) 37 */ 38@GwtCompatible(emulated = true) 39public final class HashBiMap<K, V> extends AbstractBiMap<K, V> { 40 41 /** 42 * Returns a new, empty {@code HashBiMap} with the default initial capacity 43 * (16). 44 */ 45 public static <K, V> HashBiMap<K, V> create() { 46 return new HashBiMap<K, V>(); 47 } 48 49 /** 50 * Constructs a new, empty bimap with the specified expected size. 51 * 52 * @param expectedSize the expected number of entries 53 * @throws IllegalArgumentException if the specified expected size is 54 * negative 55 */ 56 public static <K, V> HashBiMap<K, V> create(int expectedSize) { 57 return new HashBiMap<K, V>(expectedSize); 58 } 59 60 /** 61 * Constructs a new bimap containing initial values from {@code map}. The 62 * bimap is created with an initial capacity sufficient to hold the mappings 63 * in the specified map. 64 */ 65 public static <K, V> HashBiMap<K, V> create( 66 Map<? extends K, ? extends V> map) { 67 HashBiMap<K, V> bimap = create(map.size()); 68 bimap.putAll(map); 69 return bimap; 70 } 71 72 private HashBiMap() { 73 super(new HashMap<K, V>(), new HashMap<V, K>()); 74 } 75 76 private HashBiMap(int expectedSize) { 77 super( 78 Maps.<K, V>newHashMapWithExpectedSize(expectedSize), 79 Maps.<V, K>newHashMapWithExpectedSize(expectedSize)); 80 } 81 82 // Override these two methods to show that keys and values may be null 83 84 @Override public V put(@Nullable K key, @Nullable V value) { 85 return super.put(key, value); 86 } 87 88 @Override public V forcePut(@Nullable K key, @Nullable V value) { 89 return super.forcePut(key, value); 90 } 91 92 /** 93 * @serialData the number of entries, first key, first value, second key, 94 * second value, and so on. 95 */ 96 @GwtIncompatible("java.io.ObjectOutputStream") 97 private void writeObject(ObjectOutputStream stream) throws IOException { 98 stream.defaultWriteObject(); 99 Serialization.writeMap(this, stream); 100 } 101 102 @GwtIncompatible("java.io.ObjectInputStream") 103 private void readObject(ObjectInputStream stream) 104 throws IOException, ClassNotFoundException { 105 stream.defaultReadObject(); 106 int size = Serialization.readCount(stream); 107 setDelegates(Maps.<K, V>newHashMapWithExpectedSize(size), 108 Maps.<V, K>newHashMapWithExpectedSize(size)); 109 Serialization.populateMap(this, stream, size); 110 } 111 112 @GwtIncompatible("Not needed in emulated source") 113 private static final long serialVersionUID = 0; 114} 115