001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import static com.google.common.base.Preconditions.checkNotNull; 020 021import com.google.common.annotations.GwtCompatible; 022import com.google.common.annotations.GwtIncompatible; 023import com.google.errorprone.annotations.CanIgnoreReturnValue; 024import java.io.IOException; 025import java.io.ObjectInputStream; 026import java.io.ObjectOutputStream; 027import java.util.EnumMap; 028import java.util.HashMap; 029import java.util.Map; 030import org.checkerframework.checker.nullness.qual.Nullable; 031 032/** 033 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and a {@code HashMap} 034 * instance for values-to-keys. Null keys are not permitted, but null values are. An {@code 035 * EnumHashBiMap} and its inverse are both serializable. 036 * 037 * <p>See the Guava User Guide article on <a href= 038 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap"> {@code BiMap}</a>. 039 * 040 * @author Mike Bostock 041 * @since 2.0 042 */ 043@GwtCompatible(emulated = true) 044public final class EnumHashBiMap<K extends Enum<K>, V> extends AbstractBiMap<K, V> { 045 private transient Class<K> keyType; 046 047 /** 048 * Returns a new, empty {@code EnumHashBiMap} using the specified key type. 049 * 050 * @param keyType the key type 051 */ 052 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> create(Class<K> keyType) { 053 return new EnumHashBiMap<>(keyType); 054 } 055 056 /** 057 * Constructs a new bimap with the same mappings as the specified map. If the specified map is an 058 * {@code EnumHashBiMap} or an {@link EnumBiMap}, the new bimap has the same key type as the input 059 * bimap. Otherwise, the specified map must contain at least one mapping, in order to determine 060 * the key type. 061 * 062 * @param map the map whose mappings are to be placed in this map 063 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an {@code EnumHashBiMap} 064 * instance and contains no mappings 065 */ 066 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> create(Map<K, ? extends V> map) { 067 EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map)); 068 bimap.putAll(map); 069 return bimap; 070 } 071 072 private EnumHashBiMap(Class<K> keyType) { 073 super( 074 new EnumMap<K, V>(keyType), 075 Maps.<V, K>newHashMapWithExpectedSize(keyType.getEnumConstants().length)); 076 this.keyType = keyType; 077 } 078 079 // Overriding these 3 methods to show that values may be null (but not keys) 080 081 @Override 082 K checkKey(K key) { 083 return checkNotNull(key); 084 } 085 086 @CanIgnoreReturnValue 087 @Override 088 public V put(K key, @Nullable V value) { 089 return super.put(key, value); 090 } 091 092 @CanIgnoreReturnValue 093 @Override 094 public V forcePut(K key, @Nullable V value) { 095 return super.forcePut(key, value); 096 } 097 098 /** Returns the associated key type. */ 099 public Class<K> keyType() { 100 return keyType; 101 } 102 103 /** 104 * @serialData the key class, number of entries, first key, first value, second key, second value, 105 * and so on. 106 */ 107 @GwtIncompatible // java.io.ObjectOutputStream 108 private void writeObject(ObjectOutputStream stream) throws IOException { 109 stream.defaultWriteObject(); 110 stream.writeObject(keyType); 111 Serialization.writeMap(this, stream); 112 } 113 114 @SuppressWarnings("unchecked") // reading field populated by writeObject 115 @GwtIncompatible // java.io.ObjectInputStream 116 private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { 117 stream.defaultReadObject(); 118 keyType = (Class<K>) stream.readObject(); 119 setDelegates( 120 new EnumMap<K, V>(keyType), new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2)); 121 Serialization.populateMap(this, stream); 122 } 123 124 @GwtIncompatible // only needed in emulated source. 125 private static final long serialVersionUID = 0; 126}