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 javax.annotation.CheckForNull; 031import org.checkerframework.checker.nullness.qual.Nullable; 032 033/** 034 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and a {@code HashMap} 035 * instance for values-to-keys. Null keys are not permitted, but null values are. An {@code 036 * EnumHashBiMap} and its inverse are both serializable. 037 * 038 * <p>See the Guava User Guide article on <a href= 039 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap"> {@code BiMap}</a>. 040 * 041 * @author Mike Bostock 042 * @since 2.0 043 */ 044@GwtCompatible(emulated = true) 045@ElementTypesAreNonnullByDefault 046public final class EnumHashBiMap<K extends Enum<K>, V extends @Nullable Object> 047 extends AbstractBiMap<K, V> { 048 private transient Class<K> keyType; 049 050 /** 051 * Returns a new, empty {@code EnumHashBiMap} using the specified key type. 052 * 053 * @param keyType the key type 054 */ 055 public static <K extends Enum<K>, V extends @Nullable Object> EnumHashBiMap<K, V> create( 056 Class<K> keyType) { 057 return new EnumHashBiMap<>(keyType); 058 } 059 060 /** 061 * Constructs a new bimap with the same mappings as the specified map. If the specified map is an 062 * {@code EnumHashBiMap} or an {@link EnumBiMap}, the new bimap has the same key type as the input 063 * bimap. Otherwise, the specified map must contain at least one mapping, in order to determine 064 * the key type. 065 * 066 * @param map the map whose mappings are to be placed in this map 067 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an {@code EnumHashBiMap} 068 * instance and contains no mappings 069 */ 070 public static <K extends Enum<K>, V extends @Nullable Object> EnumHashBiMap<K, V> create( 071 Map<K, ? extends V> map) { 072 EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map)); 073 bimap.putAll(map); 074 return bimap; 075 } 076 077 private EnumHashBiMap(Class<K> keyType) { 078 super( 079 new EnumMap<K, V>(keyType), 080 Maps.<V, K>newHashMapWithExpectedSize(keyType.getEnumConstants().length)); 081 this.keyType = keyType; 082 } 083 084 // Overriding these 3 methods to show that values may be null (but not keys) 085 086 @Override 087 K checkKey(K key) { 088 return checkNotNull(key); 089 } 090 091 @CanIgnoreReturnValue 092 @Override 093 @SuppressWarnings("RedundantOverride") // b/192446478: RedundantOverride ignores some annotations. 094 // TODO(b/192446998): Remove this override after tools understand nullness better. 095 @CheckForNull 096 public V put(K key, @ParametricNullness V value) { 097 return super.put(key, value); 098 } 099 100 @CanIgnoreReturnValue 101 @Override 102 @SuppressWarnings("RedundantOverride") // b/192446478: RedundantOverride ignores some annotations. 103 // TODO(b/192446998): Remove this override after tools understand nullness better. 104 @CheckForNull 105 public V forcePut(K key, @ParametricNullness V value) { 106 return super.forcePut(key, value); 107 } 108 109 /** Returns the associated key type. */ 110 public Class<K> keyType() { 111 return keyType; 112 } 113 114 /** 115 * @serialData the key class, number of entries, first key, first value, second key, second value, 116 * and so on. 117 */ 118 @GwtIncompatible // java.io.ObjectOutputStream 119 private void writeObject(ObjectOutputStream stream) throws IOException { 120 stream.defaultWriteObject(); 121 stream.writeObject(keyType); 122 Serialization.writeMap(this, stream); 123 } 124 125 @SuppressWarnings("unchecked") // reading field populated by writeObject 126 @GwtIncompatible // java.io.ObjectInputStream 127 private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { 128 stream.defaultReadObject(); 129 keyType = (Class<K>) stream.readObject(); 130 setDelegates( 131 new EnumMap<K, V>(keyType), new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2)); 132 Serialization.populateMap(this, stream); 133 } 134 135 @GwtIncompatible // only needed in emulated source. 136 private static final long serialVersionUID = 0; 137}