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
017 package com.google.common.collect;
018
019 import com.google.common.annotations.GwtCompatible;
020 import com.google.common.annotations.GwtIncompatible;
021
022 import java.io.IOException;
023 import java.io.ObjectInputStream;
024 import java.io.ObjectOutputStream;
025 import java.util.EnumMap;
026 import java.util.HashMap;
027 import java.util.Map;
028
029 import javax.annotation.Nullable;
030
031 /**
032 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
033 * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
034 * but null values are. An {@code EnumHashBiMap} and its inverse are both
035 * serializable.
036 *
037 * @author Mike Bostock
038 * @since 2.0 (imported from Google Collections Library)
039 */
040 @GwtCompatible(emulated = true)
041 public final class EnumHashBiMap<K extends Enum<K>, V>
042 extends AbstractBiMap<K, V> {
043 private transient Class<K> keyType;
044
045 /**
046 * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
047 *
048 * @param keyType the key type
049 */
050 public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
051 create(Class<K> keyType) {
052 return new EnumHashBiMap<K, V>(keyType);
053 }
054
055 /**
056 * Constructs a new bimap with the same mappings as the specified map. If the
057 * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new
058 * bimap has the same key type as the input bimap. Otherwise, the specified
059 * map must contain at least one mapping, in order to determine the key type.
060 *
061 * @param map the map whose mappings are to be placed in this map
062 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an
063 * {@code EnumHashBiMap} instance and contains no mappings
064 */
065 public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
066 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(WellBehavedMap.wrap(
074 new EnumMap<K, V>(keyType)),
075 Maps.<V, K>newHashMapWithExpectedSize(
076 keyType.getEnumConstants().length));
077 this.keyType = keyType;
078 }
079
080 // Overriding these two methods to show that values may be null (but not keys)
081
082 @Override public V put(K key, @Nullable V value) {
083 return super.put(key, value);
084 }
085
086 @Override public V forcePut(K key, @Nullable V value) {
087 return super.forcePut(key, value);
088 }
089
090 /** Returns the associated key type. */
091 public Class<K> keyType() {
092 return keyType;
093 }
094
095 /**
096 * @serialData the key class, number of entries, first key, first value,
097 * second key, second value, and so on.
098 */
099 @GwtIncompatible("java.io.ObjectOutputStream")
100 private void writeObject(ObjectOutputStream stream) throws IOException {
101 stream.defaultWriteObject();
102 stream.writeObject(keyType);
103 Serialization.writeMap(this, stream);
104 }
105
106 @SuppressWarnings("unchecked") // reading field populated by writeObject
107 @GwtIncompatible("java.io.ObjectInputStream")
108 private void readObject(ObjectInputStream stream)
109 throws IOException, ClassNotFoundException {
110 stream.defaultReadObject();
111 keyType = (Class<K>) stream.readObject();
112 setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
113 new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
114 Serialization.populateMap(this, stream);
115 }
116
117 @GwtIncompatible("only needed in emulated source.")
118 private static final long serialVersionUID = 0;
119 }