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 static com.google.common.base.Preconditions.checkNotNull;
020
021 import com.google.common.annotations.GwtCompatible;
022 import com.google.common.annotations.GwtIncompatible;
023
024 import java.io.IOException;
025 import java.io.ObjectInputStream;
026 import java.io.ObjectOutputStream;
027 import java.util.EnumMap;
028 import java.util.HashMap;
029 import java.util.Map;
030
031 import javax.annotation.Nullable;
032
033 /**
034 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
035 * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
036 * but null values are. An {@code EnumHashBiMap} and its inverse are both
037 * serializable.
038 *
039 * <p>See the Guava User Guide article on <a href=
040 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
041 * {@code BiMap}</a>.
042 *
043 * @author Mike Bostock
044 * @since 2.0 (imported from Google Collections Library)
045 */
046 @GwtCompatible(emulated = true)
047 public final class EnumHashBiMap<K extends Enum<K>, V>
048 extends AbstractBiMap<K, V> {
049 private transient Class<K> keyType;
050
051 /**
052 * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
053 *
054 * @param keyType the key type
055 */
056 public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
057 create(Class<K> keyType) {
058 return new EnumHashBiMap<K, V>(keyType);
059 }
060
061 /**
062 * Constructs a new bimap with the same mappings as the specified map. If the
063 * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new
064 * bimap has the same key type as the input bimap. Otherwise, the specified
065 * map must contain at least one mapping, in order to determine the key type.
066 *
067 * @param map the map whose mappings are to be placed in this map
068 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an
069 * {@code EnumHashBiMap} instance and contains no mappings
070 */
071 public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
072 create(Map<K, ? extends V> map) {
073 EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
074 bimap.putAll(map);
075 return bimap;
076 }
077
078 private EnumHashBiMap(Class<K> keyType) {
079 super(WellBehavedMap.wrap(
080 new EnumMap<K, V>(keyType)),
081 Maps.<V, K>newHashMapWithExpectedSize(
082 keyType.getEnumConstants().length));
083 this.keyType = keyType;
084 }
085
086 // Overriding these three methods to show that values may be null (but not keys)
087
088 @Override
089 K checkKey(K key) {
090 return checkNotNull(key);
091 }
092
093 @Override public V put(K key, @Nullable V value) {
094 return super.put(key, value);
095 }
096
097 @Override public V forcePut(K key, @Nullable V value) {
098 return super.forcePut(key, value);
099 }
100
101 /** Returns the associated key type. */
102 public Class<K> keyType() {
103 return keyType;
104 }
105
106 /**
107 * @serialData the key class, number of entries, first key, first value,
108 * second key, second value, and so on.
109 */
110 @GwtIncompatible("java.io.ObjectOutputStream")
111 private void writeObject(ObjectOutputStream stream) throws IOException {
112 stream.defaultWriteObject();
113 stream.writeObject(keyType);
114 Serialization.writeMap(this, stream);
115 }
116
117 @SuppressWarnings("unchecked") // reading field populated by writeObject
118 @GwtIncompatible("java.io.ObjectInputStream")
119 private void readObject(ObjectInputStream stream)
120 throws IOException, ClassNotFoundException {
121 stream.defaultReadObject();
122 keyType = (Class<K>) stream.readObject();
123 setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
124 new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
125 Serialization.populateMap(this, stream);
126 }
127
128 @GwtIncompatible("only needed in emulated source.")
129 private static final long serialVersionUID = 0;
130 }