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