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 * "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)
047public 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 3 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}