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 com.google.common.annotations.GwtCompatible;
020import com.google.common.annotations.GwtIncompatible;
021
022import java.io.IOException;
023import java.io.ObjectInputStream;
024import java.io.ObjectOutputStream;
025import java.util.EnumMap;
026import java.util.HashMap;
027import java.util.Map;
028
029import 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 (imported from Google Collections Library)
039 */
040@GwtCompatible(emulated = true)
041public 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(new EnumMap<K, V>(keyType)),
074        Maps.<V, K>newHashMapWithExpectedSize(keyType.getEnumConstants().length));
075    this.keyType = keyType;
076  }
077
078  // Overriding these two methods to show that values may be null (but not keys)
079
080  @Override public V put(K key, @Nullable V value) {
081    return super.put(key, value);
082  }
083
084  @Override public V forcePut(K key, @Nullable V value) {
085    return super.forcePut(key, value);
086  }
087
088  /** Returns the associated key type. */
089  public Class<K> keyType() {
090    return keyType;
091  }
092
093  /**
094   * @serialData the key class, number of entries, first key, first value,
095   *     second key, second value, and so on.
096   */
097  @GwtIncompatible("java.io.ObjectOutputStream")
098  private void writeObject(ObjectOutputStream stream) throws IOException {
099    stream.defaultWriteObject();
100    stream.writeObject(keyType);
101    Serialization.writeMap(this, stream);
102  }
103
104  @SuppressWarnings("unchecked") // reading field populated by writeObject
105  @GwtIncompatible("java.io.ObjectInputStream")
106  private void readObject(ObjectInputStream stream)
107      throws IOException, ClassNotFoundException {
108    stream.defaultReadObject();
109    keyType = (Class<K>) stream.readObject();
110    setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
111        new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
112    Serialization.populateMap(this, stream);
113  }
114
115  @GwtIncompatible("only needed in emulated source.")
116  private static final long serialVersionUID = 0;
117}