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.HashMap;
026import java.util.Map;
027
028import javax.annotation.Nullable;
029
030/**
031 * A {@link BiMap} backed by two {@link HashMap} instances. This implementation
032 * allows null keys and values. A {@code HashBiMap} and its inverse are both
033 * serializable.
034 * 
035 * <p>See the Guava User Guide article on <a href=
036 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
037 * {@code BiMap}</a>.
038 *
039 * @author Mike Bostock
040 * @since 2.0 (imported from Google Collections Library)
041 */
042@GwtCompatible(emulated = true)
043public final class HashBiMap<K, V> extends AbstractBiMap<K, V> {
044
045  /**
046   * Returns a new, empty {@code HashBiMap} with the default initial capacity
047   * (16).
048   */
049  public static <K, V> HashBiMap<K, V> create() {
050    return new HashBiMap<K, V>();
051  }
052
053  /**
054   * Constructs a new, empty bimap with the specified expected size.
055   *
056   * @param expectedSize the expected number of entries
057   * @throws IllegalArgumentException if the specified expected size is
058   *     negative
059   */
060  public static <K, V> HashBiMap<K, V> create(int expectedSize) {
061    return new HashBiMap<K, V>(expectedSize);
062  }
063
064  /**
065   * Constructs a new bimap containing initial values from {@code map}. The
066   * bimap is created with an initial capacity sufficient to hold the mappings
067   * in the specified map.
068   */
069  public static <K, V> HashBiMap<K, V> create(
070      Map<? extends K, ? extends V> map) {
071    HashBiMap<K, V> bimap = create(map.size());
072    bimap.putAll(map);
073    return bimap;
074  }
075
076  private HashBiMap() {
077    super(new HashMap<K, V>(), new HashMap<V, K>());
078  }
079
080  private HashBiMap(int expectedSize) {
081    super(
082        Maps.<K, V>newHashMapWithExpectedSize(expectedSize),
083        Maps.<V, K>newHashMapWithExpectedSize(expectedSize));
084  }
085
086  // Override these two methods to show that keys and values may be null
087
088  @Override public V put(@Nullable K key, @Nullable V value) {
089    return super.put(key, value);
090  }
091
092  @Override public V forcePut(@Nullable K key, @Nullable V value) {
093    return super.forcePut(key, value);
094  }
095
096  /**
097   * @serialData the number of entries, first key, first value, second key,
098   *     second value, and so on.
099   */
100  @GwtIncompatible("java.io.ObjectOutputStream")
101  private void writeObject(ObjectOutputStream stream) throws IOException {
102    stream.defaultWriteObject();
103    Serialization.writeMap(this, stream);
104  }
105
106  @GwtIncompatible("java.io.ObjectInputStream")
107  private void readObject(ObjectInputStream stream)
108      throws IOException, ClassNotFoundException {
109    stream.defaultReadObject();
110    int size = Serialization.readCount(stream);
111    setDelegates(Maps.<K, V>newHashMapWithExpectedSize(size),
112        Maps.<V, K>newHashMapWithExpectedSize(size));
113    Serialization.populateMap(this, stream, size);
114  }
115
116  @GwtIncompatible("Not needed in emulated source")
117  private static final long serialVersionUID = 0;
118}