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 * @author Mike Bostock
036 * @since 2 (imported from Google Collections Library)
037 */
038@GwtCompatible(emulated = true)
039public final class HashBiMap<K, V> extends AbstractBiMap<K, V> {
040
041  /**
042   * Returns a new, empty {@code HashBiMap} with the default initial capacity
043   * (16).
044   */
045  public static <K, V> HashBiMap<K, V> create() {
046    return new HashBiMap<K, V>();
047  }
048
049  /**
050   * Constructs a new, empty bimap with the specified expected size.
051   *
052   * @param expectedSize the expected number of entries
053   * @throws IllegalArgumentException if the specified expected size is
054   *     negative
055   */
056  public static <K, V> HashBiMap<K, V> create(int expectedSize) {
057    return new HashBiMap<K, V>(expectedSize);
058  }
059
060  /**
061   * Constructs a new bimap containing initial values from {@code map}. The
062   * bimap is created with an initial capacity sufficient to hold the mappings
063   * in the specified map.
064   */
065  public static <K, V> HashBiMap<K, V> create(
066      Map<? extends K, ? extends V> map) {
067    HashBiMap<K, V> bimap = create(map.size());
068    bimap.putAll(map);
069    return bimap;
070  }
071
072  private HashBiMap() {
073    super(new HashMap<K, V>(), new HashMap<V, K>());
074  }
075
076  private HashBiMap(int expectedSize) {
077    super(new HashMap<K, V>(Maps.capacity(expectedSize)),
078        new HashMap<V, K>(Maps.capacity(expectedSize)));
079  }
080
081  // Override these two methods to show that keys and values may be null
082
083  @Override public V put(@Nullable K key, @Nullable V value) {
084    return super.put(key, value);
085  }
086
087  @Override public V forcePut(@Nullable K key, @Nullable V value) {
088    return super.forcePut(key, value);
089  }
090
091  /**
092   * @serialData the number of entries, first key, first value, second key,
093   *     second value, and so on.
094   */
095  @GwtIncompatible("java.io.ObjectOutputStream")
096  private void writeObject(ObjectOutputStream stream) throws IOException {
097    stream.defaultWriteObject();
098    Serialization.writeMap(this, stream);
099  }
100
101  @GwtIncompatible("java.io.ObjectInputStream")
102  private void readObject(ObjectInputStream stream)
103      throws IOException, ClassNotFoundException {
104    stream.defaultReadObject();
105    int size = Serialization.readCount(stream);
106    setDelegates(Maps.<K, V>newHashMapWithExpectedSize(size),
107        Maps.<V, K>newHashMapWithExpectedSize(size));
108    Serialization.populateMap(this, stream, size);
109  }
110
111  @GwtIncompatible("Not needed in emulated source")
112  private static final long serialVersionUID = 0;
113}