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    
017    package com.google.common.collect;
018    
019    import com.google.common.annotations.GwtCompatible;
020    import com.google.common.annotations.GwtIncompatible;
021    
022    import java.io.IOException;
023    import java.io.ObjectInputStream;
024    import java.io.ObjectOutputStream;
025    import java.util.HashMap;
026    import java.util.Map;
027    
028    import 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)
043    public 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    }