    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    }