    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     * @author Mike Bostock
    036     * @since 2.0 (imported from Google Collections Library)
    037     */
    038    @GwtCompatible(emulated = true)
    039    public 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(
    078            Maps.<K, V>newHashMapWithExpectedSize(expectedSize),
    079            Maps.<V, K>newHashMapWithExpectedSize(expectedSize));
    080      }
    081
    082      // Override these two methods to show that keys and values may be null
    083
    084      @Override public V put(@Nullable K key, @Nullable V value) {
    085        return super.put(key, value);
    086      }
    087
    088      @Override public V forcePut(@Nullable K key, @Nullable V value) {
    089        return super.forcePut(key, value);
    090      }
    091
    092      /**
    093       * @serialData the number of entries, first key, first value, second key,
    094       *     second value, and so on.
    095       */
    096      @GwtIncompatible("java.io.ObjectOutputStream")
    097      private void writeObject(ObjectOutputStream stream) throws IOException {
    098        stream.defaultWriteObject();
    099        Serialization.writeMap(this, stream);
    100      }
    101
    102      @GwtIncompatible("java.io.ObjectInputStream")
    103      private void readObject(ObjectInputStream stream)
    104          throws IOException, ClassNotFoundException {
    105        stream.defaultReadObject();
    106        int size = Serialization.readCount(stream);
    107        setDelegates(Maps.<K, V>newHashMapWithExpectedSize(size),
    108            Maps.<V, K>newHashMapWithExpectedSize(size));
    109        Serialization.populateMap(this, stream, size);
    110      }
    111
    112      @GwtIncompatible("Not needed in emulated source")
    113      private static final long serialVersionUID = 0;
    114    }