001    /*
002     * Copyright (C) 2007 Google Inc.
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 java.io.IOException;
020    import java.io.ObjectInputStream;
021    import java.io.ObjectOutputStream;
022    import java.util.EnumMap;
023    import java.util.HashMap;
024    import java.util.Map;
025    
026    import javax.annotation.Nullable;
027    
028    /**
029     * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
030     * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
031     * but null values are. An {@code EnumHashBiMap} and its inverse are both
032     * serializable.
033     *
034     * @author Mike Bostock
035     * @since 2 (imported from Google Collections Library)
036     */
037    public final class EnumHashBiMap<K extends Enum<K>, V>
038        extends AbstractBiMap<K, V> {
039      private transient Class<K> keyType;
040    
041      /**
042       * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
043       *
044       * @param keyType the key type
045       */
046      public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
047          create(Class<K> keyType) {
048        return new EnumHashBiMap<K, V>(keyType);
049      }
050    
051      /**
052       * Constructs a new bimap with the same mappings as the specified map. If the
053       * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new
054       * bimap has the same key type as the input bimap. Otherwise, the specified
055       * map must contain at least one mapping, in order to determine the key type.
056       *
057       * @param map the map whose mappings are to be placed in this map
058       * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an
059       *     {@code EnumHashBiMap} instance and contains no mappings
060       */
061      public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
062          create(Map<K, ? extends V> map) {
063        EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
064        bimap.putAll(map);
065        return bimap;
066      }
067    
068      private EnumHashBiMap(Class<K> keyType) {
069        super(new EnumMap<K, V>(keyType), Maps.<V, K>newHashMapWithExpectedSize(
070            keyType.getEnumConstants().length));
071        this.keyType = keyType;
072      }
073    
074      // Overriding these two methods to show that values may be null (but not keys)
075    
076      @Override public V put(K key, @Nullable V value) {
077        return super.put(key, value);
078      }
079    
080      @Override public V forcePut(K key, @Nullable V value) {
081        return super.forcePut(key, value);
082      }
083    
084      /** Returns the associated key type. */
085      public Class<K> keyType() {
086        return keyType;
087      }
088    
089      /**
090       * @serialData the key class, number of entries, first key, first value,
091       *     second key, second value, and so on.
092       */
093      private void writeObject(ObjectOutputStream stream) throws IOException {
094        stream.defaultWriteObject();
095        stream.writeObject(keyType);
096        Serialization.writeMap(this, stream);
097      }
098    
099      @SuppressWarnings("unchecked") // reading field populated by writeObject
100      private void readObject(ObjectInputStream stream)
101          throws IOException, ClassNotFoundException {
102        stream.defaultReadObject();
103        keyType = (Class<K>) stream.readObject();
104        setDelegates(new EnumMap<K, V>(keyType),
105            new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
106        Serialization.populateMap(this, stream);
107      }
108    
109      private static final long serialVersionUID = 0;
110    }