    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.EnumMap;
    026    import java.util.HashMap;
    027    import java.util.Map;
    028
    029    import javax.annotation.Nullable;
    030
    031    /**
    032     * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
    033     * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
    034     * but null values are. An {@code EnumHashBiMap} and its inverse are both
    035     * serializable.
    036     *
    037     * @author Mike Bostock
    038     * @since 2.0 (imported from Google Collections Library)
    039     */
    040    @GwtCompatible(emulated = true)
    041    public final class EnumHashBiMap<K extends Enum<K>, V>
    042        extends AbstractBiMap<K, V> {
    043      private transient Class<K> keyType;
    044
    045      /**
    046       * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
    047       *
    048       * @param keyType the key type
    049       */
    050      public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
    051          create(Class<K> keyType) {
    052        return new EnumHashBiMap<K, V>(keyType);
    053      }
    054
    055      /**
    056       * Constructs a new bimap with the same mappings as the specified map. If the
    057       * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new
    058       * bimap has the same key type as the input bimap. Otherwise, the specified
    059       * map must contain at least one mapping, in order to determine the key type.
    060       *
    061       * @param map the map whose mappings are to be placed in this map
    062       * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an
    063       *     {@code EnumHashBiMap} instance and contains no mappings
    064       */
    065      public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
    066          create(Map<K, ? extends V> map) {
    067        EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
    068        bimap.putAll(map);
    069        return bimap;
    070      }
    071
    072      private EnumHashBiMap(Class<K> keyType) {
    073        super(WellBehavedMap.wrap(
    074            new EnumMap<K, V>(keyType)),
    075            Maps.<V, K>newHashMapWithExpectedSize(
    076                keyType.getEnumConstants().length));
    077        this.keyType = keyType;
    078      }
    079
    080      // Overriding these two methods to show that values may be null (but not keys)
    081
    082      @Override public V put(K key, @Nullable V value) {
    083        return super.put(key, value);
    084      }
    085
    086      @Override public V forcePut(K key, @Nullable V value) {
    087        return super.forcePut(key, value);
    088      }
    089
    090      /** Returns the associated key type. */
    091      public Class<K> keyType() {
    092        return keyType;
    093      }
    094
    095      /**
    096       * @serialData the key class, number of entries, first key, first value,
    097       *     second key, second value, and so on.
    098       */
    099      @GwtIncompatible("java.io.ObjectOutputStream")
    100      private void writeObject(ObjectOutputStream stream) throws IOException {
    101        stream.defaultWriteObject();
    102        stream.writeObject(keyType);
    103        Serialization.writeMap(this, stream);
    104      }
    105
    106      @SuppressWarnings("unchecked") // reading field populated by writeObject
    107      @GwtIncompatible("java.io.ObjectInputStream")
    108      private void readObject(ObjectInputStream stream)
    109          throws IOException, ClassNotFoundException {
    110        stream.defaultReadObject();
    111        keyType = (Class<K>) stream.readObject();
    112        setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
    113            new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
    114        Serialization.populateMap(this, stream);
    115      }
    116
    117      @GwtIncompatible("only needed in emulated source.")
    118      private static final long serialVersionUID = 0;
    119    }