    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 static com.google.common.base.Preconditions.checkNotNull;
    020
    021    import com.google.common.annotations.GwtCompatible;
    022    import com.google.common.annotations.GwtIncompatible;
    023
    024    import java.io.IOException;
    025    import java.io.ObjectInputStream;
    026    import java.io.ObjectOutputStream;
    027    import java.util.EnumMap;
    028    import java.util.HashMap;
    029    import java.util.Map;
    030
    031    import javax.annotation.Nullable;
    032
    033    /**
    034     * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
    035     * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
    036     * but null values are. An {@code EnumHashBiMap} and its inverse are both
    037     * serializable.
    038     *
    039     * <p>See the Guava User Guide article on <a href=
    040     * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
    041     * {@code BiMap}</a>.
    042     *
    043     * @author Mike Bostock
    044     * @since 2.0 (imported from Google Collections Library)
    045     */
    046    @GwtCompatible(emulated = true)
    047    public final class EnumHashBiMap<K extends Enum<K>, V>
    048        extends AbstractBiMap<K, V> {
    049      private transient Class<K> keyType;
    050
    051      /**
    052       * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
    053       *
    054       * @param keyType the key type
    055       */
    056      public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
    057          create(Class<K> keyType) {
    058        return new EnumHashBiMap<K, V>(keyType);
    059      }
    060
    061      /**
    062       * Constructs a new bimap with the same mappings as the specified map. If the
    063       * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new
    064       * bimap has the same key type as the input bimap. Otherwise, the specified
    065       * map must contain at least one mapping, in order to determine the key type.
    066       *
    067       * @param map the map whose mappings are to be placed in this map
    068       * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an
    069       *     {@code EnumHashBiMap} instance and contains no mappings
    070       */
    071      public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
    072          create(Map<K, ? extends V> map) {
    073        EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
    074        bimap.putAll(map);
    075        return bimap;
    076      }
    077
    078      private EnumHashBiMap(Class<K> keyType) {
    079        super(WellBehavedMap.wrap(
    080            new EnumMap<K, V>(keyType)),
    081            Maps.<V, K>newHashMapWithExpectedSize(
    082                keyType.getEnumConstants().length));
    083        this.keyType = keyType;
    084      }
    085
    086      // Overriding these 3 methods to show that values may be null (but not keys)
    087
    088      @Override
    089      K checkKey(K key) {
    090        return checkNotNull(key);
    091      }
    092
    093      @Override public V put(K key, @Nullable V value) {
    094        return super.put(key, value);
    095      }
    096
    097      @Override public V forcePut(K key, @Nullable V value) {
    098        return super.forcePut(key, value);
    099      }
    100
    101      /** Returns the associated key type. */
    102      public Class<K> keyType() {
    103        return keyType;
    104      }
    105
    106      /**
    107       * @serialData the key class, number of entries, first key, first value,
    108       *     second key, second value, and so on.
    109       */
    110      @GwtIncompatible("java.io.ObjectOutputStream")
    111      private void writeObject(ObjectOutputStream stream) throws IOException {
    112        stream.defaultWriteObject();
    113        stream.writeObject(keyType);
    114        Serialization.writeMap(this, stream);
    115      }
    116
    117      @SuppressWarnings("unchecked") // reading field populated by writeObject
    118      @GwtIncompatible("java.io.ObjectInputStream")
    119      private void readObject(ObjectInputStream stream)
    120          throws IOException, ClassNotFoundException {
    121        stream.defaultReadObject();
    122        keyType = (Class<K>) stream.readObject();
    123        setDelegates(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
    124            new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
    125        Serialization.populateMap(this, stream);
    126      }
    127
    128      @GwtIncompatible("only needed in emulated source.")
    129      private static final long serialVersionUID = 0;
    130    }