EnumBiMap.java revision 3c77433663281544363151bf284b0240dfd22a42 
1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import static com.google.common.base.Preconditions.checkArgument;
20import static com.google.common.base.Preconditions.checkNotNull;
21
22import com.google.common.annotations.GwtCompatible;
23import com.google.common.annotations.GwtIncompatible;
24
25import java.io.IOException;
26import java.io.ObjectInputStream;
27import java.io.ObjectOutputStream;
28import java.util.EnumMap;
29import java.util.Map;
30
31/**
32 * A {@code BiMap} backed by two {@code EnumMap} instances. Null keys and values
33 * are not permitted. An {@code EnumBiMap} and its inverse are both
34 * serializable.
35 *
36 * <p>See the Guava User Guide article on <a href=
37 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
38 * {@code BiMap}</a>.
39 *
40 * @author Mike Bostock
41 * @since 2.0 (imported from Google Collections Library)
42 */
43@GwtCompatible(emulated = true)
44public final class EnumBiMap<K extends Enum<K>, V extends Enum<V>>
45    extends AbstractBiMap<K, V> {
46  private transient Class<K> keyType;
47  private transient Class<V> valueType;
48
49  /**
50   * Returns a new, empty {@code EnumBiMap} using the specified key and value
51   * types.
52   *
53   * @param keyType the key type
54   * @param valueType the value type
55   */
56  public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V>
57      create(Class<K> keyType, Class<V> valueType) {
58    return new EnumBiMap<K, V>(keyType, valueType);
59  }
60
61  /**
62   * Returns a new bimap with the same mappings as the specified map. If the
63   * specified map is an {@code EnumBiMap}, the new bimap has the same types as
64   * the provided map. Otherwise, the specified map must contain at least one
65   * mapping, in order to determine the key and value types.
66   *
67   * @param map the map whose mappings are to be placed in this map
68   * @throws IllegalArgumentException if map is not an {@code EnumBiMap}
69   *     instance and contains no mappings
70   */
71  public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V>
72      create(Map<K, V> map) {
73    EnumBiMap<K, V> bimap = create(inferKeyType(map), inferValueType(map));
74    bimap.putAll(map);
75    return bimap;
76  }
77
78  private EnumBiMap(Class<K> keyType, Class<V> valueType) {
79    super(WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
80        WellBehavedMap.wrap(new EnumMap<V, K>(valueType)));
81    this.keyType = keyType;
82    this.valueType = valueType;
83  }
84
85  static <K extends Enum<K>> Class<K> inferKeyType(Map<K, ?> map) {
86    if (map instanceof EnumBiMap) {
87      return ((EnumBiMap<K, ?>) map).keyType();
88    }
89    if (map instanceof EnumHashBiMap) {
90      return ((EnumHashBiMap<K, ?>) map).keyType();
91    }
92    checkArgument(!map.isEmpty());
93    return map.keySet().iterator().next().getDeclaringClass();
94  }
95
96  private static <V extends Enum<V>> Class<V> inferValueType(Map<?, V> map) {
97    if (map instanceof EnumBiMap) {
98      return ((EnumBiMap<?, V>) map).valueType;
99    }
100    checkArgument(!map.isEmpty());
101    return map.values().iterator().next().getDeclaringClass();
102  }
103
104  /** Returns the associated key type. */
105  public Class<K> keyType() {
106    return keyType;
107  }
108
109  /** Returns the associated value type. */
110  public Class<V> valueType() {
111    return valueType;
112  }
113
114  @Override
115  K checkKey(K key) {
116    return checkNotNull(key);
117  }
118
119  @Override
120  V checkValue(V value) {
121    return checkNotNull(value);
122  }
123
124  /**
125   * @serialData the key class, value class, number of entries, first key, first
126   *     value, second key, second value, and so on.
127   */
128  @GwtIncompatible("java.io.ObjectOutputStream")
129  private void writeObject(ObjectOutputStream stream) throws IOException {
130    stream.defaultWriteObject();
131    stream.writeObject(keyType);
132    stream.writeObject(valueType);
133    Serialization.writeMap(this, stream);
134  }
135
136  @SuppressWarnings("unchecked") // reading fields populated by writeObject
137  @GwtIncompatible("java.io.ObjectInputStream")
138  private void readObject(ObjectInputStream stream)
139      throws IOException, ClassNotFoundException {
140    stream.defaultReadObject();
141    keyType = (Class<K>) stream.readObject();
142    valueType = (Class<V>) stream.readObject();
143    setDelegates(
144        WellBehavedMap.wrap(new EnumMap<K, V>(keyType)),
145        WellBehavedMap.wrap(new EnumMap<V, K>(valueType)));
146    Serialization.populateMap(this, stream);
147  }
148
149  @GwtIncompatible("not needed in emulated source.")
150  private static final long serialVersionUID = 0;
151}
152