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
17 package com.google.common.collect;
18
19 import static com.google.common.base.Preconditions.checkArgument;
20 import static com.google.common.base.Preconditions.checkNotNull;
21
22 import com.google.common.annotations.GwtCompatible;
23 import com.google.common.annotations.GwtIncompatible;
24 import java.io.IOException;
25 import java.io.ObjectInputStream;
26 import java.io.ObjectOutputStream;
27 import java.util.EnumMap;
28 import java.util.Map;
29
30 /**
31 * A {@code BiMap} backed by two {@code EnumMap} instances. Null keys and values are not permitted.
32 * An {@code EnumBiMap} and its inverse are both serializable.
33 *
34 * <p>See the Guava User Guide article on <a href=
35 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap"> {@code BiMap}</a>.
36 *
37 * @author Mike Bostock
38 * @since 2.0
39 */
40 @GwtCompatible(emulated = true)
41 public final class EnumBiMap<K extends Enum<K>, V extends Enum<V>> extends AbstractBiMap<K, V> {
42 private transient Class<K> keyType;
43 private transient Class<V> valueType;
44
45 /**
46 * Returns a new, empty {@code EnumBiMap} using the specified key and value types.
47 *
48 * @param keyType the key type
49 * @param valueType the value type
50 */
51 public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V> create(
52 Class<K> keyType, Class<V> valueType) {
53 return new EnumBiMap<>(keyType, valueType);
54 }
55
56 /**
57 * Returns a new bimap with the same mappings as the specified map. If the specified map is an
58 * {@code EnumBiMap}, the new bimap has the same types as the provided map. Otherwise, the
59 * specified map must contain at least one mapping, in order to determine the key and value types.
60 *
61 * @param map the map whose mappings are to be placed in this map
62 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} instance and contains no
63 * mappings
64 */
65 public static <K extends Enum<K>, V extends Enum<V>> EnumBiMap<K, V> create(Map<K, V> map) {
66 EnumBiMap<K, V> bimap = create(inferKeyType(map), inferValueType(map));
67 bimap.putAll(map);
68 return bimap;
69 }
70
71 private EnumBiMap(Class<K> keyType, Class<V> valueType) {
72 super(new EnumMap<K, V>(keyType), new EnumMap<V, K>(valueType));
73 this.keyType = keyType;
74 this.valueType = valueType;
75 }
76
77 static <K extends Enum<K>> Class<K> inferKeyType(Map<K, ?> map) {
78 if (map instanceof EnumBiMap) {
79 return ((EnumBiMap<K, ?>) map).keyType();
80 }
81 if (map instanceof EnumHashBiMap) {
82 return ((EnumHashBiMap<K, ?>) map).keyType();
83 }
84 checkArgument(!map.isEmpty());
85 return map.keySet().iterator().next().getDeclaringClass();
86 }
87
88 private static <V extends Enum<V>> Class<V> inferValueType(Map<?, V> map) {
89 if (map instanceof EnumBiMap) {
90 return ((EnumBiMap<?, V>) map).valueType;
91 }
92 checkArgument(!map.isEmpty());
93 return map.values().iterator().next().getDeclaringClass();
94 }
95
96 /** Returns the associated key type. */
97 public Class<K> keyType() {
98 return keyType;
99 }
100
101 /** Returns the associated value type. */
102 public Class<V> valueType() {
103 return valueType;
104 }
105
106 @Override
107 K checkKey(K key) {
108 return checkNotNull(key);
109 }
110
111 @Override
112 V checkValue(V value) {
113 return checkNotNull(value);
114 }
115
116 /**
117 * @serialData the key class, value class, number of entries, first key, first value, second key,
118 * second value, and so on.
119 */
120 @GwtIncompatible // java.io.ObjectOutputStream
121 private void writeObject(ObjectOutputStream stream) throws IOException {
122 stream.defaultWriteObject();
123 stream.writeObject(keyType);
124 stream.writeObject(valueType);
125 Serialization.writeMap(this, stream);
126 }
127
128 @SuppressWarnings("unchecked") // reading fields populated by writeObject
129 @GwtIncompatible // java.io.ObjectInputStream
130 private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
131 stream.defaultReadObject();
132 keyType = (Class<K>) stream.readObject();
133 valueType = (Class<V>) stream.readObject();
134 setDelegates(new EnumMap<K, V>(keyType), new EnumMap<V, K>(valueType));
135 Serialization.populateMap(this, stream);
136 }
137
138 @GwtIncompatible // not needed in emulated source.
139 private static final long serialVersionUID = 0;
140 }