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.checkNotNull;
20
21 import com.google.common.annotations.GwtCompatible;
22 import com.google.common.annotations.GwtIncompatible;
23 import com.google.errorprone.annotations.CanIgnoreReturnValue;
24 import java.io.IOException;
25 import java.io.ObjectInputStream;
26 import java.io.ObjectOutputStream;
27 import java.util.EnumMap;
28 import java.util.HashMap;
29 import java.util.Map;
30 import org.checkerframework.checker.nullness.qual.Nullable;
31
32 /**
33 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and a {@code HashMap}
34 * instance for values-to-keys. Null keys are not permitted, but null values are. An {@code
35 * EnumHashBiMap} and its inverse are both serializable.
36 *
37 * <p>See the Guava User Guide article on <a href=
38 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap"> {@code BiMap}</a>.
39 *
40 * @author Mike Bostock
41 * @since 2.0
42 */
43 @GwtCompatible(emulated = true)
44 public final class EnumHashBiMap<K extends Enum<K>, V> extends AbstractBiMap<K, V> {
45 private transient Class<K> keyType;
46
47 /**
48 * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
49 *
50 * @param keyType the key type
51 */
52 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> create(Class<K> keyType) {
53 return new EnumHashBiMap<>(keyType);
54 }
55
56 /**
57 * Constructs a new bimap with the same mappings as the specified map. If the specified map is an
58 * {@code EnumHashBiMap} or an {@link EnumBiMap}, the new bimap has the same key type as the input
59 * bimap. Otherwise, the specified map must contain at least one mapping, in order to determine
60 * the key type.
61 *
62 * @param map the map whose mappings are to be placed in this map
63 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an {@code EnumHashBiMap}
64 * instance and contains no mappings
65 */
66 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> create(Map<K, ? extends V> map) {
67 EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
68 bimap.putAll(map);
69 return bimap;
70 }
71
72 private EnumHashBiMap(Class<K> keyType) {
73 super(
74 new EnumMap<K, V>(keyType),
75 Maps.<V, K>newHashMapWithExpectedSize(keyType.getEnumConstants().length));
76 this.keyType = keyType;
77 }
78
79 // Overriding these 3 methods to show that values may be null (but not keys)
80
81 @Override
82 K checkKey(K key) {
83 return checkNotNull(key);
84 }
85
86 @CanIgnoreReturnValue
87 @Override
88 public V put(K key, @Nullable V value) {
89 return super.put(key, value);
90 }
91
92 @CanIgnoreReturnValue
93 @Override
94 public V forcePut(K key, @Nullable V value) {
95 return super.forcePut(key, value);
96 }
97
98 /** Returns the associated key type. */
99 public Class<K> keyType() {
100 return keyType;
101 }
102
103 /**
104 * @serialData the key class, number of entries, first key, first value, second key, second value,
105 * and so on.
106 */
107 @GwtIncompatible // java.io.ObjectOutputStream
108 private void writeObject(ObjectOutputStream stream) throws IOException {
109 stream.defaultWriteObject();
110 stream.writeObject(keyType);
111 Serialization.writeMap(this, stream);
112 }
113
114 @SuppressWarnings("unchecked") // reading field populated by writeObject
115 @GwtIncompatible // java.io.ObjectInputStream
116 private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
117 stream.defaultReadObject();
118 keyType = (Class<K>) stream.readObject();
119 setDelegates(
120 new EnumMap<K, V>(keyType), new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2));
121 Serialization.populateMap(this, stream);
122 }
123
124 @GwtIncompatible // only needed in emulated source.
125 private static final long serialVersionUID = 0;
126 }