1 /* 2 * Copyright (C) 2007 Google Inc. 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 java.io.IOException; 20 import java.io.ObjectInputStream; 21 import java.io.ObjectOutputStream; 22 import java.util.EnumMap; 23 import java.util.HashMap; 24 import java.util.Map; 25 26 import javax.annotation.Nullable; 27 28 /** 29 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and 30 * a {@code HashMap} instance for values-to-keys. Null keys are not permitted, 31 * but null values are. An {@code EnumHashBiMap} and its inverse are both 32 * serializable. 33 * 34 * @author Mike Bostock 35 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library) 36 */ 37 public final class EnumHashBiMap<K extends Enum<K>, V> 38 extends AbstractBiMap<K, V> { 39 private transient Class<K> keyType; 40 41 /** 42 * Returns a new, empty {@code EnumHashBiMap} using the specified key type. 43 * 44 * @param keyType the key type 45 */ 46 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> 47 create(Class<K> keyType) { 48 return new EnumHashBiMap<K, V>(keyType); 49 } 50 51 /** 52 * Constructs a new bimap with the same mappings as the specified map. If the 53 * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new 54 * bimap has the same key type as the input bimap. Otherwise, the specified 55 * map must contain at least one mapping, in order to determine the key type. 56 * 57 * @param map the map whose mappings are to be placed in this map 58 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an 59 * {@code EnumHashBiMap} instance and contains no mappings 60 */ 61 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> 62 create(Map<K, ? extends V> map) { 63 EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map)); 64 bimap.putAll(map); 65 return bimap; 66 } 67 68 private EnumHashBiMap(Class<K> keyType) { 69 super(new EnumMap<K, V>(keyType), Maps.<V, K>newHashMapWithExpectedSize( 70 keyType.getEnumConstants().length)); 71 this.keyType = keyType; 72 } 73 74 // Overriding these two methods to show that values may be null (but not keys) 75 76 @Override public V put(K key, @Nullable V value) { 77 return super.put(key, value); 78 } 79 80 @Override public V forcePut(K key, @Nullable V value) { 81 return super.forcePut(key, value); 82 } 83 84 /** Returns the associated key type. */ 85 public Class<K> keyType() { 86 return keyType; 87 } 88 89 /** 90 * @serialData the key class, number of entries, first key, first value, 91 * second key, second value, and so on. 92 */ 93 private void writeObject(ObjectOutputStream stream) throws IOException { 94 stream.defaultWriteObject(); 95 stream.writeObject(keyType); 96 Serialization.writeMap(this, stream); 97 } 98 99 @SuppressWarnings("unchecked") // reading field populated by writeObject 100 private void readObject(ObjectInputStream stream) 101 throws IOException, ClassNotFoundException { 102 stream.defaultReadObject(); 103 keyType = (Class<K>) stream.readObject(); 104 setDelegates(new EnumMap<K, V>(keyType), 105 new HashMap<V, K>(keyType.getEnumConstants().length * 3 / 2)); 106 Serialization.populateMap(this, stream); 107 } 108 109 private static final long serialVersionUID = 0; 110 } 111
