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 com.google.common.annotations.GwtCompatible; 20 21import java.util.EnumMap; 22import java.util.Map; 23 24import javax.annotation.Nullable; 25 26/** 27 * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and 28 * a {@code HashMap} instance for values-to-keys. Null keys are not permitted, 29 * but null values are. An {@code EnumHashBiMap} and its inverse are both 30 * serializable. 31 * 32 * @author Mike Bostock 33 * @since 2.0 (imported from Google Collections Library) 34 */ 35@GwtCompatible(emulated = true) 36public final class EnumHashBiMap<K extends Enum<K>, V> 37 extends AbstractBiMap<K, V> { 38 private transient Class<K> keyType; 39 40 /** 41 * Returns a new, empty {@code EnumHashBiMap} using the specified key type. 42 * 43 * @param keyType the key type 44 */ 45 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> 46 create(Class<K> keyType) { 47 return new EnumHashBiMap<K, V>(keyType); 48 } 49 50 /** 51 * Constructs a new bimap with the same mappings as the specified map. If the 52 * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new 53 * bimap has the same key type as the input bimap. Otherwise, the specified 54 * map must contain at least one mapping, in order to determine the key type. 55 * 56 * @param map the map whose mappings are to be placed in this map 57 * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an 58 * {@code EnumHashBiMap} instance and contains no mappings 59 */ 60 public static <K extends Enum<K>, V> EnumHashBiMap<K, V> 61 create(Map<K, ? extends V> map) { 62 EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map)); 63 bimap.putAll(map); 64 return bimap; 65 } 66 67 private EnumHashBiMap(Class<K> keyType) { 68 super(WellBehavedMap.wrap( 69 new EnumMap<K, V>(keyType)), 70 Maps.<V, K>newHashMapWithExpectedSize( 71 keyType.getEnumConstants().length)); 72 this.keyType = keyType; 73 } 74 75 // Overriding these two methods to show that values may be null (but not keys) 76 77 @Override public V put(K key, @Nullable V value) { 78 return super.put(key, value); 79 } 80 81 @Override public V forcePut(K key, @Nullable V value) { 82 return super.forcePut(key, value); 83 } 84 85 /** Returns the associated key type. */ 86 public Class<K> keyType() { 87 return keyType; 88 } 89} 90 91