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.HashMap; 22import java.util.Map; 23 24import javax.annotation.Nullable; 25 26/** 27 * A {@link BiMap} backed by two {@link HashMap} instances. This implementation 28 * allows null keys and values. A {@code HashBiMap} and its inverse are both 29 * serializable. 30 * 31 * @author Mike Bostock 32 * @since 2.0 (imported from Google Collections Library) 33 */ 34@GwtCompatible(emulated = true) 35public final class HashBiMap<K, V> extends AbstractBiMap<K, V> { 36 37 /** 38 * Returns a new, empty {@code HashBiMap} with the default initial capacity 39 * (16). 40 */ 41 public static <K, V> HashBiMap<K, V> create() { 42 return new HashBiMap<K, V>(); 43 } 44 45 /** 46 * Constructs a new, empty bimap with the specified expected size. 47 * 48 * @param expectedSize the expected number of entries 49 * @throws IllegalArgumentException if the specified expected size is 50 * negative 51 */ 52 public static <K, V> HashBiMap<K, V> create(int expectedSize) { 53 return new HashBiMap<K, V>(expectedSize); 54 } 55 56 /** 57 * Constructs a new bimap containing initial values from {@code map}. The 58 * bimap is created with an initial capacity sufficient to hold the mappings 59 * in the specified map. 60 */ 61 public static <K, V> HashBiMap<K, V> create( 62 Map<? extends K, ? extends V> map) { 63 HashBiMap<K, V> bimap = create(map.size()); 64 bimap.putAll(map); 65 return bimap; 66 } 67 68 private HashBiMap() { 69 super(new HashMap<K, V>(), new HashMap<V, K>()); 70 } 71 72 private HashBiMap(int expectedSize) { 73 super( 74 Maps.<K, V>newHashMapWithExpectedSize(expectedSize), 75 Maps.<V, K>newHashMapWithExpectedSize(expectedSize)); 76 } 77 78 // Override these two methods to show that keys and values may be null 79 80 @Override public V put(@Nullable K key, @Nullable V value) { 81 return super.put(key, value); 82 } 83 84 @Override public V forcePut(@Nullable K key, @Nullable V value) { 85 return super.forcePut(key, value); 86 } 87} 88 89