001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect; 018 019import com.google.common.annotations.GwtCompatible; 020import com.google.errorprone.annotations.CanIgnoreReturnValue; 021import java.util.Map; 022import java.util.Set; 023import javax.annotation.CheckForNull; 024import org.checkerframework.checker.nullness.qual.Nullable; 025 026/** 027 * A bimap (or "bidirectional map") is a map that preserves the uniqueness of its values as well as 028 * that of its keys. This constraint enables bimaps to support an "inverse view", which is another 029 * bimap containing the same entries as this bimap but with reversed keys and values. 030 * 031 * <p>See the Guava User Guide article on <a href= 032 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">{@code BiMap}</a>. 033 * 034 * @author Kevin Bourrillion 035 * @since 2.0 036 */ 037@GwtCompatible 038@ElementTypesAreNonnullByDefault 039public interface BiMap<K extends @Nullable Object, V extends @Nullable Object> extends Map<K, V> { 040 // Modification Operations 041 042 /** 043 * {@inheritDoc} 044 * 045 * @throws IllegalArgumentException if the given value is already bound to a different key in this 046 * bimap. The bimap will remain unmodified in this event. To avoid this exception, call {@link 047 * #forcePut} instead. 048 */ 049 @CanIgnoreReturnValue 050 @Override 051 @CheckForNull 052 V put(@ParametricNullness K key, @ParametricNullness V value); 053 054 /** 055 * An alternate form of {@code put} that silently removes any existing entry with the value {@code 056 * value} before proceeding with the {@link #put} operation. If the bimap previously contained the 057 * provided key-value mapping, this method has no effect. 058 * 059 * <p>Note that a successful call to this method could cause the size of the bimap to increase by 060 * one, stay the same, or even decrease by one. 061 * 062 * <p><b>Warning:</b> If an existing entry with this value is removed, the key for that entry is 063 * discarded and not returned. 064 * 065 * @param key the key with which the specified value is to be associated 066 * @param value the value to be associated with the specified key 067 * @return the value that was previously associated with the key, or {@code null} if there was no 068 * previous entry. (If the bimap contains null values, then {@code forcePut}, like {@code 069 * put}, returns {@code null} both if the key is absent and if it is present with a null 070 * value.) 071 */ 072 @CanIgnoreReturnValue 073 @CheckForNull 074 V forcePut(@ParametricNullness K key, @ParametricNullness V value); 075 076 // Bulk Operations 077 078 /** 079 * {@inheritDoc} 080 * 081 * <p><b>Warning:</b> the results of calling this method may vary depending on the iteration order 082 * of {@code map}. 083 * 084 * @throws IllegalArgumentException if an attempt to {@code put} any entry fails. Note that some 085 * map entries may have been added to the bimap before the exception was thrown. 086 */ 087 @Override 088 void putAll(Map<? extends K, ? extends V> map); 089 090 // Views 091 092 /** 093 * {@inheritDoc} 094 * 095 * <p>Because a bimap has unique values, this method returns a {@link Set}, instead of the {@link 096 * java.util.Collection} specified in the {@link Map} interface. 097 */ 098 @Override 099 Set<V> values(); 100 101 /** 102 * Returns the inverse view of this bimap, which maps each of this bimap's values to its 103 * associated key. The two bimaps are backed by the same data; any changes to one will appear in 104 * the other. 105 * 106 * <p><b>Note:</b>There is no guaranteed correspondence between the iteration order of a bimap and 107 * that of its inverse. 108 * 109 * @return the inverse view of this bimap 110 */ 111 BiMap<V, K> inverse(); 112}