1 /* 2 * Copyright (C) 2008 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.collect.CollectPreconditions.checkEntryNotNull; 20 21 import com.google.common.annotations.GwtCompatible; 22 23 import javax.annotation.Nullable; 24 25 /** 26 * Implementation of {@link ImmutableMap} with exactly one entry. 27 * 28 * @author Jesse Wilson 29 * @author Kevin Bourrillion 30 */ 31 @GwtCompatible(serializable = true, emulated = true) 32 @SuppressWarnings("serial") // uses writeReplace(), not default serialization 33 final class SingletonImmutableBiMap<K, V> extends ImmutableBiMap<K, V> { 34 35 final transient K singleKey; 36 final transient V singleValue; 37 38 SingletonImmutableBiMap(K singleKey, V singleValue) { 39 checkEntryNotNull(singleKey, singleValue); 40 this.singleKey = singleKey; 41 this.singleValue = singleValue; 42 } 43 44 private SingletonImmutableBiMap(K singleKey, V singleValue, 45 ImmutableBiMap<V, K> inverse) { 46 this.singleKey = singleKey; 47 this.singleValue = singleValue; 48 this.inverse = inverse; 49 } 50 51 SingletonImmutableBiMap(Entry<? extends K, ? extends V> entry) { 52 this(entry.getKey(), entry.getValue()); 53 } 54 55 @Override public V get(@Nullable Object key) { 56 return singleKey.equals(key) ? singleValue : null; 57 } 58 59 @Override 60 public int size() { 61 return 1; 62 } 63 64 @Override public boolean containsKey(@Nullable Object key) { 65 return singleKey.equals(key); 66 } 67 68 @Override public boolean containsValue(@Nullable Object value) { 69 return singleValue.equals(value); 70 } 71 72 @Override boolean isPartialView() { 73 return false; 74 } 75 76 @Override 77 ImmutableSet<Entry<K, V>> createEntrySet() { 78 return ImmutableSet.of(Maps.immutableEntry(singleKey, singleValue)); 79 } 80 81 @Override 82 ImmutableSet<K> createKeySet() { 83 return ImmutableSet.of(singleKey); 84 } 85 86 transient ImmutableBiMap<V, K> inverse; 87 88 @Override 89 public ImmutableBiMap<V, K> inverse() { 90 // racy single-check idiom 91 ImmutableBiMap<V, K> result = inverse; 92 if (result == null) { 93 return inverse = new SingletonImmutableBiMap<V, K>( 94 singleValue, singleKey, this); 95 } else { 96 return result; 97 } 98 } 99 } 100
