| /* |
| * Copyright (C) 2008 The Guava Authors |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.google.common.collect; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| import static com.google.common.collect.CollectPreconditions.checkEntryNotNull; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.errorprone.annotations.concurrent.LazyInit; |
| import com.google.j2objc.annotations.RetainedWith; |
| import java.util.function.BiConsumer; |
| import org.checkerframework.checker.nullness.qual.Nullable; |
| |
| /** |
| * Implementation of {@link ImmutableMap} with exactly one entry. |
| * |
| * @author Jesse Wilson |
| * @author Kevin Bourrillion |
| */ |
| @GwtCompatible(serializable = true, emulated = true) |
| @SuppressWarnings("serial") // uses writeReplace(), not default serialization |
| final class SingletonImmutableBiMap<K, V> extends ImmutableBiMap<K, V> { |
| |
| final transient K singleKey; |
| final transient V singleValue; |
| |
| SingletonImmutableBiMap(K singleKey, V singleValue) { |
| checkEntryNotNull(singleKey, singleValue); |
| this.singleKey = singleKey; |
| this.singleValue = singleValue; |
| } |
| |
| private SingletonImmutableBiMap(K singleKey, V singleValue, ImmutableBiMap<V, K> inverse) { |
| this.singleKey = singleKey; |
| this.singleValue = singleValue; |
| this.inverse = inverse; |
| } |
| |
| @Override |
| public V get(@Nullable Object key) { |
| return singleKey.equals(key) ? singleValue : null; |
| } |
| |
| @Override |
| public int size() { |
| return 1; |
| } |
| |
| @Override |
| public void forEach(BiConsumer<? super K, ? super V> action) { |
| checkNotNull(action).accept(singleKey, singleValue); |
| } |
| |
| @Override |
| public boolean containsKey(@Nullable Object key) { |
| return singleKey.equals(key); |
| } |
| |
| @Override |
| public boolean containsValue(@Nullable Object value) { |
| return singleValue.equals(value); |
| } |
| |
| @Override |
| boolean isPartialView() { |
| return false; |
| } |
| |
| @Override |
| ImmutableSet<Entry<K, V>> createEntrySet() { |
| return ImmutableSet.of(Maps.immutableEntry(singleKey, singleValue)); |
| } |
| |
| @Override |
| ImmutableSet<K> createKeySet() { |
| return ImmutableSet.of(singleKey); |
| } |
| |
| @LazyInit @RetainedWith transient ImmutableBiMap<V, K> inverse; |
| |
| @Override |
| public ImmutableBiMap<V, K> inverse() { |
| // racy single-check idiom |
| ImmutableBiMap<V, K> result = inverse; |
| if (result == null) { |
| return inverse = new SingletonImmutableBiMap<>(singleValue, singleKey, this); |
| } else { |
| return result; |
| } |
| } |
| } |