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