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/*
* 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 com.google.common.annotations.GwtCompatible;
import java.util.Map;
import javax.annotation.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 SingletonImmutableMap<K, V> extends ImmutableMap<K, V> {
final transient K singleKey;
final transient V singleValue;
SingletonImmutableMap(K singleKey, V singleValue) {
this.singleKey = singleKey;
this.singleValue = singleValue;
}
SingletonImmutableMap(Entry<K, V> entry) {
this(entry.getKey(), entry.getValue());
}
@Override public V get(@Nullable Object key) {
return singleKey.equals(key) ? singleValue : null;
}
@Override
public int size() {
return 1;
}
@Override public boolean isEmpty() {
return false;
}
@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);
}
@Override
ImmutableCollection<V> createValues() {
return ImmutableList.of(singleValue);
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof Map) {
Map<?, ?> that = (Map<?, ?>) object;
if (that.size() == 1) {
Entry<?, ?> entry = that.entrySet().iterator().next();
return singleKey.equals(entry.getKey())
&& singleValue.equals(entry.getValue());
}
}
return false;
}
@Override public int hashCode() {
return singleKey.hashCode() ^ singleValue.hashCode();
}
}
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