/*
* 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;
private transient Entry<K, V> entry;
SingletonImmutableMap(K singleKey, V singleValue) {
this.singleKey = singleKey;
this.singleValue = singleValue;
}
SingletonImmutableMap(Entry<K, V> entry) {
this.entry = entry;
this.singleKey = entry.getKey();
this.singleValue = entry.getValue();
}
private Entry<K, V> entry() {
Entry<K, V> e = entry;
return (e == null)
? (entry = Maps.immutableEntry(singleKey, singleValue)) : e;
}
@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;
}
private transient ImmutableSet<Entry<K, V>> entrySet;
@Override public ImmutableSet<Entry<K, V>> entrySet() {
ImmutableSet<Entry<K, V>> es = entrySet;
return (es == null) ? (entrySet = ImmutableSet.of(entry())) : es;
}
private transient ImmutableSet<K> keySet;
@Override public ImmutableSet<K> keySet() {
ImmutableSet<K> ks = keySet;
return (ks == null) ? (keySet = ImmutableSet.of(singleKey)) : ks;
}
private transient ImmutableCollection<V> values;
@Override public ImmutableCollection<V> values() {
ImmutableCollection<V> v = values;
return (v == null) ? (values = new Values<V>(singleValue)) : v;
}
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
private static class Values<V> extends ImmutableCollection<V> {
final V singleValue;
Values(V singleValue) {
this.singleValue = singleValue;
}
@Override public boolean contains(Object object) {
return singleValue.equals(object);
}
@Override public boolean isEmpty() {
return false;
}
@Override
public int size() {
return 1;
}
@Override public UnmodifiableIterator<V> iterator() {
return Iterators.singletonIterator(singleValue);
}
@Override boolean isPartialView() {
return true;
}
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof Map) {
Map<?, ?> that = (Map<?, ?>) object;
if (that.size() != 1) {
return false;
}
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();
}
@Override public String toString() {
return new StringBuilder()
.append('{')
.append(singleKey.toString())
.append('=')
.append(singleValue.toString())
.append('}')
.toString();
}
}
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