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/*
* Copyright (C) 2009 Google Inc.
*
* 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 java.util.concurrent;
import java.util.AbstractMap;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
/**
* Minimal emulation of {@link java.util.concurrent.ConcurrentHashMap}.
* Note that javascript intepreter is <a
* href="http://code.google.com/docreader/#p=google-web-toolkit-doc-1-5&t=DevGuideJavaCompatibility">
* single-threaded</a>, it is essentially a {@link java.util.HashMap},
* implementing the new methods introduced by {@link ConcurrentMap}.
*
* @author Hayward Chan
*/
public class ConcurrentHashMap<K, V>
extends AbstractMap<K, V> implements ConcurrentMap<K, V> {
private final Map<K, V> backingMap;
public ConcurrentHashMap() {
this.backingMap = new HashMap<K, V>();
}
public ConcurrentHashMap(int initialCapacity) {
this.backingMap = new HashMap<K, V>(initialCapacity);
}
public ConcurrentHashMap(int initialCapacity, float loadFactor) {
this.backingMap = new HashMap<K, V>(initialCapacity, loadFactor);
}
public ConcurrentHashMap(Map<? extends K, ? extends V> t) {
this.backingMap = new HashMap<K, V>(t);
}
public V putIfAbsent(K key, V value) {
if (!containsKey(key)) {
return put(key, value);
} else {
return get(key);
}
}
public boolean remove(Object key, Object value) {
if (containsKey(key) && get(key).equals(value)) {
remove(key);
return true;
} else {
return false;
}
}
public boolean replace(K key, V oldValue, V newValue) {
if (oldValue == null || newValue == null) {
throw new NullPointerException();
} else if (containsKey(key) && get(key).equals(oldValue)) {
put(key, newValue);
return true;
} else {
return false;
}
}
public V replace(K key, V value) {
if (value == null) {
throw new NullPointerException();
} else if (containsKey(key)) {
return put(key, value);
} else {
return null;
}
}
@Override public boolean containsKey(Object key) {
if (key == null) {
throw new NullPointerException();
}
return backingMap.containsKey(key);
}
@Override public V get(Object key) {
if (key == null) {
throw new NullPointerException();
}
return backingMap.get(key);
}
@Override public V put(K key, V value) {
if (key == null || value == null) {
throw new NullPointerException();
}
return backingMap.put(key, value);
}
@Override public boolean containsValue(Object value) {
if (value == null) {
throw new NullPointerException();
}
return backingMap.containsValue(value);
}
@Override public V remove(Object key) {
if (key == null) {
throw new NullPointerException();
}
return backingMap.remove(key);
}
@Override public Set<Entry<K, V>> entrySet() {
return backingMap.entrySet();
}
public boolean contains(Object value) {
return containsValue(value);
}
public Enumeration<V> elements() {
return Collections.enumeration(values());
}
public Enumeration<K> keys() {
return Collections.enumeration(keySet());
}
}
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