ConcurrentHashSet.java Source code

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Here is the source code for ConcurrentHashSet.java

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/**
 *Copyright [2009-2010] [dennis zhuang(killme2008@gmail.com)]
 *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
 */
/**
 *Copyright [2009-2010] [dennis zhuang(killme2008@gmail.com)]
 *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.code.yanf4j.util;

import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * A {@link ConcurrentHashMap}-backed {@link Set}.
 * 
 * @author The Apache MINA Project (dev@mina.apache.org)
 * @version $Rev: 597692 $, $Date: 2007-11-23 08:56:32 -0700 (Fri, 23 Nov 2007)
 *          $
 */
public class ConcurrentHashSet<E> extends MapBackedSet<E> {

    private static final long serialVersionUID = 8518578988740277828L;

    public ConcurrentHashSet() {
        super(new ConcurrentHashMap<E, Boolean>());
    }

    public ConcurrentHashSet(Collection<E> c) {
        super(new ConcurrentHashMap<E, Boolean>(), c);
    }

    @Override
    public boolean add(E o) {
        Boolean answer = ((ConcurrentMap<E, Boolean>) map).putIfAbsent(o, Boolean.TRUE);
        return answer == null;
    }
}

/**
 * A {@link Map}-backed {@link Set}.
 * 
 * @author The Apache MINA Project (dev@mina.apache.org)
 * @version $Rev: 597692 $, $Date: 2007-11-23 08:56:32 -0700 (Fri, 23 Nov 2007)
 *          $
 */
class MapBackedSet<E> extends AbstractSet<E> implements Serializable {

    private static final long serialVersionUID = -8347878570391674042L;

    protected final Map<E, Boolean> map;

    public MapBackedSet(Map<E, Boolean> map) {
        this.map = map;
    }

    public MapBackedSet(Map<E, Boolean> map, Collection<E> c) {
        this.map = map;
        addAll(c);
    }

    @Override
    public int size() {
        return map.size();
    }

    @Override
    public boolean contains(Object o) {
        return map.containsKey(o);
    }

    @Override
    public Iterator<E> iterator() {
        return map.keySet().iterator();
    }

    @Override
    public boolean add(E o) {
        return map.put(o, Boolean.TRUE) == null;
    }

    @Override
    public boolean remove(Object o) {
        return map.remove(o) != null;
    }

    @Override
    public void clear() {
        map.clear();
    }
}