MapBackedSet.java

/*
 * (C) 2007-2012 Alibaba Group Holding Limited.
 * 
 * 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.taobao.gecko.service.timer;

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

/**
 * 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) $
 */
public 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();
    }
}