/**
 * 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.util.Collection;
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;
  }
}