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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * 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. See accompanying
 * LICENSE file.
 */

package com.gemstone.gemfire.internal.concurrent;

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

/**
 * This class is similar to HashSet supporting all the feature of
 * ConcurrentHashMap
 * 
 * @author soubhikc
 */
public class ConcurrentHashSet extends AbstractSet implements
    Set, Serializable {

  private static final long serialVersionUID = -3338819662572203596L;

  private final ConcurrentHashMap map;

  // Dummy value to associate with an Object in the backing Map
  private static final Object PRESENT = new Object();

  public ConcurrentHashSet() {
    map = new ConcurrentHashMap();
  }

  public ConcurrentHashSet(int initialCapacity) {
    map = new ConcurrentHashMap(initialCapacity);
  }

  public ConcurrentHashSet(int initialCapacity, float loadFactor,
      int concurrencyLevel) {
    map = new ConcurrentHashMap(initialCapacity, loadFactor,
        concurrencyLevel);
  }

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

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

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

  @Override
  public boolean isEmpty() {
    return map.isEmpty();
  }

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

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

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