//
   //  ========================================================================
   //  Copyright (c) 1995-2013 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.util;
  
  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;
  
  public class ConcurrentHashSet<E> extends AbstractSet<E> implements Set<E>
  {
      private final Map<E, Boolean> _map = new ConcurrentHashMap<E, Boolean>();
      private transient Set<E> _keys = _map.keySet();
  
      public ConcurrentHashSet()
      {
      }
  
      @Override
      public boolean add(E e)
      {
          return _map.put(e,Boolean.TRUE) == null;
      }
  
      @Override
      public void clear()
      {
          _map.clear();
      }
  
      @Override
      public boolean contains(Object o)
      {
          return _map.containsKey(o);
      }
  
      @Override
      public boolean containsAll(Collection<?> c)
      {
          return _keys.containsAll(c);
      }
  
      @Override
      public boolean equals(Object o)
      {
          return o == this || _keys.equals(o);
      }
  
      @Override
      public int hashCode()
      {
          return _keys.hashCode();
      }
  
      @Override
      public boolean isEmpty()
      {
          return _map.isEmpty();
      }
  
      @Override
      public Iterator<E> iterator()
      {
          return _keys.iterator();
      }
  
      @Override
      public boolean remove(Object o)
      {
          return _map.remove(o) != null;
      }
  
      @Override
      public boolean removeAll(Collection<?> c)
      {
          return _keys.removeAll(c);
      }
  
      @Override
      public boolean retainAll(Collection<?> c)
      {
         return _keys.retainAll(c);
     }
 
     @Override
     public int size()
     {
         return _map.size();
     }
 
     @Override
     public Object[] toArray()
     {
         return _keys.toArray();
     }
 
     @Override
     public <T> T[] toArray(T[] a)
     {
         return _keys.toArray(a);
     }
 
     @Override
     public String toString()
     {
         return _keys.toString();
     }
 }