org.hornetq.utils.ConcurrentHashSet Maven / Gradle / Ivy
/*
* Copyright 2009 Red Hat, Inc.
* Red Hat licenses this file to you 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 org.hornetq.utils;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
*
* A ConcurrentHashSet.
*
* Offers same concurrency as ConcurrentHashMap but for a Set
*
* @author Tim Fox
* @version $Revision: 1935 $
*
* $Id: ConcurrentReaderHashSet.java 1935 2007-01-09 23:29:20Z [email protected] $
*/
public class ConcurrentHashSet extends AbstractSet implements ConcurrentSet
{
private final ConcurrentMap theMap;
private static final Object dummy = new Object();
public ConcurrentHashSet()
{
theMap = new ConcurrentHashMap();
}
@Override
public int size()
{
return theMap.size();
}
@Override
public Iterator iterator()
{
return theMap.keySet().iterator();
}
@Override
public boolean isEmpty()
{
return theMap.isEmpty();
}
@Override
public boolean add(final E o)
{
return theMap.put(o, ConcurrentHashSet.dummy) == null;
}
@Override
public boolean contains(final Object o)
{
return theMap.containsKey(o);
}
@Override
public void clear()
{
theMap.clear();
}
@Override
public boolean remove(final Object o)
{
return theMap.remove(o) == ConcurrentHashSet.dummy;
}
public boolean addIfAbsent(final E o)
{
Object obj = theMap.putIfAbsent(o, ConcurrentHashSet.dummy);
return obj == null;
}
}