001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 * 019 */ 020package org.apache.mina.util; 021 022import java.util.Collection; 023import java.util.Set; 024import java.util.concurrent.ConcurrentHashMap; 025import java.util.concurrent.ConcurrentMap; 026 027/** 028 * A {@link ConcurrentHashMap}-backed {@link Set}. 029 * 030 * @author <a href="http://mina.apache.org">Apache MINA Project</a> 031 */ 032public class ConcurrentHashSet<E> extends MapBackedSet<E> { 033 034 private static final long serialVersionUID = 8518578988740277828L; 035 036 public ConcurrentHashSet() { 037 super(new ConcurrentHashMap<E, Boolean>()); 038 } 039 040 public ConcurrentHashSet(Collection<E> c) { 041 super(new ConcurrentHashMap<E, Boolean>(), c); 042 } 043 044 @Override 045 public boolean add(E o) { 046 Boolean answer = ((ConcurrentMap<E, Boolean>) map).putIfAbsent(o, Boolean.TRUE); 047 return answer == null; 048 } 049}