1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.mina.util;
21
22 import java.util.Collection;
23 import java.util.Set;
24 import java.util.concurrent.ConcurrentHashMap;
25 import java.util.concurrent.ConcurrentMap;
26
27 /**
28 * A {@link ConcurrentHashMap}-backed {@link Set}.
29 *
30 * @author The Apache MINA Project (dev@mina.apache.org)
31 * @version $Rev: 597692 $, $Date: 2007-11-23 16:56:32 +0100 (ven, 23 nov 2007) $
32 */
33 public class ConcurrentHashSet<E> extends MapBackedSet<E> {
34
35 private static final long serialVersionUID = 8518578988740277828L;
36
37 public ConcurrentHashSet() {
38 super(new ConcurrentHashMap<E, Boolean>());
39 }
40
41 public ConcurrentHashSet(Collection<E> c) {
42 super(new ConcurrentHashMap<E, Boolean>(), c);
43 }
44
45 @Override
46 public boolean add(E o) {
47 Boolean answer = ((ConcurrentMap<E, Boolean>) map).putIfAbsent(o, Boolean.TRUE);
48 return answer == null;
49 }
50 }