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 */
32 public class ConcurrentHashSet<E> extends MapBackedSet<E> {
33
34 private static final long serialVersionUID = 8518578988740277828L;
35
36 public ConcurrentHashSet() {
37 super(new ConcurrentHashMap<E, Boolean>());
38 }
39
40 public ConcurrentHashSet(Collection<E> c) {
41 super(new ConcurrentHashMap<E, Boolean>(), c);
42 }
43
44 @Override
45 public boolean add(E o) {
46 Boolean answer = ((ConcurrentMap<E, Boolean>) map).putIfAbsent(o, Boolean.TRUE);
47 return answer == null;
48 }
49 }