01: /*
02: * Licensed to the Apache Software Foundation (ASF) under one
03: * or more contributor license agreements. See the NOTICE file
04: * distributed with this work for additional information
05: * regarding copyright ownership. The ASF licenses this file
06: * to you under the Apache License, Version 2.0 (the
07: * "License"); you may not use this file except in compliance
08: * with the License. You may obtain a copy of the License at
09: *
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 08:56:32 -0700 (Fri, 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(
48: o, Boolean.TRUE);
49: return answer == null;
50: }
51: }
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