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1   /*
2    * Copyright 2013 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.util.internal;
17  
18  import java.io.Serializable;
19  import java.util.AbstractSet;
20  import java.util.Iterator;
21  import java.util.concurrent.ConcurrentMap;
22  
23  public final class ConcurrentSet<E> extends AbstractSet<E> implements Serializable {
24  
25      private static final long serialVersionUID = -6761513279741915432L;
26  
27      private final ConcurrentMap<E, Boolean> map;
28  
29      /**
30       * Creates a new instance which wraps the specified {@code map}.
31       */
32      public ConcurrentSet() {
33          map = PlatformDependent.newConcurrentHashMap();
34      }
35  
36      @Override
37      public int size() {
38          return map.size();
39      }
40  
41      @Override
42      public boolean contains(Object o) {
43          return map.containsKey(o);
44      }
45  
46      @Override
47      public boolean add(E o) {
48          return map.putIfAbsent(o, Boolean.TRUE) == null;
49      }
50  
51      @Override
52      public boolean remove(Object o) {
53          return map.remove(o) != null;
54      }
55  
56      @Override
57      public void clear() {
58          map.clear();
59      }
60  
61      @Override
62      public Iterator<E> iterator() {
63          return map.keySet().iterator();
64      }
65  }