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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.io.Serializable;
23  import java.util.AbstractSet;
24  import java.util.Collection;
25  import java.util.Iterator;
26  import java.util.Map;
27  import java.util.Set;
28  
29  /**
30   * A {@link Map}-backed {@link Set}.
31   *
32   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
33   */
34  public class MapBackedSet<E> extends AbstractSet<E> implements Serializable {
35  
36      private static final long serialVersionUID = -8347878570391674042L;
37  
38      protected final Map<E, Boolean> map;
39  
40      public MapBackedSet(Map<E, Boolean> map) {
41          this.map = map;
42      }
43  
44      public MapBackedSet(Map<E, Boolean> map, Collection<E> c) {
45          this.map = map;
46          addAll(c);
47      }
48  
49      @Override
50      public int size() {
51          return map.size();
52      }
53  
54      @Override
55      public boolean contains(Object o) {
56          return map.containsKey(o);
57      }
58  
59      @Override
60      public Iterator<E> iterator() {
61          return map.keySet().iterator();
62      }
63  
64      @Override
65      public boolean add(E o) {
66          return map.put(o, Boolean.TRUE) == null;
67      }
68  
69      @Override
70      public boolean remove(Object o) {
71          return map.remove(o) != null;
72      }
73  
74      @Override
75      public void clear() {
76          map.clear();
77      }
78  }