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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.util.AbstractSet;
23  import java.util.Collection;
24  import java.util.IdentityHashMap;
25  import java.util.Iterator;
26  import java.util.Map;
27  import java.util.Set;
28  
29  /**
30   * An {@link IdentityHashMap}-backed {@link Set}.
31   *
32   * @author The Apache Directory Project (mina-dev@directory.apache.org)
33   * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (Fri, 13 Jul 2007) $
34   */
35  public class IdentityHashSet<E> extends AbstractSet<E> {
36      private final Map<E, Boolean> delegate = new IdentityHashMap<E, Boolean>();
37  
38      public IdentityHashSet() {
39      }
40  
41      public IdentityHashSet(Collection<E> c) {
42          addAll(c);
43      }
44  
45      @Override
46      public int size() {
47          return delegate.size();
48      }
49  
50      @Override
51      public boolean contains(Object o) {
52          //noinspection SuspiciousMethodCalls
53          return delegate.containsKey(o);
54      }
55  
56      @Override
57      public Iterator<E> iterator() {
58          return delegate.keySet().iterator();
59      }
60  
61      @Override
62      public boolean add(E arg0) {
63          return delegate.put(arg0, Boolean.TRUE) == null;
64      }
65  
66      @Override
67      public boolean remove(Object o) {
68          //noinspection SuspiciousMethodCalls
69          return delegate.remove(o) != null;
70      }
71  
72      @Override
73      public void clear() {
74          delegate.clear();
75      }
76  }