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 }