1 /*
2 * Copyright 2009 Red Hat, Inc.
3 *
4 * Red Hat licenses this file to you under the Apache License, version 2.0
5 * (the "License"); you may not use this file except in compliance with the
6 * 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 org.jboss.netty.util;
17
18 import java.io.Serializable;
19 import java.util.AbstractSet;
20 import java.util.Iterator;
21 import java.util.Map;
22 import java.util.Set;
23
24 /**
25 * A {@link Map}-backed {@link Set}.
26 *
27 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
28 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
29 *
30 * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
31 */
32 final class MapBackedSet<E> extends AbstractSet<E> implements Serializable {
33
34 private static final long serialVersionUID = -6761513279741915432L;
35
36 private final Map<E, Boolean> map;
37
38 /**
39 * Creates a new instance which wraps the specified {@code map}.
40 */
41 MapBackedSet(Map<E, Boolean> map) {
42 this.map = map;
43 }
44
45 @Override
46 public int size() {
47 return map.size();
48 }
49
50 @Override
51 public boolean contains(Object o) {
52 return map.containsKey(o);
53 }
54
55 @Override
56 public boolean add(E o) {
57 return map.put(o, Boolean.TRUE) == null;
58 }
59
60 @Override
61 public boolean remove(Object o) {
62 return map.remove(o) != null;
63 }
64
65 @Override
66 public void clear() {
67 map.clear();
68 }
69
70 @Override
71 public Iterator<E> iterator() {
72 return map.keySet().iterator();
73 }
74 }