1 /*
2 * Copyright 2012 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 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 final class MapBackedSet<E> extends AbstractSet<E> implements Serializable {
28
29 private static final long serialVersionUID = -6761513279741915432L;
30
31 private final Map<E, Boolean> map;
32
33 /**
34 * Creates a new instance which wraps the specified {@code map}.
35 */
36 MapBackedSet(Map<E, Boolean> map) {
37 this.map = map;
38 }
39
40 @Override
41 public int size() {
42 return map.size();
43 }
44
45 @Override
46 public boolean contains(Object o) {
47 return map.containsKey(o);
48 }
49
50 @Override
51 public boolean add(E o) {
52 return map.put(o, Boolean.TRUE) == null;
53 }
54
55 @Override
56 public boolean remove(Object o) {
57 return map.remove(o) != null;
58 }
59
60 @Override
61 public void clear() {
62 map.clear();
63 }
64
65 @Override
66 public Iterator<E> iterator() {
67 return map.keySet().iterator();
68 }
69 }