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 * @param <E> The element stored in the set
33 *
34 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
35 */
36 public class MapBackedSet<E> extends AbstractSet<E> implements Serializable {
37
38 private static final long serialVersionUID = -8347878570391674042L;
39
40 protected final Map<E, Boolean> map;
41
42 /**
43 * Creates a new MapBackedSet instance
44 *
45 * @param map The map that we want to back
46 */
47 public MapBackedSet(Map<E, Boolean> map) {
48 this.map = map;
49 }
50
51 /**
52 * Creates a new MapBackedSet instance
53 *
54 * @param map The map that we want to back
55 * @param c The elements we want to add in the map
56 */
57 public MapBackedSet(Map<E, Boolean> map, Collection<E> c) {
58 this.map = map;
59 addAll(c);
60 }
61
62 /**
63 * {@inheritDoc}
64 */
65 @Override
66 public int size() {
67 return map.size();
68 }
69
70 /**
71 * {@inheritDoc}
72 */
73 @Override
74 public boolean contains(Object o) {
75 return map.containsKey(o);
76 }
77
78 /**
79 * {@inheritDoc}
80 */
81 @Override
82 public Iterator<E> iterator() {
83 return map.keySet().iterator();
84 }
85
86 /**
87 * {@inheritDoc}
88 */
89 @Override
90 public boolean add(E o) {
91 return map.put(o, Boolean.TRUE) == null;
92 }
93
94 /**
95 * {@inheritDoc}
96 */
97 @Override
98 public boolean remove(Object o) {
99 return map.remove(o) != null;
100 }
101
102 /**
103 * {@inheritDoc}
104 */
105 @Override
106 public void clear() {
107 map.clear();
108 }
109 }