1 package org.apache.lucene.util;
4 * Licensed to the Apache Software Foundation (ASF) under one or more
5 * contributor license agreements. See the NOTICE file distributed with
6 * this work for additional information regarding copyright ownership.
7 * The ASF licenses this file to You under the Apache License, Version 2.0
8 * (the "License"); you may not use this file except in compliance with
9 * the License. You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
20 import java.io.Serializable;
21 import java.util.AbstractSet;
22 import java.util.Iterator;
26 * A Set implementation that wraps an actual Map based
31 public final class MapBackedSet<E> extends AbstractSet<E> implements Serializable {
33 private static final long serialVersionUID = -6761513279741915432L;
35 private final Map<E, Boolean> map;
38 * Creates a new instance which wraps the specified {@code map}.
40 public MapBackedSet(Map<E, Boolean> map) {
50 public boolean contains(Object o) {
51 return map.containsKey(o);
55 public boolean add(E o) {
56 return map.put(o, Boolean.TRUE) == null;
60 public boolean remove(Object o) {
61 return map.remove(o) != null;
70 public Iterator<E> iterator() {
71 return map.keySet().iterator();