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    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   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
    33   */
    34  public class MapBackedSet<E> extends AbstractSet<E> implements Serializable {
    35
    36      private static final long serialVersionUID = -8347878570391674042L;
    37
    38      protected final Map<E, Boolean> map;
    39
    40      public MapBackedSet(Map<E, Boolean> map) {
    41          this.map = map;
    42      }
    43
    44      public MapBackedSet(Map<E, Boolean> map, Collection<E> c) {
    45          this.map = map;
    46          addAll(c);
    47      }
    48
    49      @Override
    50      public int size() {
    51          return map.size();
    52      }
    53
    54      @Override
    55      public boolean contains(Object o) {
    56          return map.containsKey(o);
    57      }
    58
    59      @Override
    60      public Iterator<E> iterator() {
    61          return map.keySet().iterator();
    62      }
    63
    64      @Override
    65      public boolean add(E o) {
    66          return map.put(o, Boolean.TRUE) == null;
    67      }
    68
    69      @Override
    70      public boolean remove(Object o) {
    71          return map.remove(o) != null;
    72      }
    73
    74      @Override
    75      public void clear() {
    76          map.clear();
    77      }
    78  }