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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.util.AbstractSet;
    23  import java.util.Collection;
    24  import java.util.IdentityHashMap;
    25  import java.util.Iterator;
    26  import java.util.Map;
    27  import java.util.Set;
    28
    29  /**
    30   * An {@link IdentityHashMap}-backed {@link Set}.
    31   *
    32   * @author The Apache Directory Project (mina-dev@directory.apache.org)
    33   * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (Fri, 13 Jul 2007) $
    34   */
    35  public class IdentityHashSet<E> extends AbstractSet<E> {
    36      private final Map<E, Boolean> delegate = new IdentityHashMap<E, Boolean>();
    37
    38      public IdentityHashSet() {
    39      }
    40
    41      public IdentityHashSet(Collection<E> c) {
    42          addAll(c);
    43      }
    44
    45      @Override
    46      public int size() {
    47          return delegate.size();
    48      }
    49
    50      @Override
    51      public boolean contains(Object o) {
    52          //noinspection SuspiciousMethodCalls
    53          return delegate.containsKey(o);
    54      }
    55
    56      @Override
    57      public Iterator<E> iterator() {
    58          return delegate.keySet().iterator();
    59      }
    60
    61      @Override
    62      public boolean add(E arg0) {
    63          return delegate.put(arg0, Boolean.TRUE) == null;
    64      }
    65
    66      @Override
    67      public boolean remove(Object o) {
    68          //noinspection SuspiciousMethodCalls
    69          return delegate.remove(o) != null;
    70      }
    71
    72      @Override
    73      public void clear() {
    74          delegate.clear();
    75      }
    76  }