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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.functor.core.algorithm;
18  
19  import java.io.Serializable;
20  import java.util.Iterator;
21  
22  import org.apache.commons.functor.BinaryProcedure;
23  import org.apache.commons.functor.UnaryPredicate;
24  import org.apache.commons.functor.core.composite.UnaryNot;
25  
26  /**
27   * Retain elements in left Iterator that match right UnaryPredicate.
28   *
29   * @version $Revision: 1166328 $ $Date: 2011-09-07 21:32:26 +0200 (Wed, 07 Sep 2011) $
30   */
31  public final class RetainMatching<T>
32      implements BinaryProcedure<Iterator<? extends T>, UnaryPredicate<? super T>>, Serializable {
33      /**
34       * serialVersionUID declaration.
35       */
36      private static final long serialVersionUID = 6760018011875465469L;
37  
38      private static final RetainMatching<Object> INSTANCE = new RetainMatching<Object>();
39  
40      private RemoveMatching<T> removeMatching = new RemoveMatching<T>();
41  
42      /**
43       * {@inheritDoc}
44       * @param left {@link Iterator}
45       * @param right {@link UnaryPredicate}
46       */
47      public void run(Iterator<? extends T> left, UnaryPredicate<? super T> right) {
48          removeMatching.run(left, UnaryNot.not(right));
49      }
50  
51      /**
52       * {@inheritDoc}
53       */
54      public boolean equals(Object obj) {
55          return obj == this || obj != null && obj.getClass().equals(getClass());
56      }
57  
58      /**
59       * {@inheritDoc}
60       */
61      public int hashCode() {
62          return System.identityHashCode(INSTANCE);
63      }
64  
65      /**
66       * Get a static {@link RetainMatching} instance.
67       * @return {@link RetainMatching}
68       */
69      public static RetainMatching<Object> instance() {
70          return INSTANCE;
71      }
72  }