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1   /*
2    *  Copyright 2001-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  package net.sf.collections15.functors.predicate;
17  
18  import net.sf.collections15.Predicate;
19  
20  import java.util.Collection;
21  
22  /***
23   * <code>Predicate</code> implementation that returns <code>true</code> if
24   * exactly one decorated <code>Predicate</code>s return <code>true</code>.
25   *
26   * @author Stephen Colebourne
27   * @author Chris Lambrou (port to Java 5.0)
28   * @since Collections15 1.0
29   */
30  public final class OnePredicate <E> extends AbstractMultplePredicateDecorator<E>
31  {
32  
33      static final long serialVersionUID = 6474539966282189151L;
34  
35      /***
36       * Returns an instance that wraps the specified collection of
37       * <code>Predicate</code>s.
38       *
39       * @param predicates The <cod>Predicate</code>s to wrap. The contents of the
40       *                   collection are defensively copied by the new instance.
41       *
42       * @return A <code>Predicate</code> instance that will only evaluate to
43       *         <code>true</code> if exactly one of the wrapped
44       *         <code>Predicate</code>s evaluates to <code>true</code>.
45       *
46       * @throws IllegalArgumentException Thrown if the collection, or any of its
47       *                                  elements are <code>null</code>. The
48       *                                  collection may be empty, however, in
49       *                                  which case the resulting <code>AnyPredicate</code>
50       *                                  will always return <code>false</code>.
51       */
52      public static <T> OnePredicate<T> getInstance(Collection<Predicate<? super T>> predicates)
53      {
54          return new OnePredicate<T>(predicates);
55      }
56  
57      /***
58       * Creates a new instance that wraps the specified collection of
59       * <code>Predicate</code>s.
60       *
61       * @param predicates The <cod>Predicate</code>s to wrap. The contents of the
62       *                   collection are defensively copied by the new instance.
63       *
64       * @throws IllegalArgumentException Thrown if the collection, or any of its
65       *                                  elements are <code>null</code>. The
66       *                                  collection may be empty, however, in
67       *                                  which case the resulting <code>AnyPredicate</code>
68       *                                  will always return <code>false</code>.
69       */
70      protected OnePredicate(Collection<Predicate<? super E>> predicates)
71      {
72          super(predicates);
73      }
74  
75      /***
76       * Evaluates the <code>Predicate</code> returning <code>true</code> exactly
77       * one of the decorated <code>Predicate</code>s returns <code>true</code>.
78       *
79       * @param object The input object to evaluate.
80       *
81       * @return <code>true</code> if exactly one of the decorated
82       *         <code>Predicate</code>s returns <code>true</code>.
83       */
84      public boolean evaluate(E object)
85      {
86          boolean match = false;
87          int size = decoratedPredicates.size();
88          for (int i = 0; i < size; i++) {
89              if (decoratedPredicates.get(i).evaluate(object)) {
90                  if (match) {
91                      return false;
92                  }
93                  match = true;
94              }
95          }
96          return match;
97      }
98  
99  }