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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.comparator;
18  
19  import java.io.Serializable;
20  import java.util.Comparator;
21  
22  import org.apache.commons.functor.BinaryPredicate;
23  import org.apache.commons.functor.UnaryPredicate;
24  import org.apache.commons.functor.adapter.RightBoundPredicate;
25  
26  /**
27   * A {@link BinaryPredicate BinaryPredicate} that {@link #test tests}
28   * <code>true</code> iff the left argument is less than or equal to the
29   * right argument under the specified {@link Comparator}.
30   * When no (or a <code>null</code> <code>Comparator</code> is specified,
31   * a {@link Comparable Comparable} <code>Comparator</code> is used.
32   *
33   * @version $Revision: 1166346 $ $Date: 2011-09-07 21:48:07 +0200 (Wed, 07 Sep 2011) $
34   * @author Rodney Waldhoff
35   */
36  public final class IsLessThanOrEqual<T> implements BinaryPredicate<T, T>, Serializable {
37  
38      /**
39       * Basic IsLessThanOrEqual instance.
40       */
41      public static final IsLessThanOrEqual<Comparable<?>> INSTANCE = IsLessThanOrEqual.<Comparable<?>>instance();
42  
43      /**
44       * serialVersionUID declaration.
45       */
46      private static final long serialVersionUID = -7270189005780457145L;
47  
48      private final Comparator<? super T> comparator;
49  
50      /**
51       * Construct a <code>IsLessThanOrEqual</code> {@link BinaryPredicate predicate}
52       * for {@link Comparable Comparable}s.
53       */
54      @SuppressWarnings("unchecked")
55      public IsLessThanOrEqual() {
56          this(ComparableComparator.INSTANCE);
57      }
58  
59      /**
60       * Construct a <code>IsLessThanOrEqual</code> {@link BinaryPredicate predicate}
61       * for the given {@link Comparator Comparator}.
62       *
63       * @param comparator the {@link Comparator Comparator}, when <code>null</code>,
64       *        a <code>Comparator</code> for {@link Comparable Comparable}s will
65       *        be used.
66       */
67      public IsLessThanOrEqual(Comparator<? super T> comparator) {
68          if (comparator == null) {
69              throw new IllegalArgumentException("Comparator argument must not be null");
70          }
71          this.comparator = comparator;
72      }
73  
74      /**
75       * {@inheritDoc}
76       * Return <code>true</code> iff the <i>left</i> parameter is
77       * less than or equal to the <i>right</i> parameter under my current
78       * {@link Comparator Comparator}.
79       */
80      public boolean test(T left, T right) {
81          return comparator.compare(left, right) <= 0;
82      }
83  
84      /**
85       * {@inheritDoc}
86       */
87      public boolean equals(Object that) {
88          return that == this || (that instanceof IsLessThanOrEqual<?> && equals((IsLessThanOrEqual<?>) that));
89      }
90  
91      /**
92       * Learn whether another IsLessThanOrEqual is equal to this.
93       * @param that the IsLessThanOrEqual to test.
94       * @return boolean
95       */
96      public boolean equals(IsLessThanOrEqual<?> that) {
97          if (null != that) {
98              if (null == comparator) {
99                  return null == that.comparator;
100             }
101             return comparator.equals(that.comparator);
102         }
103         return false;
104     }
105 
106     /**
107      * {@inheritDoc}
108      */
109     public int hashCode() {
110         int hash = "IsLessThanOrEqual".hashCode();
111         // by construction, comparator is never null
112         hash ^= comparator.hashCode();
113         return hash;
114     }
115 
116     /**
117      * {@inheritDoc}
118      */
119     public String toString() {
120         return "IsLessThanOrEqual<" + comparator + ">";
121     }
122 
123     /**
124      * Get a typed IsLessThanOrEqual instance.
125      * @param <T>
126      * @return IsLessThanOrEqual<T>
127      */
128     public static <T extends Comparable<?>> IsLessThanOrEqual<T> instance() {
129         return new IsLessThanOrEqual<T>();
130     }
131 
132     /**
133      * Get an IsLessThanOrEqual UnaryPredicate.
134      * @param right the right side object of the comparison.
135      * @return UnaryPredicate
136      */
137     public static <T extends Comparable<?>> UnaryPredicate<T> instance(T right) {
138         return RightBoundPredicate.bind(new IsLessThanOrEqual<T>(), right);
139     }
140 
141 }