001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.functor.core.comparator;
018
019 import java.io.Serializable;
020 import java.util.Comparator;
021
022 import org.apache.commons.functor.BinaryPredicate;
023 import org.apache.commons.functor.UnaryPredicate;
024 import org.apache.commons.functor.adapter.RightBoundPredicate;
025
026 /**
027 * A {@link BinaryPredicate BinaryPredicate} that {@link #test tests}
028 * <code>true</code> iff the left argument is greater than the
029 * right argument under the specified {@link Comparator}.
030 * When no (or a <code>null</code> <code>Comparator</code> is specified,
031 * a {@link Comparable Comparable} <code>Comparator</code> is used.
032 *
033 * @version $Revision: 1166341 $ $Date: 2011-09-07 21:45:19 +0200 (Wed, 07 Sep 2011) $
034 * @author Rodney Waldhoff
035 */
036 public final class IsGreaterThan<T> implements BinaryPredicate<T, T>, Serializable {
037
038 /**
039 * Basic IsGreaterThan instance.
040 */
041 public static final IsGreaterThan<Comparable<?>> INSTANCE = IsGreaterThan.<Comparable<?>>instance();
042
043 /**
044 * serialVersionUID declaration.
045 */
046 private static final long serialVersionUID = -8592932496891910273L;
047
048 private final Comparator<? super T> comparator;
049
050 /**
051 * Construct a <code>IsGreaterThan</code> {@link BinaryPredicate predicate}
052 * for {@link Comparable Comparable}s.
053 */
054 @SuppressWarnings("unchecked")
055 public IsGreaterThan() {
056 this(ComparableComparator.INSTANCE);
057 }
058
059 /**
060 * Construct a <code>IsGreaterThan</code> {@link BinaryPredicate predicate}
061 * for the given {@link Comparator Comparator}.
062 *
063 * @param comparator the {@link Comparator Comparator}, when <code>null</code>,
064 * a <code>Comparator</code> for {@link Comparable Comparable}s will
065 * be used.
066 */
067 public IsGreaterThan(Comparator<? super T> comparator) {
068 if (comparator == null) {
069 throw new IllegalArgumentException("Comparator argument must not be null");
070 }
071 this.comparator = comparator;
072 }
073
074 /**
075 * Return <code>true</code> iff the <i>left</i> parameter is
076 * greater than the <i>right</i> parameter under my current
077 * {@link Comparator Comparator}.
078 * {@inheritDoc}
079 */
080 public boolean test(T left, T right) {
081 return comparator.compare(left, right) > 0;
082 }
083
084 /**
085 * {@inheritDoc}
086 */
087 public boolean equals(Object that) {
088 return that == this || (that instanceof IsGreaterThan<?> && equals((IsGreaterThan<?>) that));
089 }
090
091 /**
092 * Learn whether a given IsGreaterThan is equal to this.
093 * @param that the IsGreaterThan to test
094 * @return boolean
095 */
096 public boolean equals(IsGreaterThan<?> that) {
097 if (null != that) {
098 if (null == comparator) {
099 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 = "IsGreaterThan".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 "IsGreaterThan<" + comparator + ">";
121 }
122
123 /**
124 * Get a typed IsGreaterThan instance.
125 * @param <T>
126 * @return IsGreaterThan<T>
127 */
128 public static <T extends Comparable<?>> IsGreaterThan<T> instance() {
129 return new IsGreaterThan<T>();
130 }
131
132 /**
133 * Get an IsGreaterThan UnaryPredicate.
134 * @param right the right side object of the IsGreaterThan comparison
135 * @return UnaryPredicate<T>
136 */
137 public static <T extends Comparable<?>> UnaryPredicate<T> instance(T right) {
138 return RightBoundPredicate.bind(new IsGreaterThan<T>(), right);
139 }
140
141 }