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.adapter;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.functor.BinaryFunction;
022 import org.apache.commons.functor.BinaryPredicate;
023
024 /**
025 * Adapts a
026 * {@link BinaryPredicate BinaryPredicate}
027 * to the
028 * {@link BinaryFunction BinaryFunction} interface.
029 * <p/>
030 * Note that although this class implements
031 * {@link Serializable}, a given instance will
032 * only be truly <code>Serializable</code> if the
033 * underlying predicate is. Attempts to serialize
034 * an instance whose delegate is not
035 * <code>Serializable</code> will result in an exception.
036 *
037 * @param <L> the left argument type.
038 * @param <R> the right argument type.
039 * @version $Revision: 1156767 $ $Date: 2011-08-11 21:38:12 +0200 (Thu, 11 Aug 2011) $
040 * @author Rodney Waldhoff
041 */
042 public final class BinaryPredicateBinaryFunction<L, R> implements BinaryFunction<L, R, Boolean>, Serializable {
043 /**
044 * serialVersionUID declaration.
045 */
046 private static final long serialVersionUID = 207209665276797678L;
047 /** The {@link BinaryPredicate BinaryPredicate} I'm wrapping. */
048 private final BinaryPredicate<? super L, ? super R> predicate;
049
050 /**
051 * Create a new BinaryPredicateBinaryFunction.
052 * @param predicate to adapt
053 */
054 public BinaryPredicateBinaryFunction(BinaryPredicate<? super L, ? super R> predicate) {
055 this.predicate = predicate;
056 }
057
058 /**
059 * {@inheritDoc}
060 * Returns <code>Boolean.TRUE</code> (<code>Boolean.FALSE</code>)
061 * when the {@link BinaryPredicate#test test} method of my underlying
062 * predicate returns <code>true</code> (<code>false</code>).
063 *
064 * @return a non-<code>null</code> <code>Boolean</code> instance
065 */
066 public Boolean evaluate(L left, R right) {
067 return predicate.test(left, right) ? Boolean.TRUE : Boolean.FALSE;
068 }
069
070 /**
071 * {@inheritDoc}
072 */
073 public boolean equals(Object that) {
074 return that == this
075 || (that instanceof BinaryPredicateBinaryFunction<?, ?>
076 && equals((BinaryPredicateBinaryFunction<?, ?>) that));
077 }
078
079 /**
080 * Learn whether another BinaryPredicateBinaryFunction is equal to this.
081 * @param that BinaryPredicateBinaryFunction to test
082 * @return boolean
083 */
084 public boolean equals(BinaryPredicateBinaryFunction<?, ?> that) {
085 return null != that && (null == predicate ? null == that.predicate : predicate.equals(that.predicate));
086 }
087
088 /**
089 * {@inheritDoc}
090 */
091 public int hashCode() {
092 int hash = "BinaryPredicateBinaryFunction".hashCode();
093 if (null != predicate) {
094 hash ^= predicate.hashCode();
095 }
096 return hash;
097 }
098
099 /**
100 * {@inheritDoc}
101 */
102 public String toString() {
103 return "BinaryPredicateBinaryFunction<" + predicate + ">";
104 }
105
106 /**
107 * Adapt the given, possibly-<code>null</code>,
108 * {@link BinaryPredicate BinaryPredicate} to the
109 * {@link BinaryFunction BinaryFunction} interface.
110 * When the given <code>BinaryPredicate</code> is <code>null</code>,
111 * returns <code>null</code>.
112 *
113 * @param <L> left type
114 * @param <R> right type
115 * @param predicate the possibly-<code>null</code>
116 * {@link BinaryPredicate BinaryPredicate} to adapt
117 * @return a <code>BinaryPredicateBinaryFunction</code> wrapping the given
118 * {@link BinaryPredicate BinaryPredicate}, or <code>null</code>
119 * if the given <code>BinaryPredicate</code> is <code>null</code>
120 */
121 public static <L, R> BinaryPredicateBinaryFunction<L, R> adapt(BinaryPredicate<? super L, ? super R> predicate) {
122 return null == predicate ? null : new BinaryPredicateBinaryFunction<L, R>(predicate);
123 }
124
125 }