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;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.functor.BinaryPredicate;
022 import org.apache.commons.functor.UnaryPredicate;
023 import org.apache.commons.functor.adapter.RightBoundPredicate;
024
025 /**
026 * {@link #test Tests}
027 * <code>true</code> iff its arguments are
028 * {@link Object#equals equal} or both
029 * <code>null</code>.
030 * <p>
031 * This relation is
032 * an equivalence relation on
033 * the set of objects that adhere to the
034 * <code>Object.equals</code> contract.
035 * </p>
036 *
037 * @param <L> the left argument type.
038 * @param <R> the right argument type.
039 * @version $Revision: 1160389 $ $Date: 2011-08-22 21:31:15 +0200 (Mon, 22 Aug 2011) $
040 * @author Rodney Waldhoff
041 */
042 public final class IsEqual<L, R> implements BinaryPredicate<L, R>, Serializable {
043 // static attributes
044 // ------------------------------------------------------------------------
045 /**
046 * Basic IsEqual<Object, Object> instance.
047 */
048 public static final IsEqual<Object, Object> INSTANCE = IsEqual.<Object, Object>instance();
049 /**
050 * serialVersionUID declaration.
051 */
052 private static final long serialVersionUID = -6777016236280121159L;
053
054 // constructor
055 // ------------------------------------------------------------------------
056 /**
057 * Create a new IsEqual.
058 */
059 public IsEqual() {
060 }
061
062 // predicate interface
063 // ------------------------------------------------------------------------
064 /**
065 * {@inheritDoc}
066 */
067 public boolean test(L left, R right) {
068 return left == right || left != null && left.equals(right);
069 }
070
071 /**
072 * {@inheritDoc}
073 */
074 public boolean equals(Object that) {
075 return that instanceof IsEqual<?, ?>;
076 }
077
078 /**
079 * {@inheritDoc}
080 */
081 public int hashCode() {
082 return "IsEqual".hashCode();
083 }
084
085 /**
086 * {@inheritDoc}
087 */
088 public String toString() {
089 return "IsEqual";
090 }
091
092 // static methods
093 // ------------------------------------------------------------------------
094 /**
095 * Get an IsEqual instance.
096 * @param <L> the left argument type.
097 * @param <R> the right argument type.
098 * @return IsEqual
099 */
100 public static <L, R> IsEqual<L, R> instance() {
101 return new IsEqual<L, R>();
102 }
103
104 /**
105 * Get an IsEqual UnaryPredicate.
106 * @param <L> the left argument type.
107 * @param <R> the right argument type.
108 * @param object bound comparison object
109 * @return UnaryPredicate<L>
110 */
111 public static <L, R> UnaryPredicate<L> to(R object) {
112 return new RightBoundPredicate<L>(new IsEqual<L, R>(), object);
113 }
114 }