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.Predicate;
022 import org.apache.commons.functor.UnaryPredicate;
023
024 /**
025 * Adapts a
026 * {@link Predicate Predicate}
027 * to the
028 * {@link UnaryPredicate UnaryPredicate} interface
029 * by ignoring the given argument.
030 * <p/>
031 * Note that although this class implements
032 * {@link Serializable}, a given instance will
033 * only be truly <code>Serializable</code> if the
034 * underlying functor is. Attempts to serialize
035 * an instance whose delegate is not
036 * <code>Serializable</code> will result in an exception.
037 *
038 * @param <A> the argument type.
039 * @version $Revision: 1157628 $ $Date: 2011-08-14 22:04:52 +0200 (Sun, 14 Aug 2011) $
040 * @author Rodney Waldhoff
041 */
042 public final class PredicateUnaryPredicate<A> implements UnaryPredicate<A>, Serializable {
043 /**
044 * serialVersionUID declaration.
045 */
046 private static final long serialVersionUID = -5168896606842881702L;
047 /** The {@link Predicate Predicate} I'm wrapping. */
048 private final Predicate predicate;
049
050 /**
051 * Create a new PredicateUnaryPredicate.
052 * @param predicate to adapt
053 */
054 public PredicateUnaryPredicate(Predicate predicate) {
055 if (predicate == null) {
056 throw new IllegalArgumentException("Predicate argument was null");
057 }
058 this.predicate = predicate;
059 }
060
061 /**
062 * {@inheritDoc}
063 */
064 public boolean test(Object obj) {
065 return predicate.test();
066 }
067
068 /**
069 * {@inheritDoc}
070 */
071 public boolean equals(Object that) {
072 return that == this || (that instanceof PredicateUnaryPredicate<?>
073 && equals((PredicateUnaryPredicate<?>) that));
074 }
075
076 /**
077 * Learn whether a given PredicateUnaryPredicate is equal to this.
078 * @param that PredicateUnaryPredicate to test
079 * @return boolean
080 */
081 public boolean equals(PredicateUnaryPredicate<?> that) {
082 return null != that && (null == predicate ? null == that.predicate : predicate.equals(that.predicate));
083 }
084
085 /**
086 * {@inheritDoc}
087 */
088 public int hashCode() {
089 int hash = "PredicateUnaryPredicate".hashCode();
090 if (null != predicate) {
091 hash ^= predicate.hashCode();
092 }
093 return hash;
094 }
095
096 /**
097 * {@inheritDoc}
098 */
099 public String toString() {
100 return "PredicateUnaryPredicate<" + predicate + ">";
101 }
102
103 /**
104 * Adapt a Predicate to the UnaryPredicate interface.
105 * @param <A> the argument type.
106 * @param predicate to adapt
107 * @return PredicateUnaryPredicate<A>
108 */
109 public static <A> PredicateUnaryPredicate<A> adapt(Predicate predicate) {
110 return null == predicate ? null : new PredicateUnaryPredicate<A>(predicate);
111 }
112
113 }