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.composite;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.functor.Predicate;
022
023 /**
024 * {@link #test Tests} to the logical inverse
025 * of some other predicate.
026 * <p>
027 * Note that although this class implements
028 * {@link Serializable}, a given instance will
029 * only be truly <code>Serializable</code> if the
030 * underlying functor is. Attempts to serialize
031 * an instance whose delegate is not
032 * <code>Serializable</code> will result in an exception.
033 * </p>
034 * @version $Revision: 1156320 $ $Date: 2011-08-10 21:14:50 +0200 (Wed, 10 Aug 2011) $
035 * @author Rodney Waldhoff
036 */
037 public final class Not implements Predicate, Serializable {
038
039 /**
040 * serialVersionUID declaration.
041 */
042 private static final long serialVersionUID = 8268713706856765874L;
043 // attributes
044 // ------------------------------------------------------------------------
045 private final Predicate predicate;
046
047 // constructor
048 // ------------------------------------------------------------------------
049 /**
050 * Create a new Not.
051 * @param predicate Predicate to negate
052 */
053 public Not(Predicate predicate) {
054 if (predicate == null) {
055 throw new IllegalArgumentException("Predicate argument was null");
056 }
057 this.predicate = predicate;
058 }
059
060 // predicate interface
061 // ------------------------------------------------------------------------
062 /**
063 * {@inheritDoc}
064 */
065 public boolean test() {
066 return !(predicate.test());
067 }
068
069 /**
070 * {@inheritDoc}
071 */
072 public boolean equals(Object that) {
073 return that == this || (that instanceof Not && equals((Not) that));
074 }
075
076 /**
077 * Learn whether another Not is equal to this.
078 * @param that the Not to test
079 * @return boolean
080 */
081 public boolean equals(Not 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 = "Not".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 "Not<" + predicate + ">";
101 }
102
103 // static
104 // ------------------------------------------------------------------------
105 /**
106 * Get a Not instance for <code>that</code>.
107 * @param that Predicate to negate
108 * @return Not
109 */
110 public static Predicate not(Predicate that) {
111 return null == that ? null : new Not(that);
112 }
113 }