1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.functor.core.composite;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.Predicate;
22
23 /**
24 * {@link #test Tests} to the logical inverse
25 * of some other predicate.
26 * <p>
27 * Note that although this class implements
28 * {@link Serializable}, a given instance will
29 * only be truly <code>Serializable</code> if the
30 * underlying functor is. Attempts to serialize
31 * an instance whose delegate is not
32 * <code>Serializable</code> will result in an exception.
33 * </p>
34 * @version $Revision: 1156320 $ $Date: 2011-08-10 21:14:50 +0200 (Wed, 10 Aug 2011) $
35 * @author Rodney Waldhoff
36 */
37 public final class Not implements Predicate, Serializable {
38
39 /**
40 * serialVersionUID declaration.
41 */
42 private static final long serialVersionUID = 8268713706856765874L;
43 // attributes
44 // ------------------------------------------------------------------------
45 private final Predicate predicate;
46
47 // constructor
48 // ------------------------------------------------------------------------
49 /**
50 * Create a new Not.
51 * @param predicate Predicate to negate
52 */
53 public Not(Predicate predicate) {
54 if (predicate == null) {
55 throw new IllegalArgumentException("Predicate argument was null");
56 }
57 this.predicate = predicate;
58 }
59
60 // predicate interface
61 // ------------------------------------------------------------------------
62 /**
63 * {@inheritDoc}
64 */
65 public boolean test() {
66 return !(predicate.test());
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 public boolean equals(Object that) {
73 return that == this || (that instanceof Not && equals((Not) that));
74 }
75
76 /**
77 * Learn whether another Not is equal to this.
78 * @param that the Not to test
79 * @return boolean
80 */
81 public boolean equals(Not that) {
82 return null != that && (null == predicate ? null == that.predicate : predicate.equals(that.predicate));
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 public int hashCode() {
89 int hash = "Not".hashCode();
90 if (null != predicate) {
91 hash ^= predicate.hashCode();
92 }
93 return hash;
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 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 }