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 import org.apache.commons.lang3.Validate;
23
24 /**
25 * {@link #test Tests} to the logical inverse
26 * of some other predicate.
27 * <p>
28 * Note that although this class implements
29 * {@link Serializable}, a given instance will
30 * only be truly <code>Serializable</code> if the
31 * underlying functor is. Attempts to serialize
32 * an instance whose delegate is not
33 * <code>Serializable</code> will result in an exception.
34 * </p>
35 * @version $Revision: 1365329 $ $Date: 2012-07-24 19:34:23 -0300 (Tue, 24 Jul 2012) $
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 /**
46 * The adapted predicate has to be negated.
47 */
48 private final Predicate predicate;
49
50 // constructor
51 // ------------------------------------------------------------------------
52 /**
53 * Create a new Not.
54 * @param predicate Predicate to negate
55 */
56 public Not(Predicate predicate) {
57 this.predicate = Validate.notNull(predicate, "Predicate argument was null");
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 @Override
73 public boolean equals(Object that) {
74 return that == this || (that instanceof Not && equals((Not) that));
75 }
76
77 /**
78 * Learn whether another Not is equal to this.
79 * @param that the Not to test
80 * @return boolean
81 */
82 public boolean equals(Not that) {
83 return null != that && predicate.equals(that.predicate);
84 }
85
86 /**
87 * {@inheritDoc}
88 */
89 @Override
90 public int hashCode() {
91 int hash = "Not".hashCode();
92 hash ^= predicate.hashCode();
93 return hash;
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 @Override
100 public String toString() {
101 return "Not<" + predicate + ">";
102 }
103
104 // static
105 // ------------------------------------------------------------------------
106 /**
107 * Get a Not instance for <code>that</code>.
108 * @param that Predicate to negate
109 * @return Not
110 */
111 public static Predicate not(Predicate that) {
112 return null == that ? null : new Not(that);
113 }
114 }