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.collections.functors;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.collections.Predicate;
22
23 /**
24 * Predicate implementation that returns the opposite of the decorated predicate.
25 *
26 * @since 3.0
27 * @version $Id: NotPredicate.java 1429905 2013-01-07 17:15:14Z ggregory $
28 */
29 public final class NotPredicate<T> implements Predicate<T>, PredicateDecorator<T>, Serializable {
30
31 /** Serial version UID */
32 private static final long serialVersionUID = -2654603322338049674L;
33
34 /** The predicate to decorate */
35 private final Predicate<? super T> iPredicate;
36
37 /**
38 * Factory to create the not predicate.
39 *
40 * @param <T> the type that the predicate queries
41 * @param predicate the predicate to decorate, not null
42 * @return the predicate
43 * @throws IllegalArgumentException if the predicate is null
44 */
45 public static <T> Predicate<T> notPredicate(final Predicate<? super T> predicate) {
46 if (predicate == null) {
47 throw new IllegalArgumentException("Predicate must not be null");
48 }
49 return new NotPredicate<T>(predicate);
50 }
51
52 /**
53 * Constructor that performs no validation.
54 * Use <code>getInstance</code> if you want that.
55 *
56 * @param predicate the predicate to call after the null check
57 */
58 public NotPredicate(final Predicate<? super T> predicate) {
59 super();
60 iPredicate = predicate;
61 }
62
63 /**
64 * Evaluates the predicate returning the opposite to the stored predicate.
65 *
66 * @param object the input object
67 * @return true if predicate returns false
68 */
69 public boolean evaluate(final T object) {
70 return !iPredicate.evaluate(object);
71 }
72
73 /**
74 * Gets the predicate being decorated.
75 *
76 * @return the predicate as the only element in an array
77 * @since 3.1
78 */
79 @SuppressWarnings("unchecked")
80 public Predicate<? super T>[] getPredicates() {
81 return new Predicate[] {iPredicate};
82 }
83
84 }