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 false if the input is null.
25 *
26 * @since 3.0
27 * @version $Id: NullIsFalsePredicate.java 1429905 2013-01-07 17:15:14Z ggregory $
28 */
29 public final class NullIsFalsePredicate<T> implements Predicate<T>, PredicateDecorator<T>, Serializable {
30
31 /** Serial version UID */
32 private static final long serialVersionUID = -2997501534564735525L;
33
34 /** The predicate to decorate */
35 private final Predicate<? super T> iPredicate;
36
37 /**
38 * Factory to create the null false 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> nullIsFalsePredicate(final Predicate<? super T> predicate) {
46 if (predicate == null) {
47 throw new IllegalArgumentException("Predicate must not be null");
48 }
49 return new NullIsFalsePredicate<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 NullIsFalsePredicate(final Predicate<? super T> predicate) {
59 super();
60 iPredicate = predicate;
61 }
62
63 /**
64 * Evaluates the predicate returning the result of the decorated predicate
65 * once a null check is performed.
66 *
67 * @param object the input object
68 * @return true if decorated predicate returns true, false if input is null
69 */
70 public boolean evaluate(final T object) {
71 if (object == null) {
72 return false;
73 }
74 return iPredicate.evaluate(object);
75 }
76
77 /**
78 * Gets the predicate being decorated.
79 *
80 * @return the predicate as the only element in an array
81 * @since 3.1
82 */
83 @SuppressWarnings("unchecked")
84 public Predicate<? super T>[] getPredicates() {
85 return new Predicate[] { iPredicate };
86 }
87
88 }