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Java > Open Source Codes > org > apache > commons > collections > functors > NullIsExceptionPredicate


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.collections.functors;
17
18 import java.io.Serializable JavaDoc;
19
20 import org.apache.commons.collections.FunctorException;
21 import org.apache.commons.collections.Predicate;
22
23 /**
24  * Predicate implementation that throws an exception if the input is null.
25  *
26  * @since Commons Collections 3.0
27  * @version $Revision: 1.7 $ $Date: 2004/05/31 16:43:17 $
28  *
29  * @author Stephen Colebourne
30  */
31 public final class NullIsExceptionPredicate implements Predicate, PredicateDecorator, Serializable JavaDoc {
32
33     /** Serial version UID */
34     static final long serialVersionUID = 3243449850504576071L;
35     
36     /** The predicate to decorate */
37     private final Predicate iPredicate;
38     
39     /**
40      * Factory to create the null exception predicate.
41      *
42      * @param predicate the predicate to decorate, not null
43      * @return the predicate
44      * @throws IllegalArgumentException if the predicate is null
45      */
46     public static Predicate getInstance(Predicate predicate) {
47         if (predicate == null) {
48             throw new IllegalArgumentException JavaDoc("Predicate must not be null");
49         }
50         return new NullIsExceptionPredicate(predicate);
51     }
52
53     /**
54      * Constructor that performs no validation.
55      * Use <code>getInstance</code> if you want that.
56      *
57      * @param predicate the predicate to call after the null check
58      */
59     public NullIsExceptionPredicate(Predicate predicate) {
60         super();
61         iPredicate = predicate;
62     }
63
64     /**
65      * Evaluates the predicate returning the result of the decorated predicate
66      * once a null check is performed.
67      *
68      * @param object the input object
69      * @return true if decorated predicate returns true
70      * @throws FunctorException if input is null
71      */
72     public boolean evaluate(Object JavaDoc object) {
73         if (object == null) {
74             throw new FunctorException("Input Object must not be null");
75         }
76         return iPredicate.evaluate(object);
77     }
78
79     /**
80      * Gets the predicate being decorated.
81      *
82      * @return the predicate as the only element in an array
83      * @since Commons Collections 3.1
84      */
85     public Predicate[] getPredicates() {
86         return new Predicate[] {iPredicate};
87     }
88
89 }
90
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