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 import org.apache.commons.collections.Transformer;
23
24 /**
25 * Transformer implementation that calls a Predicate using the input object
26 * and then returns the result.
27 *
28 * @since 3.0
29 * @version $Id: PredicateTransformer.java 1435965 2013-01-20 21:13:18Z tn $
30 */
31 public class PredicateTransformer<T> implements Transformer<T, Boolean>, Serializable {
32
33 /** Serial version UID */
34 private static final long serialVersionUID = 5278818408044349346L;
35
36 /** The closure to wrap */
37 private final Predicate<? super T> iPredicate;
38
39 /**
40 * Factory method that performs validation.
41 *
42 * @param <T> the input type
43 * @param predicate the predicate to call, not null
44 * @return the <code>predicate</code> transformer
45 * @throws IllegalArgumentException if the predicate is null
46 */
47 public static <T> Transformer<T, Boolean> predicateTransformer(final Predicate<? super T> predicate) {
48 if (predicate == null) {
49 throw new IllegalArgumentException("Predicate must not be null");
50 }
51 return new PredicateTransformer<T>(predicate);
52 }
53
54 /**
55 * Constructor that performs no validation.
56 * Use <code>getInstance</code> if you want that.
57 *
58 * @param predicate the predicate to call, not null
59 */
60 public PredicateTransformer(final Predicate<? super T> predicate) {
61 super();
62 iPredicate = predicate;
63 }
64
65 /**
66 * Transforms the input to result by calling a predicate.
67 *
68 * @param input the input object to transform
69 * @return the transformed result
70 */
71 public Boolean transform(final T input) {
72 return Boolean.valueOf(iPredicate.evaluate(input));
73 }
74
75 /**
76 * Gets the predicate.
77 *
78 * @return the predicate
79 * @since 3.1
80 */
81 public Predicate<? super T> getPredicate() {
82 return iPredicate;
83 }
84
85 }