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.collections4.functors;
18
19 import java.io.Serializable;
20 import java.util.Objects;
21
22 import org.apache.commons.collections4.FunctorException;
23 import org.apache.commons.collections4.Predicate;
24 import org.apache.commons.collections4.Transformer;
25
26 /**
27 * Predicate implementation that returns the result of a transformer.
28 *
29 * @param <T> the type of the input to the predicate.
30 * @since 3.0
31 */
32 public final class TransformerPredicate<T> extends AbstractPredicate<T> implements Serializable {
33
34 /** Serial version UID */
35 private static final long serialVersionUID = -2407966402920578741L;
36
37 /**
38 * Creates the predicate.
39 *
40 * @param <T> the type that the predicate queries
41 * @param transformer the transformer to decorate
42 * @return the predicate
43 * @throws NullPointerException if the transformer is null
44 */
45 public static <T> Predicate<T> transformerPredicate(final Transformer<? super T, Boolean> transformer) {
46 return new TransformerPredicate<>(Objects.requireNonNull(transformer, "transformer"));
47 }
48
49 /** The transformer to call */
50 private final Transformer<? super T, Boolean> iTransformer;
51
52 /**
53 * Constructor that performs no validation.
54 * Use {@code transformerPredicate} if you want that.
55 *
56 * @param transformer the transformer to decorate
57 */
58 public TransformerPredicate(final Transformer<? super T, Boolean> transformer) {
59 iTransformer = transformer;
60 }
61
62 /**
63 * Gets the transformer.
64 *
65 * @return the transformer
66 * @since 3.1
67 */
68 public Transformer<? super T, Boolean> getTransformer() {
69 return iTransformer;
70 }
71
72 /**
73 * Evaluates the predicate returning the result of the decorated transformer.
74 *
75 * @param object the input object
76 * @return true if decorated transformer returns Boolean.TRUE
77 * @throws FunctorException if the transformer returns an invalid type
78 */
79 @Override
80 public boolean test(final T object) {
81 final Boolean result = iTransformer.apply(object);
82 if (result == null) {
83 throw new FunctorException(
84 "Transformer must return an instanceof Boolean, it was a null object");
85 }
86 return result.booleanValue();
87 }
88
89 }