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