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.Factory;
23 import org.apache.commons.collections4.Transformer;
24
25 /**
26 * Transformer implementation that calls a Factory and returns the result.
27 *
28 * @param <T> the type of the input to the function.
29 * @param <R> the type of the result of the function.
30 * @since 3.0
31 */
32 public class FactoryTransformer<T, R> implements Transformer<T, R>, Serializable {
33
34 /** Serial version UID */
35 private static final long serialVersionUID = -6817674502475353160L;
36
37 /**
38 * Factory method that performs validation.
39 *
40 * @param <I> the input type
41 * @param <O> the output type
42 * @param factory the factory to call, not null
43 * @return the {@code factory} transformer
44 * @throws NullPointerException if the factory is null
45 */
46 public static <I, O> Transformer<I, O> factoryTransformer(final Factory<? extends O> factory) {
47 return new FactoryTransformer<>(Objects.requireNonNull(factory, "factory"));
48 }
49
50 /** The factory to wrap */
51 private final Factory<? extends R> iFactory;
52
53 /**
54 * Constructor that performs no validation.
55 * Use {@code factoryTransformer} if you want that.
56 *
57 * @param factory the factory to call, not null
58 */
59 public FactoryTransformer(final Factory<? extends R> factory) {
60 iFactory = factory;
61 }
62
63 /**
64 * Gets the factory.
65 *
66 * @return the factory
67 * @since 3.1
68 */
69 public Factory<? extends R> getFactory() {
70 return iFactory;
71 }
72
73 /**
74 * Transforms the input by ignoring the input and returning the result of
75 * calling the decorated factory.
76 *
77 * @param input the input object to transform
78 * @return the transformed result
79 */
80 @Override
81 public R transform(final T input) {
82 return iFactory.get();
83 }
84
85 }