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
21 import org.apache.commons.collections4.Transformer;
22
23 /**
24 * Transformer implementation that returns the result of calling
25 * {@code String.valueOf} on the input object.
26 *
27 * @since 3.0
28 */
29 public final class StringValueTransformer<T> implements Transformer<T, String>, Serializable {
30
31 /** Serial version UID */
32 private static final long serialVersionUID = 7511110693171758606L;
33
34 /** Singleton predicate instance */
35 private static final Transformer<Object, String> INSTANCE = new StringValueTransformer<>();
36
37 /**
38 * Factory returning the singleton instance.
39 *
40 * @param <T> the input type
41 * @return the singleton instance
42 * @since 3.1
43 */
44 @SuppressWarnings("unchecked")
45 public static <T> Transformer<T, String> stringValueTransformer() {
46 return (Transformer<T, String>) INSTANCE;
47 }
48
49 /**
50 * Restricted constructor.
51 */
52 private StringValueTransformer() {
53 }
54
55 private Object readResolve() {
56 return INSTANCE;
57 }
58
59 /**
60 * Transforms the input to result by calling {@code String.valueOf}.
61 *
62 * @param input the input object to transform
63 * @return the transformed result
64 */
65 @Override
66 public String transform(final T input) {
67 return String.valueOf(input);
68 }
69
70 }