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;
18
19 import java.util.function.Function;
20
21 /**
22 * Defines a functor interface implemented by classes that transform one
23 * object into another.
24 * <p>
25 * A {@code Transformer} converts the input object to the output object.
26 * The input object should be left unchanged.
27 * Transformers are typically used for type conversions, or extracting data
28 * from an object.
29 * </p>
30 * <p>
31 * Standard implementations of common transformers are provided by
32 * {@link TransformerUtils}. These include method invocation, returning a constant,
33 * cloning and returning the string value.
34 * </p>
35 *
36 * @param <T> the input type to the transformer
37 * @param <R> the output type from the transformer
38 *
39 * @since 1.0
40 * @deprecated Use {@link Function}.
41 */
42 @Deprecated
43 public interface Transformer<T, R> extends Function<T, R> {
44
45 @Override
46 default R apply(final T t) {
47 return transform(t);
48 }
49
50 /**
51 * Transforms the input object (leaving it unchanged) into some output object.
52 *
53 * @param input the object to be transformed, should be left unchanged
54 * @return a transformed object
55 * @throws ClassCastException (runtime) if the input is the wrong class
56 * @throws IllegalArgumentException (runtime) if the input is invalid
57 * @throws FunctorException (runtime) if the transform cannot be completed
58 */
59 R transform(T input);
60
61 }