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1   /*
2    *  Copyright 2001-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  package net.sf.collections15;
17  
18  /***
19   * Defines a functor interface implemented by classes that transform one object
20   * into another.
21   * <p/>
22   * A <code>Transformer</code> converts the input object to the output object.
23   * The input object should be left unchanged. Transformers are typically used
24   * for type conversions, or extracting data from an object.
25   * <p/>
26   * Standard implementations of common transformers are provided by {@link
27   * net.sf.collections15.functors.transformer.TransformerUtils}. These include
28   * method invokation, returning a constant, cloning and returning the string
29   * value.
30   *
31   * @author James Strachan
32   * @author Stephen Colebourne
33   * @version $Revision: 1.2 $ $Date: 2004/10/17 01:02:42 $
34   * @since Commons Collections15 1.0
35   */
36  public interface Transformer <I, O>
37  {
38  
39      /***
40       * Transforms the input object (leaving it unchanged) into some output
41       * object.
42       *
43       * @param input the object to be transformed, should be left unchanged
44       *
45       * @return a transformed object
46       *
47       * @throws ClassCastException       (runtime) if the input is the wrong
48       *                                  class
49       * @throws IllegalArgumentException (runtime) if the input is invalid
50       * @throws net.sf.collections15.functors.FunctorException
51       *                                  (runtime) if the transform cannot be
52       *                                  completed
53       */
54      public O transform(I input);
55  
56  }