Transformer


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 org.apache.commons.collections;
17  
18  /**
19   * Defines a functor interface implemented by classes that transform one
20   * object 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.
24   * Transformers are typically used for type conversions, or extracting data
25   * from an object.
26   * <p>
27   * Standard implementations of common transformers are provided by
28   * {@link TransformerUtils}. These include method invokation, returning a constant,
29   * cloning and returning the string value.
30   * 
31   * @since Commons Collections 1.0
32   * @version $Revision: 1.10 $ $Date: 2004/04/14 20:08:57 $
33   * 
34   * @author James Strachan
35   * @author Stephen Colebourne
36   */
37  public interface Transformer {
38  
39      /**
40       * Transforms the input object (leaving it unchanged) into some output object.
41       *
42       * @param input  the object to be transformed, should be left unchanged
43       * @return a transformed object
44       * @throws ClassCastException (runtime) if the input is the wrong class
45       * @throws IllegalArgumentException (runtime) if the input is invalid
46       * @throws FunctorException (runtime) if the transform cannot be completed
47       */
48      public Object   transform(Object   input);
49  
50  }
51
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