ExceptionTransformer


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.functors;
17  
18  import java.io.Serializable  ;
19  
20  import org.apache.commons.collections.FunctorException;
21  import org.apache.commons.collections.Transformer;
22  
23  /**
24   * Transformer implementation that always throws an exception.
25   * 
26   * @since Commons Collections 3.0
27   * @version $Revision: 1.7 $ $Date: 2004/05/16 11:36:31 $
28   *
29   * @author Stephen Colebourne
30   */
31  public final class ExceptionTransformer implements Transformer, Serializable   {
32  
33      /** Serial version UID */
34      static final long serialVersionUID = 7179106032121985545L;
35      
36  
37      /** Singleton predicate instance */
38      public static final Transformer INSTANCE = new ExceptionTransformer();
39  
40      /**
41       * Factory returning the singleton instance.
42       * 
43       * @return the singleton instance
44       * @since Commons Collections 3.1
45       */
46      public static Transformer getInstance() {
47          return INSTANCE;
48      }
49  
50      /**
51       * Restricted constructor.
52       */
53      private ExceptionTransformer() {
54          super();
55      }
56  
57      /**
58       * Transforms the input to result by cloning it.
59       * 
60       * @param input  the input object to transform
61       * @return never
62       * @throws FunctorException always
63       */
64      public Object   transform(Object   input) {
65          throw new FunctorException("ExceptionTransformer invoked");
66      }
67  
68  }
69
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