001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.functors; 018 019 import java.io.Serializable; 020 021 import org.apache.commons.collections.FunctorException; 022 import org.apache.commons.collections.Transformer; 023 024 /** 025 * Transformer implementation that always throws an exception. 026 * 027 * @since Commons Collections 3.0 028 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 029 * 030 * @author Stephen Colebourne 031 */ 032 public final class ExceptionTransformer implements Transformer, Serializable { 033 034 /** Serial version UID */ 035 private static final long serialVersionUID = 7179106032121985545L; 036 037 038 /** Singleton predicate instance */ 039 public static final Transformer INSTANCE = new ExceptionTransformer(); 040 041 /** 042 * Factory returning the singleton instance. 043 * 044 * @return the singleton instance 045 * @since Commons Collections 3.1 046 */ 047 public static Transformer getInstance() { 048 return INSTANCE; 049 } 050 051 /** 052 * Restricted constructor. 053 */ 054 private ExceptionTransformer() { 055 super(); 056 } 057 058 /** 059 * Transforms the input to result by cloning it. 060 * 061 * @param input the input object to transform 062 * @return never 063 * @throws FunctorException always 064 */ 065 public Object transform(Object input) { 066 throw new FunctorException("ExceptionTransformer invoked"); 067 } 068 069 }