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.functors; 18 19 import java.io.Serializable; 20 21 import org.apache.commons.collections4.FunctorException; 22 import org.apache.commons.collections4.Transformer; 23 24 /** 25 * Transformer implementation that always throws an exception. 26 * 27 * @since 3.0 28 */ 29 public final class ExceptionTransformer<I, O> implements Transformer<I, O>, Serializable { 30 31 /** Serial version UID */ 32 private static final long serialVersionUID = 7179106032121985545L; 33 34 /** Singleton predicate instance */ 35 @SuppressWarnings("rawtypes") // the static instance works for all types 36 public static final Transformer INSTANCE = new ExceptionTransformer<>(); 37 38 /** 39 * Factory returning the singleton instance. 40 * 41 * @param <I> the input type 42 * @param <O> the output type 43 * @return the singleton instance 44 * @since 3.1 45 */ 46 public static <I, O> Transformer<I, O> exceptionTransformer() { 47 return INSTANCE; 48 } 49 50 /** 51 * Restricted constructor. 52 */ 53 private ExceptionTransformer() { 54 } 55 56 private Object readResolve() { 57 return INSTANCE; 58 } 59 60 /** 61 * Transforms the input to result by cloning it. 62 * 63 * @param input the input object to transform 64 * @return never 65 * @throws FunctorException always 66 */ 67 @Override 68 public O transform(final I input) { 69 throw new FunctorException("ExceptionTransformer invoked"); 70 } 71 72 }