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The Apache Commons Collections package contains types that extend and augment the Java Collections Framework.
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4.functors;
import java.io.Serializable;
import org.apache.commons.collections4.FunctorException;
import org.apache.commons.collections4.Transformer;
/**
* Transformer implementation that always throws an exception.
*
* @since 3.0
*/
public final class ExceptionTransformer implements Transformer, Serializable {
/** Serial version UID */
private static final long serialVersionUID = 7179106032121985545L;
/** Singleton predicate instance */
@SuppressWarnings("rawtypes") // the static instance works for all types
public static final Transformer INSTANCE = new ExceptionTransformer<>();
/**
* Factory returning the singleton instance.
*
* @param the input type
* @param the output type
* @return the singleton instance
* @since 3.1
*/
@SuppressWarnings("unchecked") // the static instance works for all types
public static Transformer exceptionTransformer() {
return INSTANCE;
}
/**
* Restricted constructor.
*/
private ExceptionTransformer() {
super();
}
/**
* Transforms the input to result by cloning it.
*
* @param input the input object to transform
* @return never
* @throws FunctorException always
*/
@Override
public O transform(final I input) {
throw new FunctorException("ExceptionTransformer invoked");
}
private Object readResolve() {
return INSTANCE;
}
}