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 */
017package org.apache.commons.collections4.functors;
018
019import java.io.Serializable;
020
021import org.apache.commons.collections4.Closure;
022import org.apache.commons.collections4.FunctorException;
023
024/**
025 * Closure implementation that always throws an exception.
026 *
027 * @since 3.0
028 * @version $Id: ExceptionClosure.html 887892 2013-11-24 13:43:45Z tn $
029 */
030public final class ExceptionClosure<E> implements Closure<E>, Serializable {
031
032    /** Serial version UID */
033    private static final long serialVersionUID = 7179106032121985545L;
034
035    /** Singleton predicate instance */
036    @SuppressWarnings("rawtypes") // the static instance works for all types
037    public static final Closure INSTANCE = new ExceptionClosure<Object>();
038
039    /**
040     * Factory returning the singleton instance.
041     *
042     * @param <E> the type that the closure acts on
043     * @return the singleton instance
044     * @since 3.1
045     */
046    @SuppressWarnings("unchecked")  // the static instance works for all types
047    public static <E> Closure<E> exceptionClosure() {
048        return (Closure<E>) INSTANCE;
049    }
050
051    /**
052     * Restricted constructor.
053     */
054    private ExceptionClosure() {
055        super();
056    }
057
058    /**
059     * Always throw an exception.
060     *
061     * @param input  the input object
062     * @throws FunctorException always
063     */
064    public void execute(final E input) {
065        throw new FunctorException("ExceptionClosure invoked");
066    }
067
068    private Object readResolve() {
069        return INSTANCE;
070    }
071
072}