    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.Factory;
    022import org.apache.commons.collections4.FunctorException;
    023
    024/**
    025 * Factory implementation that always throws an exception.
    026 *
    027 * @since 3.0
    028 */
    029public final class ExceptionFactory<T> implements Factory<T>, Serializable {
    030
    031    /** Serial version UID */
    032    private static final long serialVersionUID = 7179106032121985545L;
    033
    034    /** Singleton predicate instance */
    035    @SuppressWarnings("rawtypes") // the static instance works for all types
    036    public static final Factory INSTANCE = new ExceptionFactory<>();
    037
    038    /**
    039     * Factory returning the singleton instance.
    040     *
    041     * @param <T>  the type the factory creates
    042     * @return the singleton instance
    043     * @since 3.1
    044     */
    045    @SuppressWarnings("unchecked") // the static instance works for all types
    046    public static <T> Factory<T> exceptionFactory() {
    047        return INSTANCE;
    048    }
    049
    050    /**
    051     * Restricted constructor.
    052     */
    053    private ExceptionFactory() {
    054        super();
    055    }
    056
    057    /**
    058     * Always throws an exception.
    059     *
    060     * @return never
    061     * @throws FunctorException always
    062     */
    063    @Override
    064    public T create() {
    065        throw new FunctorException("ExceptionFactory invoked");
    066    }
    067
    068    private Object readResolve() {
    069        return INSTANCE;
    070    }
    071
    072}