    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.FunctorException;
    022import org.apache.commons.collections4.Predicate;
    023
    024/**
    025 * Predicate implementation that always throws an exception.
    026 *
    027 * @param <T> the type of the input to the predicate.
    028 * @since 3.0
    029 */
    030public final class ExceptionPredicate<T> extends AbstractPredicate<T> implements 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 Predicate INSTANCE = new ExceptionPredicate<>();
    038
    039    /**
    040     * Factory returning the singleton instance.
    041     *
    042     * @param <T>  the object type
    043     * @return the singleton instance
    044     * @since 3.1
    045     */
    046    public static <T> Predicate<T> exceptionPredicate() {
    047        return INSTANCE;
    048    }
    049
    050    /**
    051     * Restricted constructor.
    052     */
    053    private ExceptionPredicate() {
    054    }
    055
    056    /**
    057     * Returns the singleton instance.
    058     *
    059     * @return the singleton instance.
    060     */
    061    private Object readResolve() {
    062        return INSTANCE;
    063    }
    064
    065    /**
    066     * Evaluates the predicate always throwing an exception.
    067     *
    068     * @param object  the input object
    069     * @return never
    070     * @throws FunctorException always
    071     */
    072    @Override
    073    public boolean test(final T object) {
    074        throw new FunctorException("ExceptionPredicate invoked");
    075    }
    076
    077}