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 * @since 3.0
028 */
029public final class ExceptionPredicate<T> implements Predicate<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 Predicate INSTANCE = new ExceptionPredicate<>();
037
038    /**
039     * Factory returning the singleton instance.
040     *
041     * @param <T>  the object type
042     * @return the singleton instance
043     * @since 3.1
044     */
045    public static <T> Predicate<T> exceptionPredicate() {
046        return INSTANCE;
047    }
048
049    /**
050     * Restricted constructor.
051     */
052    private ExceptionPredicate() {
053    }
054
055    /**
056     * Evaluates the predicate always throwing an exception.
057     *
058     * @param object  the input object
059     * @return never
060     * @throws FunctorException always
061     */
062    @Override
063    public boolean evaluate(final T object) {
064        throw new FunctorException("ExceptionPredicate invoked");
065    }
066
067    private Object readResolve() {
068        return INSTANCE;
069    }
070
071}