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     */
017    package org.apache.commons.collections.functors;
018    
019    import java.io.Serializable;
020    
021    import org.apache.commons.collections.FunctorException;
022    import org.apache.commons.collections.Predicate;
023    
024    /**
025     * Predicate implementation that always throws an exception.
026     * 
027     * @since Commons Collections 3.0
028     * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
029     *
030     * @author Stephen Colebourne
031     */
032    public final class ExceptionPredicate implements Predicate, Serializable {
033    
034        /** Serial version UID */
035        private static final long serialVersionUID = 7179106032121985545L;
036        
037        /** Singleton predicate instance */
038        public static final Predicate INSTANCE = new ExceptionPredicate();
039    
040        /**
041         * Factory returning the singleton instance.
042         * 
043         * @return the singleton instance
044         * @since Commons Collections 3.1
045         */
046        public static Predicate getInstance() {
047            return INSTANCE;
048        }
049    
050        /**
051         * Restricted constructor.
052         */
053        private ExceptionPredicate() {
054            super();
055        }
056    
057        /**
058         * Evaluates the predicate always throwing an exception.
059         * 
060         * @param object  the input object
061         * @return never
062         * @throws FunctorException always
063         */
064        public boolean evaluate(Object object) {
065            throw new FunctorException("ExceptionPredicate invoked");
066        }
067        
068    }