ExceptionPredicate.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *      http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.apache.commons.collections4.functors;

  18. import java.io.Serializable;

  19. import org.apache.commons.collections4.FunctorException;
  20. import org.apache.commons.collections4.Predicate;

  21. /**
  22.  * Predicate implementation that always throws an exception.
  23.  *
  24.  * @param <T> the type of the input to the predicate.
  25.  * @since 3.0
  26.  */
  27. public final class ExceptionPredicate<T> extends AbstractPredicate<T> implements Serializable {

  28.     /** Serial version UID */
  29.     private static final long serialVersionUID = 7179106032121985545L;

  30.     /** Singleton predicate instance */
  31.     @SuppressWarnings("rawtypes") // the static instance works for all types
  32.     public static final Predicate INSTANCE = new ExceptionPredicate<>();

  33.     /**
  34.      * Factory returning the singleton instance.
  35.      *
  36.      * @param <T>  the object type
  37.      * @return the singleton instance
  38.      * @since 3.1
  39.      */
  40.     public static <T> Predicate<T> exceptionPredicate() {
  41.         return INSTANCE;
  42.     }

  43.     /**
  44.      * Restricted constructor.
  45.      */
  46.     private ExceptionPredicate() {
  47.     }

  48.     /**
  49.      * Returns the singleton instance.
  50.      *
  51.      * @return the singleton instance.
  52.      */
  53.     private Object readResolve() {
  54.         return INSTANCE;
  55.     }

  56.     /**
  57.      * Evaluates the predicate always throwing an exception.
  58.      *
  59.      * @param object  the input object
  60.      * @return never
  61.      * @throws FunctorException always
  62.      */
  63.     @Override
  64.     public boolean test(final T object) {
  65.         throw new FunctorException("ExceptionPredicate invoked");
  66.     }

  67. }