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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  
19  import java.io.Serializable;
20  
21  import org.apache.commons.collections4.FunctorException;
22  import org.apache.commons.collections4.Predicate;
23  
24  /**
25   * Predicate implementation that always throws an exception.
26   *
27   * @since 3.0
28   */
29  public final class ExceptionPredicate<T> implements Predicate<T>, Serializable {
30  
31      /** Serial version UID */
32      private static final long serialVersionUID = 7179106032121985545L;
33  
34      /** Singleton predicate instance */
35      @SuppressWarnings("rawtypes") // the static instance works for all types
36      public static final Predicate INSTANCE = new ExceptionPredicate<>();
37  
38      /**
39       * Factory returning the singleton instance.
40       *
41       * @param <T>  the object type
42       * @return the singleton instance
43       * @since 3.1
44       */
45      public static <T> Predicate<T> exceptionPredicate() {
46          return INSTANCE;
47      }
48  
49      /**
50       * Restricted constructor.
51       */
52      private ExceptionPredicate() {
53          super();
54      }
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 evaluate(final T object) {
65          throw new FunctorException("ExceptionPredicate invoked");
66      }
67  
68      private Object readResolve() {
69          return INSTANCE;
70      }
71  
72  }