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.Closure;
22 import org.apache.commons.collections4.FunctorException;
23
24 /**
25 * Closure implementation that always throws an exception.
26 *
27 * @param <T> the type of the input to the operation.
28 * @since 3.0
29 */
30 public final class ExceptionClosure<T> implements Closure<T>, Serializable {
31
32 /** Serial version UID */
33 private static final long serialVersionUID = 7179106032121985545L;
34
35 /** Singleton predicate instance */
36 @SuppressWarnings("rawtypes") // the static instance works for all types
37 public static final Closure INSTANCE = new ExceptionClosure<>();
38
39 /**
40 * Factory returning the singleton instance.
41 *
42 * @param <T> the type of the input to the operation.
43 * @return the singleton instance
44 * @since 3.1
45 */
46 public static <T> Closure<T> exceptionClosure() {
47 return INSTANCE;
48 }
49
50 /**
51 * Restricted constructor.
52 */
53 private ExceptionClosure() {
54 }
55
56 /**
57 * Always throw an exception.
58 *
59 * @param input the input object
60 * @throws FunctorException always
61 */
62 @Override
63 public void execute(final T input) {
64 throw new FunctorException("ExceptionClosure invoked");
65 }
66
67 /**
68 * Returns the singleton instance.
69 *
70 * @return the singleton instance.
71 */
72 private Object readResolve() {
73 return INSTANCE;
74 }
75
76 }