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.Factory;
22 import org.apache.commons.collections4.FunctorException;
23
24 /**
25 * Factory implementation that always throws an exception.
26 *
27 * @since 3.0
28 */
29 public final class ExceptionFactory<T> implements Factory<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 Factory INSTANCE = new ExceptionFactory<>();
37
38 /**
39 * Factory returning the singleton instance.
40 *
41 * @param <T> the type the factory creates
42 * @return the singleton instance
43 * @since 3.1
44 */
45 public static <T> Factory<T> exceptionFactory() {
46 return INSTANCE;
47 }
48
49 /**
50 * Restricted constructor.
51 */
52 private ExceptionFactory() {
53 }
54
55 /**
56 * Always throws an exception.
57 *
58 * @return never
59 * @throws FunctorException always
60 */
61 @Override
62 public T create() {
63 throw new FunctorException("ExceptionFactory invoked");
64 }
65
66 private Object readResolve() {
67 return INSTANCE;
68 }
69
70 }