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
18 package org.apache.commons.lang3.function;
19
20 import java.util.function.Supplier;
21
22 /**
23 * A functional interface like {@link Supplier} that declares a {@link Throwable}.
24 *
25 * @param <T> Return type.
26 * @param <E> The kind of thrown exception or error.
27 * @since 3.11
28 */
29 @FunctionalInterface
30 public interface FailableSupplier<T, E extends Throwable> {
31
32 /**
33 * Returns the singleton supplier that always returns null.
34 * <p>
35 * This supplier never throws an exception.
36 * </p>
37 *
38 * @since 3.14.0
39 */
40 @SuppressWarnings("rawtypes")
41 FailableSupplier NUL = () -> null;
42
43 /**
44 * Returns the singleton supplier that always returns null.
45 * <p>
46 * This supplier never throws an exception.
47 * </p>
48 *
49 * @param <T> Supplied type.
50 * @param <E> The kind of thrown exception or error.
51 * @return The NUL singleton.
52 * @since 3.14.0
53 */
54 @SuppressWarnings("unchecked")
55 static <T, E extends Exception> FailableSupplier<T, E> nul() {
56 return NUL;
57 }
58
59 /**
60 * Supplies an object
61 *
62 * @return a result
63 * @throws E if the supplier fails
64 */
65 T get() throws E;
66 }