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.DoubleFunction;
21
22 /**
23 * A functional interface like {@link DoubleFunction} that declares a {@link Throwable}.
24 *
25 * @param <R> Return type.
26 * @param <E> The kind of thrown exception or error.
27 * @since 3.11
28 */
29 @FunctionalInterface
30 public interface FailableDoubleFunction<R, E extends Throwable> {
31
32 /** NOP singleton */
33 @SuppressWarnings("rawtypes")
34 FailableDoubleFunction NOP = t -> null;
35
36 /**
37 * Returns The NOP singleton.
38 *
39 * @param <R> Return type.
40 * @param <E> The kind of thrown exception or error.
41 * @return The NOP singleton.
42 */
43 @SuppressWarnings("unchecked")
44 static <R, E extends Throwable> FailableDoubleFunction<R, E> nop() {
45 return NOP;
46 }
47
48 /**
49 * Applies this function.
50 *
51 * @param input the input for the function
52 * @return the result of the function
53 * @throws E Thrown when the function fails.
54 */
55 R apply(double input) throws E;
56 }