| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.commons.lang3.function; |
| |
| import java.util.Objects; |
| import java.util.function.Function; |
| |
| /** |
| * A functional interface like {@link Function} that declares a {@code Throwable}. |
| * |
| * @param <T> Input type 1. |
| * @param <R> Return type. |
| * @param <E> Thrown exception. |
| * @since 3.11 |
| */ |
| @FunctionalInterface |
| public interface FailableFunction<T, R, E extends Throwable> { |
| |
| /** NOP singleton */ |
| @SuppressWarnings("rawtypes") |
| FailableFunction NOP = t -> null; |
| |
| /** |
| * Returns a function that always returns its input argument. |
| * |
| * @param <T> the type of the input and output objects to the function |
| * @param <E> Thrown exception. |
| * @return a function that always returns its input argument |
| */ |
| static <T, E extends Throwable> FailableFunction<T, T, E> identity() { |
| return t -> t; |
| } |
| |
| /** |
| * Returns The NOP singleton. |
| * |
| * @param <T> Consumed type 1. |
| * @param <R> Return type. |
| * @param <E> Thrown exception. |
| * @return The NOP singleton. |
| */ |
| static <T, R, E extends Throwable> FailableFunction<T, R, E> nop() { |
| return NOP; |
| } |
| |
| /** |
| * Returns a composed {@code FailableFunction} like {@link Function#andThen(Function)}. |
| * |
| * @param <V> the output type of the {@code after} function, and of the composed function. |
| * @return a composed {@code FailableFunction} like {@link Function#andThen(Function)}. |
| * @param after the operation to perform after this one. |
| * @throws NullPointerException when {@code after} is null. |
| */ |
| default <V> FailableFunction<T, V, E> andThen(final FailableFunction<? super R, ? extends V, E> after) { |
| Objects.requireNonNull(after); |
| return (final T t) -> after.apply(apply(t)); |
| } |
| |
| /** |
| * Applies this function. |
| * |
| * @param input the input for the function |
| * @return the result of the function |
| * @throws E Thrown when the function fails. |
| */ |
| R apply(T input) throws E; |
| |
| /** |
| * Returns a composed {@code FailableFunction} like {@link Function#compose(Function)}. |
| * |
| * @param <V> the input type to the {@code before} function, and to the composed function. |
| * @param before the operator to apply before this one. |
| * @return a a composed {@code FailableFunction} like {@link Function#compose(Function)}. |
| * @throws NullPointerException if before is null. |
| * @see #andThen(FailableFunction) |
| */ |
| default <V> FailableFunction<V, R, E> compose(final FailableFunction<? super V, ? extends T, E> before) { |
| Objects.requireNonNull(before); |
| return (final V v) -> apply(before.apply(v)); |
| } |
| } |