    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.lang3.function;
    019
    020import java.util.function.ToDoubleBiFunction;
    021
    022/**
    023 * A functional interface like {@link ToDoubleBiFunction} that declares a {@code Throwable}.
    024 *
    025 * @param <T> the type of the first argument to the function
    026 * @param <U> the type of the second argument to the function
    027 * @param <E> Thrown exception.
    028 * @since 3.11
    029 */
    030@FunctionalInterface
    031public interface FailableToDoubleBiFunction<T, U, E extends Throwable> {
    032
    033    /** NOP singleton */
    034    @SuppressWarnings("rawtypes")
    035    FailableToDoubleBiFunction NOP = (t, u) -> 0d;
    036
    037    /**
    038     * Returns The NOP singleton.
    039     *
    040     * @param <T> the type of the first argument to the function
    041     * @param <U> the type of the second argument to the function
    042     * @param <E> Thrown exception.
    043     * @return The NOP singleton.
    044     */
    045    static <T, U, E extends Throwable> FailableToDoubleBiFunction<T, U, E> nop() {
    046        return NOP;
    047    }
    048
    049    /**
    050     * Applies this function to the given arguments.
    051     *
    052     * @param t the first function argument
    053     * @param u the second function argument
    054     * @return the function result
    055     * @throws E Thrown when the function fails.
    056     */
    057    double applyAsDouble(T t, U u) throws E;
    058}