flink-core-api/src/main/java/org/apache/flink/util/function/BiFunctionWithException.java

/*
 * 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.flink.util.function;

import java.util.function.BiFunction;

/**
 * {@link BiFunction} interface which can throw exceptions.
 *
 * @param <T> type of the first parameter
 * @param <U> type of the second parameter
 * @param <R> type of the return type
 * @param <E> type of the exception which can be thrown
 */
@FunctionalInterface
public interface BiFunctionWithException<T, U, R, E extends Throwable> {

    /**
     * Apply the given values t and u to obtain the resulting value. The operation can throw an
     * exception.
     *
     * @param t first parameter
     * @param u second parameter
     * @return result value
     * @throws E if the operation fails
     */
    R apply(T t, U u) throws E;

    /**
     * Convert at {@link BiFunctionWithException} into a {@link BiFunction}.
     *
     * @param biFunctionWithException function with exception to convert into a function
     * @param <A> input type
     * @param <B> output type
     * @return {@link BiFunction} which throws all checked exception as an unchecked exception.
     */
    static <A, B, C> BiFunction<A, B, C> unchecked(
            BiFunctionWithException<A, B, C, ?> biFunctionWithException) {
        return (A a, B b) -> {
            try {
                return biFunctionWithException.apply(a, b);
            } catch (Throwable t) {
                ThrowingExceptionUtils.rethrow(t);
                // we need this to appease the compiler :-(
                return null;
            }
        };
    }
}