001/*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.util.concurrent;
016
017import com.google.common.annotations.GwtCompatible;
018import java.util.concurrent.Future;
019import org.checkerframework.checker.nullness.qual.Nullable;
020
021/**
022 * Transforms a value, possibly asynchronously. For an example usage and more information, see
023 * {@link Futures#transformAsync(ListenableFuture, AsyncFunction, Executor)}.
024 *
025 * @author Chris Povirk
026 * @since 11.0
027 */
028@GwtCompatible
029@FunctionalInterface
030@ElementTypesAreNonnullByDefault
031public interface AsyncFunction<I extends @Nullable Object, O extends @Nullable Object> {
032  /**
033   * Returns an output {@code Future} to use in place of the given {@code input}. The output {@code
034   * Future} need not be {@linkplain Future#isDone done}, making {@code AsyncFunction} suitable for
035   * asynchronous derivations.
036   *
037   * <p>Throwing an exception from this method is equivalent to returning a failing {@code Future}.
038   */
039  ListenableFuture<O> apply(@ParametricNullness I input) throws Exception;
040}