001/*
002 * Copyright (C) 2015 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.Beta;
018import com.google.common.annotations.GwtCompatible;
019import java.util.concurrent.Future;
020import org.checkerframework.checker.nullness.qual.Nullable;
021
022/**
023 * Computes a value, possibly asynchronously. For an example usage and more information, see {@link
024 * Futures.FutureCombiner#callAsync(AsyncCallable, java.util.concurrent.Executor)}.
025 *
026 * <p>Much like {@link java.util.concurrent.Callable}, but returning a {@link ListenableFuture}
027 * result.
028 *
029 * @since 20.0
030 */
031@Beta
032@FunctionalInterface
033@GwtCompatible
034@ElementTypesAreNonnullByDefault
035public interface AsyncCallable<V extends @Nullable Object> {
036  /**
037   * Computes a result {@code Future}. The output {@code Future} need not be {@linkplain
038   * Future#isDone done}, making {@code AsyncCallable} suitable for asynchronous derivations.
039   *
040   * <p>Throwing an exception from this method is equivalent to returning a failing {@link
041   * ListenableFuture}.
042   */
043  ListenableFuture<V> call() throws Exception;
044}