001/*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.util.concurrent;
018
019import com.google.common.annotations.GwtCompatible;
020
021import java.util.concurrent.Future;
022
023import javax.annotation.Nullable;
024
025/**
026 * Transforms a value, possibly asynchronously. For an example usage and more
027 * information, see
028 * {@link Futures#transformAsync(ListenableFuture, AsyncFunction)}.
029 *
030 * @author Chris Povirk
031 * @since 11.0
032 */
033@GwtCompatible
034public interface AsyncFunction<I, O> {
035  /**
036   * Returns an output {@code Future} to use in place of the given {@code
037   * input}. The output {@code Future} need not be {@linkplain Future#isDone
038   * done}, making {@code AsyncFunction} suitable for asynchronous derivations.
039   *
040   * <p>Throwing an exception from this method is equivalent to returning a
041   * failing {@code Future}.
042   */
043  ListenableFuture<O> apply(@Nullable I input) throws Exception;
044}