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    
017    package com.google.common.util.concurrent;
018    
019    import com.google.common.annotations.Beta;
020    
021    import java.util.concurrent.Future;
022    
023    /**
024     * Transforms a value, possibly asynchronously. For an example usage and more
025     * information, see {@link Futures#transform(ListenableFuture, AsyncFunction)}.
026     *
027     * @author Chris Povirk
028     * @since 11.0
029     */
030    @Beta
031    public interface AsyncFunction<I, O> {
032      /**
033       * Returns an output {@code Future} to use in place of the given {@code
034       * input}. The output {@code Future} need not be {@linkplain Future#isDone
035       * done}, making {@code AsyncFunction} suitable for asynchronous derivations.
036       *
037       * <p>Throwing an exception from this method is equivalent to returning a
038       * failing {@code Future}.
039       */
040      ListenableFuture<O> apply(I input) throws Exception;
041    }