001    /*
002     * Copyright (C) 2008 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.CancellationException;
022    import java.util.concurrent.ExecutionException;
023    import java.util.concurrent.Future;
024    import java.util.concurrent.TimeUnit;
025    import java.util.concurrent.TimeoutException;
026    
027    /**
028     * A {@code CheckedFuture} is a {@link ListenableFuture} that includes versions
029     * of the {@code get} methods that can throw a checked exception.  This makes it
030     * easier to create a future that executes logic which can throw an exception.
031     *
032     * <p>Common implementations include
033     * {@link Futures#immediateCheckedFuture}.
034     *
035     * <p>Implementations of this interface must adapt the exceptions thrown by
036     * {@code Future#get()}: {@link CancellationException},
037     * {@link ExecutionException} and {@link InterruptedException} into the type
038     * specified by the {@code E} type parameter.
039     *
040     * <p>This interface also extends the ListenableFuture interface to allow
041     * listeners to be added. This allows the future to be used as a normal
042     * {@link Future} or as an asynchronous callback mechanism as needed. This
043     * allows multiple callbacks to be registered for a particular task, and the
044     * future will guarantee execution of all listeners when the task completes.
045     *
046     * @author Sven Mawson
047     * @since 1.0
048     */
049    @Beta
050    public interface CheckedFuture<V, X extends Exception>
051        extends ListenableFuture<V> {
052    
053      /**
054       * Exception checking version of {@link Future#get()} that will translate
055       * {@link InterruptedException}, {@link CancellationException} and
056       * {@link ExecutionException} into application-specific exceptions.
057       *
058       * @return the result of executing the future.
059       * @throws X on interruption, cancellation or execution exceptions.
060       */
061      V checkedGet() throws X;
062    
063      /**
064       * Exception checking version of {@link Future#get(long, TimeUnit)} that will
065       * translate {@link InterruptedException}, {@link CancellationException} and
066       * {@link ExecutionException} into application-specific exceptions.  On
067       * timeout this method throws a normal {@link TimeoutException}.
068       *
069       * @return the result of executing the future.
070       * @throws TimeoutException if retrieving the result timed out.
071       * @throws X on interruption, cancellation or execution exceptions.
072       */
073      V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X;
074    }