1 /* 2 * Copyright (C) 2008 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.util.concurrent; 18 19 import com.google.common.annotations.Beta; 20 21 import java.util.concurrent.CancellationException; 22 import java.util.concurrent.ExecutionException; 23 import java.util.concurrent.Future; 24 import java.util.concurrent.TimeUnit; 25 import java.util.concurrent.TimeoutException; 26 27 /** 28 * A {@code CheckedFuture} is a {@link ListenableFuture} that includes versions 29 * of the {@code get} methods that can throw a checked exception. This makes it 30 * easier to create a future that executes logic which can throw an exception. 31 * 32 * <p>A common implementation is {@link Futures#immediateCheckedFuture}. 33 * 34 * <p>Implementations of this interface must adapt the exceptions thrown by 35 * {@code Future#get()}: {@link CancellationException}, 36 * {@link ExecutionException} and {@link InterruptedException} into the type 37 * specified by the {@code E} type parameter. 38 * 39 * <p>This interface also extends the ListenableFuture interface to allow 40 * listeners to be added. This allows the future to be used as a normal 41 * {@link Future} or as an asynchronous callback mechanism as needed. This 42 * allows multiple callbacks to be registered for a particular task, and the 43 * future will guarantee execution of all listeners when the task completes. 44 * 45 * <p>For a simpler alternative to CheckedFuture, consider accessing Future 46 * values with {@link Futures#get(Future, Class) Futures.get()}. 47 * 48 * @author Sven Mawson 49 * @since 1.0 50 */ 51 @Beta 52 public interface CheckedFuture<V, X extends Exception> 53 extends ListenableFuture<V> { 54 55 /** 56 * Exception checking version of {@link Future#get()} that will translate 57 * {@link InterruptedException}, {@link CancellationException} and 58 * {@link ExecutionException} into application-specific exceptions. 59 * 60 * @return the result of executing the future. 61 * @throws X on interruption, cancellation or execution exceptions. 62 */ 63 V checkedGet() throws X; 64 65 /** 66 * Exception checking version of {@link Future#get(long, TimeUnit)} that will 67 * translate {@link InterruptedException}, {@link CancellationException} and 68 * {@link ExecutionException} into application-specific exceptions. On 69 * timeout this method throws a normal {@link TimeoutException}. 70 * 71 * @return the result of executing the future. 72 * @throws TimeoutException if retrieving the result timed out. 73 * @throws X on interruption, cancellation or execution exceptions. 74 */ 75 V checkedGet(long timeout, TimeUnit unit) throws TimeoutException, X; 76 } 77
