| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.util.concurrent; |
| |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.TimeoutException; |
| |
| /** |
| * This interface defines an asynchronous {@link #get(long, TimeUnit)} method. |
| * |
| * When the return value is still being computed, invoking |
| * {@link #get(long, TimeUnit)} will result in a {@link TimeoutException}. |
| * The method should be invoked again and again |
| * until the underlying computation is completed. |
| * |
| * @param <R> The type of the return value. |
| * @param <E> The exception type that the underlying implementation may throw. |
| */ |
| public interface AsyncGet<R, E extends Throwable> { |
| /** |
| * Get the result. |
| * |
| * @param timeout The maximum time period to wait. |
| * When timeout == 0, it does not wait at all. |
| * When timeout < 0, it waits indefinitely. |
| * @param unit The unit of the timeout value |
| * @return the result, which is possibly null. |
| * @throws E an exception thrown by the underlying implementation. |
| * @throws TimeoutException if it cannot return after the given time period. |
| * @throws InterruptedException if the thread is interrupted. |
| */ |
| R get(long timeout, TimeUnit unit) |
| throws E, TimeoutException, InterruptedException; |
| |
| /** @return true if the underlying computation is done; false, otherwise. */ |
| boolean isDone(); |
| |
| /** Utility */ |
| class Util { |
| /** Use {@link #get(long, TimeUnit)} timeout parameters to wait. */ |
| public static void wait(Object obj, long timeout, TimeUnit unit) |
| throws InterruptedException { |
| if (timeout < 0) { |
| obj.wait(); |
| } else if (timeout > 0) { |
| obj.wait(unit.toMillis(timeout)); |
| } |
| } |
| } |
| } |