org.apache.hadoop.util.concurrent.AsyncGet Maven / Gradle / Ivy
/**
* 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 The type of the return value.
* @param The exception type that the underlying implementation may throw.
*/
public interface AsyncGet {
/**
* 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));
}
}
}
}