Helfer Queue

Jan Burse, erstellt 15. Sep 2018
package example08;
import java.util.ArrayList;
/**
* <p>Java code for the queue example.</p>
* <p>The Java queue.</p>
* <p/>
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
* <p/>
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies GmbH. If the company was not the originator of some
* excerpts, XLOG Technologies GmbH has at least obtained the right to
* reproduce, change and translate the information.
* <p/>
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
* <p/>
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
* <p/>
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
*/
public final class Queue {
private final ArrayList<QueueEntry> planned = new ArrayList<QueueEntry>();
/**
* <p>Create a new queue.</p>
*/
public Queue() {
}
/**
* <p>Take the next runnable from the queue.</p>
*
* @return The runnable.
* @throws InterruptedException Thread was interrupted.
*/
public Runnable take() throws InterruptedException {
synchronized (this) {
for (; ; ) {
if (planned.size() == 0) {
this.wait();
} else {
QueueEntry entry = planned.get(0);
long sleep = entry.getWhen() - System.currentTimeMillis();
if (sleep <= 0) {
planned.remove(0);
return entry.getRunnable();
} else {
this.wait(sleep);
}
}
}
}
}
/**
* <p>Post a runnable on the queue.</p>
*
* @param r The runnable.
* @param w The time point.
*/
public void post(Runnable r, long w) {
QueueEntry entry = new QueueEntry(r, w);
synchronized (this) {
int i = 0;
for (; i < planned.size(); i++) {
QueueEntry entry2 = planned.get(i);
if (w < entry2.getWhen())
break;
}
planned.add(i, entry);
this.notifyAll();
}
}
}

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