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//: concurrency/DelayQueueDemo.java

import java.util.concurrent.*;

import java.util.*;

import static java.util.concurrent.TimeUnit.*;

import static net.mindview.util.Print.*;

class DelayedTask implements Runnable, Delayed {

private static int counter = 0;

private final int id = counter++;

private final int delta;

private final long trigger;

protected static List<DelayedTask> sequence =

new ArrayList<DelayedTask>();

public DelayedTask(int delayInMilliseconds) {

delta = delayInMilliseconds;

trigger = System.nanoTime() +

NANOSECONDS.convert(delta, MILLISECONDS);

sequence.add(this);

}

public long getDelay(TimeUnit unit) {

return unit.convert(

trigger - System.nanoTime(), NANOSECONDS);

}

public int compareTo(Delayed arg) {

DelayedTask that = (DelayedTask)arg;

if(trigger < that.trigger) return -1;

if(trigger > that.trigger) return 1;

return 0;

}

public void run() { printnb(this + " "); }

public String toString() {

return String.format("[%1$-4d]", delta) +

" Task " + id;

}

public String summary() {

return "(" + id + ":" + delta + ")";

}

public static class EndSentinel extends DelayedTask {

private ExecutorService exec;

public EndSentinel(int delay, ExecutorService e) {

super(delay);

exec = e;

}

public void run() {

for(DelayedTask pt : sequence) {

printnb(pt.summary() + " ");

}

print();

print(this + " Calling shutdownNow()");

exec.shutdownNow();

}

}

}

class DelayedTaskConsumer implements Runnable {

private DelayQueue<DelayedTask> q;

public DelayedTaskConsumer(DelayQueue<DelayedTask> q) {

this.q = q;

}

public void run() {

try {

while(!Thread.interrupted())

q.take().run(); // Run task with the current thread

} catch(InterruptedException e) {

// Acceptable way to exit

}

print("Finished DelayedTaskConsumer");

}

}

public class DelayQueueDemo {

public static void main(String[] args) {

Random rand = new Random(47);

ExecutorService exec = Executors.newCachedThreadPool();

DelayQueue<DelayedTask> queue =

new DelayQueue<DelayedTask>();

// Fill with tasks that have random delays:

for(int i = 0; i < 20; i++)

queue.put(new DelayedTask(rand.nextInt(5000)));

// Set the stopping point

queue.add(new DelayedTask.EndSentinel(5000, exec));

exec.execute(new DelayedTaskConsumer(queue));

}

} /* Output:

[128 ] Task 11 [200 ] Task 7 [429 ] Task 5 [520 ] Task 18 [555 ] Task 1 [961 ] Task 4 [998 ] Task 16 [1207] Task 9 [1693] Task 2 [1809] Task 14 [1861] Task 3 [2278] Task 15 [3288] Task 10 [3551] Task 12 [4258] Task 0 [4258] Task 19 [4522] Task 8 [4589] Task 13 [4861] Task 17 [4868] Task 6 (0:4258) (1:555) (2:1693) (3:1861) (4:961) (5:429) (6:4868) (7:200) (8:4522) (9:1207) (10:3288) (11:128) (12:3551) (13:4589) (14:1809) (15:2278) (16:998) (17:4861) (18:520) (19:4258) (20:5000)

[5000] Task 20 Calling shutdownNow()

Finished DelayedTaskConsumer

*///:~