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// lowlevel/DelayQueueDemo.java

// (c)2017 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

import java.util.*;

import java.util.stream.*;

import java.util.concurrent.*;

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

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(int delayInMilliseconds) {

delta = delayInMilliseconds;

trigger = System.nanoTime() +

NANOSECONDS.convert(delta, MILLISECONDS);

sequence.add(this);

}

@Override

public long getDelay(TimeUnit unit) {

return unit.convert(

trigger - System.nanoTime(), NANOSECONDS);

}

@Override

public int compareTo(Delayed arg) {

DelayedTask that = (DelayedTask)arg;

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

if(trigger > that.trigger) return 1;

return 0;

}

@Override

public void run() {

System.out.print(this + " ");

}

@Override

public String toString() {

return

String.format("[%d] Task %d", delta, id);

}

public String summary() {

return String.format("(%d:%d)", id, delta);

}

public static class EndTask extends DelayedTask {

EndTask(int delay) { super(delay); }

@Override

public void run() {

sequence.forEach(dt ->

System.out.println(dt.summary()));

}

}

}

public class DelayQueueDemo {

public static void

main(String[] args) throws Exception {

DelayQueue<DelayedTask> tasks =

Stream.concat( // Random delays:

new Random(47).ints(20, 0, 4000)

.mapToObj(DelayedTask::new),

// Add the summarizing task:

Stream.of(new DelayedTask.EndTask(4000)))

.collect(Collectors

.toCollection(DelayQueue::new));

while(tasks.size() > 0)

tasks.take().run();

}

}

/* Output:

[128] Task 12 [429] Task 6 [551] Task 13 [555] Task 2

[693] Task 3 [809] Task 15 [961] Task 5 [1258] Task 1

[1258] Task 20 [1520] Task 19 [1861] Task 4 [1998] Task

17 [2200] Task 8 [2207] Task 10 [2288] Task 11 [2522]

Task 9 [2589] Task 14 [2861] Task 18 [2868] Task 7

[3278] Task 16 (0:4000)

(1:1258)

(2:555)

(3:693)

(4:1861)

(5:961)

(6:429)

(7:2868)

(8:2200)

(9:2522)

(10:2207)

(11:2288)

(12:128)

(13:551)

(14:2589)

(15:809)

(16:3278)

(17:1998)

(18:2861)

(19:1520)

(20:1258)

*/