106 lines
3.2 KiB
Java
106 lines
3.2 KiB
Java
// concurrency/DelayQueueDemo.java
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// ©2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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import java.util.concurrent.*;
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import java.util.*;
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import static java.util.concurrent.TimeUnit.*;
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class DelayedTask implements Runnable, Delayed {
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private static int counter = 0;
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private final int id = counter++;
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private final int delta;
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private final long trigger;
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protected static List<DelayedTask> sequence =
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new ArrayList<>();
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public DelayedTask(int delayInMilliseconds) {
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delta = delayInMilliseconds;
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trigger = System.nanoTime() +
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NANOSECONDS.convert(delta, MILLISECONDS);
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sequence.add(this);
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}
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@Override
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public long getDelay(TimeUnit unit) {
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return unit.convert(
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trigger - System.nanoTime(), NANOSECONDS);
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}
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@Override
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public int compareTo(Delayed arg) {
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DelayedTask that = (DelayedTask)arg;
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if(trigger < that.trigger) return -1;
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if(trigger > that.trigger) return 1;
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return 0;
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}
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@Override
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public void run() { System.out.print(this + " "); }
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@Override
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public String toString() {
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return String.format("[%1$-4d]", delta) +
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" Task " + id;
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}
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public String summary() {
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return "(" + id + ":" + delta + ")";
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}
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public static class EndSentinel extends DelayedTask {
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private ExecutorService exec;
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public EndSentinel(int delay, ExecutorService e) {
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super(delay);
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exec = e;
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}
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@Override
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public void run() {
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for(DelayedTask pt : sequence) {
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System.out.print(pt.summary() + " ");
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}
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System.out.println();
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System.out.println(this + " Calling shutdownNow()");
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exec.shutdownNow();
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}
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}
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}
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class DelayedTaskConsumer implements Runnable {
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private DelayQueue<DelayedTask> q;
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public DelayedTaskConsumer(DelayQueue<DelayedTask> q) {
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this.q = q;
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}
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@Override
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public void run() {
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try {
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while(!Thread.interrupted())
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q.take().run(); // Run task with the current thread
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} catch(InterruptedException e) {
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// Acceptable way to exit
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}
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System.out.println("Finished DelayedTaskConsumer");
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}
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}
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public class DelayQueueDemo {
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public static void main(String[] args) {
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Random rand = new Random(47);
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ExecutorService exec = Executors.newCachedThreadPool();
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DelayQueue<DelayedTask> queue =
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new DelayQueue<>();
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// Fill with tasks that have random delays:
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for(int i = 0; i < 20; i++)
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queue.put(new DelayedTask(rand.nextInt(5000)));
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// Set the stopping point
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queue.add(new DelayedTask.EndSentinel(5000, exec));
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exec.execute(new DelayedTaskConsumer(queue));
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}
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}
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/* Output:
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[128 ] Task 11 [200 ] Task 7 [429 ] Task 5 [520 ] Task 18
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[555 ] Task 1 [961 ] Task 4 [998 ] Task 16 [1207] Task 9
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[1693] Task 2 [1809] Task 14 [1861] Task 3 [2278] Task 15
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[3288] Task 10 [3551] Task 12 [4258] Task 0 [4258] Task 19
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[4522] Task 8 [4589] Task 13 [4861] Task 17 [4868] Task 6
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(0:4258) (1:555) (2:1693) (3:1861) (4:961) (5:429) (6:4868)
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(7:200) (8:4522) (9:1207) (10:3288) (11:128) (12:3551)
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(13:4589) (14:1809) (15:2278) (16:998) (17:4861) (18:520)
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(19:4258) (20:5000)
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[5000] Task 20 Calling shutdownNow()
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Finished DelayedTaskConsumer
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*/
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