How to generate random numbers at set time intervals?

Question

I have developed code in Java for generating ten random numbers from a range 0 to 99. The problem is I need to generate a random number for every 2 min. I am new to this area and need your views.

Answer 1

This example adds a random number to a blocking dequeue every two minutes. You can take the numbers from the queue when you need them. You can use java.util.Timer as a lightweight facility to schedule the number generation or you can use java.util.concurrent.ScheduledExecutorService for a more versatile solution if you need more sophistication in the future. By writing the numbers to a dequeue, you have a unified interface of retrieving numbers from both facilities.

First, we set up the blocking queue:

final BlockingDequeue<Integer> queue = new LinkedBlockingDequeue<Integer>();

Here is the setup with java.utilTimer:

TimerTask task = new TimerTask() {
    public void run() {
        queue.put(Math.round(Math.random() * 99));
        // or use whatever method you chose to generate the number...
    }
};
Timer timer = new Timer(true)Timer();
timer.schedule(task, 0, 120000); 

This is the setup with java.util.concurrent.ScheduledExecutorService

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
Runnable task = new Runnable() {
    public void run() {
        queue.put(Math.round(Math.random() * 99));
        // or use whatever method you chose to generate the number...
    }
};
scheduler.scheduleAtFixedRate(task, 0, 120, SECONDS);

Now, you can get a new random number from the queue every two minutes. The queue will block until a new number becomes available...

int numbers = 100;
for (int i = 0; i < numbers; i++) {
    Inetger rand = queue.remove();
    System.out.println("new random number: " + rand);
}

Once you are done, you can terminate the scheduler. If you used the Timer, just do

timer.cancel();

If you used ScheduledExecutorService you can do

scheduler.shutdown();

Answer 2

You have two requirements which are unrelated:

1. Generate random numbers
2. Perform the task every 2 minutes.

To do anything every 2 minutes you can use a ScheduledExecutorService.

Answer 3

You can schedule your program to be run once every two minutes using whatever scheduling features are available to you in your target environment (eg, cron , at , Windows Scheduled Tasks, etc.).

Or you can use the Thread#sleep method to suspend your application for 2,000ms and run your code in a loop:

while (loopCondition) {
    /* ...generate random number... */

    // Suspend execution for 2 minutes
    Thread.currentThread().sleep(1000 * 60 * 2);
}

(That's just example code, you'll need to handle the InterruptedException and such.)

Answer 4

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.JFrame;
import javax.swing.Timer;

public class TimerExample {
    Random rand = new Random();
    static int currRand;

    TimerExample() {
        currRand = rand.nextInt(99);
        ActionListener actionListener = new ActionListener() {
            public void actionPerformed(ActionEvent actionEvent) {
                currRand = rand.nextInt(99);
            }
        };
        Timer timer = new Timer(2000, actionListener);
        timer.start();
    }

    public static void main(String args[]) throws InterruptedException {
        TimerExample te = new TimerExample();
        while( true ) {
            Thread.currentThread().sleep(500);
            System.out.println("current value:" + currRand );
        }
    }
}

EDIT: Of course you should set 2000 in new Timer(2000, actionListener); to 120 000 for two minutes.

Answer 5

I'm not entirely sure I understand the problem. If you wish to generate a different random number every two minutes, simply call your rnd function every two minutes.

This could be as simple as something like (pseudo-code):

n = rnd()
repeat until finished:
    use n for something
    sleep for two minutes
    n = rnd()

If you want to keep using the same random number for two minutes and generate a new one:

time t = 0
int n = 0

def sort_of_rnd():
    if now() - t > two minutes:
        n = rnd()
        t = now()
    return n

which will continue to return the same number for a two minute period.