advice sampling thread

[Karsten Daemen]

Hi

situation:
I'm currently working with some fellow students on a "school" project involving Lego Mindstorms. We're using Lejos to run java programs on the Lego robot.

Through Libraries we have an object 'sensor' that updates a variable every 20 ms. I can read this variable using the method 'readValue()'. I've written the following thread to sample this sensor at 20ms:

public class TestThread extends Thread {

  private boolean finished = false;
  private Sensor sensor = new Sensor();

  public void run () {

   while(!this.finished) {

     int value = this.sensor.readValue();
     doSomething(value);

     try {
       Thread.sleep(20);
      } catch (InterruptedException e) {
        e.printStackTrace();
      }

    }
  }

  public void kill() {
     this.finished = true;
  }

}
 

problem
Our mentor however, isn't happy with the "Thread.sleep(20)" method we're using to achieve the sampling effect (because of the inaccuracy of the sleep method). He hinted that there was a better way to do this. Could you suggest some other better method or at least give me a hint in which direction to search? I'm very ill experienced in Threads.

Thanks in advance for your advice!

[Tom Reilly]

How about using some kind of Timer or StopWatch class?

BTW, you should declare your finished variable as volatile.

[Karsten Daemen]

Thanks I'll look in to that!

After I looked it up, 'finished' should be indeed volatile.

[Steve Luke]

Given your mentor's concern over the accuracy of the sleep timer, I am not sure the Timer, or a stop watch would be any better. Does the leJos tutorial provide an alternate to polling?

[hint] yes ;-) [/hint]

[Karsten Daemen]

Thanks Steve, that was exactly what I'm looking for! I was searching in the wrong direction, it has nothing to do with the threat architecture, just a simple Listener suffices.

Moral of this Topic:
Read the damn documentation!

Again thanks!