Question

I am going to simulate a traffic light system.
I created the Road Class which extends JFrame and implements Runnable.

Inside the run() method I added the logic to increase the Y Position of each car and It is now simulating the movements of cars.
But now I need to check the status of the Traffic Light, before move a car.

This is my TrafficLight class,

import java.util.Random;

public class TrafficLight implements Runnable {

volatile boolean stop;

public TrafficLight(boolean stop) {
    this.stop = stop;
}

@Override
public void run() {
    Random randomGenerator = new Random();
    while (true) {
        if (stop) {
            stop = false; //change current status
        } else {
            stop = true;  //change current status
        }
        try {
            Thread.sleep(2000 + randomGenerator.nextInt(2000));
        } catch (Exception ex) {
            System.out.println("error");
        }
       }
   }
}

Is there any way to check this volatile variable stop, from my Road Class.

If not please suggest me another solution to do this.

Thanks.

Answer 1

Implement an accessor for stop.

public class TrafficLight implements Runnable {

   volatile boolean stop;

   // Irrelevant code

   public boolean isStop() {
     return stop;
   }
}

Receive the TrafficLight on the Road class constructor and use it to get access to the stop variable

public class Road implements Runnable {

   private TrafficLight trafficLight;

   public Road (TrafficLight trafficLight) {
     this.trafficLight = trafficLight;     
   }

   @Override
   public void run() {
     // Irrelevant code
     if(trafficLight.isStop()) {
       // do something
     } 
   }
}