RouletteWheel.java

import java.util.Random;
 
public class RouletteWheel {
    private final WheelObserver wheelObserver;    
    private long timeStartMs;   
    private final Random random = new Random();  
 
    public RouletteWheel(final WheelObserver wheelObserver) {
        this.wheelObserver = wheelObserver;
    }
 
    public void spin(final long timeStartMs) {
        this.timeStartMs = timeStartMs;
    }
 
    public void tick(final long timeMs) {
        if ((timeMs - timeStartMs) >= 20000)
        { 
           final int location = random.nextInt(37); 
           this.wheelObserver.stopped(location);
        }        
    }
}