// a stopwatch class used to measure time
public class Stopwatch {
    
    // time when the stopwatch was started
    private double startTime;
    
    public Stopwatch() {
      startTime = System.currentTimeMillis();  
    }
    
    public double getElapsedMilliseconds() {
        return System.currentTimeMillis() - startTime;
    }
    
    public double getElapsedSeconds() {
        return this.getElapsedMilliseconds() / 1000;
    }
    
    public void reset() {
        startTime = System.currentTimeMillis();
    }

}