import java.util.*;		// has Date
import java.text.*;		// has NumberFormat

// ---- class for timing execution -----------------------------------

public class Timer {

    // Returns elapsed seconds since start of program.
    public static double elapsedSeconds() {
	return ((double) (new Date()).getTime()) / 1000 ;
    }

    // Formats a double in a way suitable for values returned from
    //   elapsedSeconds():  4 decimal places, fixed-point form.
    public static String format(double t) {
	// For a more general and internationalizable approach, see
	NumberFormat nf = NumberFormat.getInstance();
	nf.setMaximumFractionDigits(4);
	return nf.format(t);
    }

    // A little main program to test the above method.
    public static void main(String[] args) {

	if (args.length < 1) {
		System.out.println("Usage:  " +
				   "java Timer sleepSeconds");
		System.exit(1);
	}
	int sleepTime = Integer.parseInt(args[0]);
	try {
	    System.out.println("sleep for " + sleepTime + " seconds");
	    double startTime = elapsedSeconds();
	    Thread.sleep(sleepTime * 1000);
	    System.out.println("time for one execution = " 
			       + format(elapsedSeconds() - startTime));
	    Thread.sleep(sleepTime * 1000);
	    System.out.println("time for two executions = " 
			       + format(elapsedSeconds() - startTime));
	}
	catch (InterruptedException e) {
	    System.out.println("Something odd happened!:  " + e);
	}

    }
}