//
// simple example of threads in Java, showing interleaving of actions
//      from two independent threads
//
// in this version, thread objects are created using a subclass of
//      the Thread class (compare with SimpleThreadObj.java, which 
//      behaves the same but is implemented slightly differently).
//
// see main method below for command-line arguments.
//

//
// a SimpleThread object repeatedly prints message msg and then
//      sleeps for sleepIntvl milliseconds.
//
public class SimpleThread extends Thread {

        String msg ;
        long sleepIntvl ;
        int cycles ;

        SimpleThread(String m, int s, int c) {
                msg = m ;
                sleepIntvl = (long) s ;
                cycles = c ;
        }

        // overrides run() in Thread class to define object's
        //      behavior.
        public void run() {
                try {
                        for (int i = 0 ; i < cycles ; i++) {
                                System.out.println(msg) ;
                                sleep(sleepIntvl) ;
                        }
                // can safely ignore interrupts here -- should not
                //      happen in this program
                } catch (InterruptedException e) {
                }
        }

        // command-line arguments are integers S1, S2, C.
        // builds and starts two threads of type SimpleThread, with 
        //      sleep intervals of S1 and S2.  observe the difference
        //      in execution behavior when S1 and S2 are the same and
        //      when they are different.
        // continues for C cycles.

        public static void main(String[] args) {

                if (args.length < 3) {
                        System.out.println("Arguments are:") ;
                        System.out.println("  sleep interval for t1") ;
                        System.out.println("  sleep interval for t2") ;
                        System.out.println("  cycles") ;
                        System.exit(-1) ;
                }

                int S1 = Integer.parseInt(args[0]) ;
                int S2 = Integer.parseInt(args[1]) ;
                int C = Integer.parseInt(args[2]) ;

                SimpleThread t1 = 
                        new SimpleThread("ping---->", S1, C) ;
                SimpleThread t2 = 
                        new SimpleThread("<----pong", S2, C) ;

                t1.start() ;
                t2.start() ;
        }
}