//
// simple example of threads in Java, showing (possible) interleaving 
//	of actions from two independent threads.  whether/how they are
//	interleaved depends on the scheduler in use and so may be
//	different on different systems.  
//
// see main method below for command-line arguments.
//

//
// a PingPong object, when executed by a thread, repeatedly 
//      prints message msg.
//
public class PingPong implements Runnable {

        String msg ;
        int cycles ;

        PingPong(String m, int c) {
                msg = m ;
                cycles = c ;
        }

        // implements run() in Runnable interface to define object's
        //      behavior.
        public void run() {
                for (int i = 0 ; i < cycles ; i++) 
                        System.out.println(msg) ;
        }

        // command-line arguments are integers S1, S2, C.
        // builds and starts two threads using PingPong
        //      objects, 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 < 1) {
                        System.out.println("Arguments are:") ;
                        System.out.println("  cycles") ;
                        System.exit(-1) ;
                }

                int C = Integer.parseInt(args[0]) ;

                Thread t1 = new Thread(
                        new PingPong("ping---->", C)) ;
                Thread t2 = new Thread(
                        new PingPong("<----pong", C)) ;

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