public class Test {

    public static int plukj = 0;
    public static void main(String[] args){
        final long startTime = System.currentTimeMillis();

        Thread a = new Thread(){
            public void run(){
            while(System.currentTimeMillis() < startTime + 20000){
                plukj++;
                System.out.println(plukj + " Adding");
            }
            System.out.println("FINISHEDA");
            }
        };
        Thread b = new Thread(){
            public void run(){
            while(System.currentTimeMillis() < startTime + 20000){
                plukj--;
                System.out.println(plukj + " Substracting");
            }
            System.out.println("FINISHEDB");
            }
        };
        a.start();
        b.start();
    }

}