public class ThreadUse2 implements Runnable {
    public int id = 1;

    public static void main(String[] args) {
        ThreadUse2 tr = new ThreadUse2();
        Thread t1 = new Thread(tr);
        Thread t2 = new Thread(tr);
        Thread t3 = new Thread(tr);
        t1.start();
        t2.start();
        t3.start();
    }

    public void run() {
        while (id <= 20) {
            System.out.print(id + "   ");
            Thread.yield();
            id++;
        }
    }
}