Writing a program with 2 threads which prints alternatively

Question

I got asked this question recently in an interview.

Write a program with two threads (A and B), where A prints 1 , B prints 2 and so on until 50 is r

Answer 1

package thread;

public class Pingpong extends Thread {
    static StringBuilder object = new StringBuilder("");
    static int i=1;

    @Override
    public void run() {
        working();
    }
    void working() {
        while (i<=10) {
            synchronized (object) {
                try {
                    System.out.println(Thread.currentThread().getName() +"  "+ i);
                    i++;
                    object.notify();
                    object.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Pingpong();
        Thread t2 = new Pingpong();
        t1.setName("Thread1");
        t2.setName("Thread2");
        t1.start();
        t2.start();
    }
}

Thread1  1
Thread2  2
Thread1  3
Thread2  4
Thread1  5
Thread2  6
Thread1  7
Thread2  8
Thread1  9
Thread2  10