What will be the output of the below java code using volatile keyword?

Problem statement: Given code is

1. public class Test extends Thread {
2. private volatile int i = 0;
3. public int getData() {
4. return i + 1;
5. }
6. public void run() {}
7. public static void main(String[] args) {
8. Test t1 = new Test();
9. t1.start();
10. System.out.println("First thread: " + t1.getData());
11. Test t2 = new Test();
12. t2.start();
13. System.out.println("Second thread: " + t2.getData());
14. Test t3 = new Test();
15. t3.start();
16. System.out.println("Third thread: " + t3.getData());
17. }
18. }

Output:
First thread: 1
Second thread: 1
Third thread: 1