thread join java

1class ThreadJoining extends Thread 
2{ 
3    @Override
4    public void run() 
5    { 
6        for (int i = 0; i < 2; i++) 
7        { 
8            try
9            { 
10                Thread.sleep(500); 
11                System.out.println("Current Thread: "
12                        + Thread.currentThread().getName()); 
13            } 
14  
15            catch(Exception ex) 
16            { 
17                System.out.println("Exception has" + 
18                                " been caught" + ex); 
19            } 
20            System.out.println(i); 
21        } 
22    } 
23} 
24  
25class GFG 
26{ 
27    public static void main (String[] args) 
28    { 
29        ThreadJoining t1 = new ThreadJoining(); 
30        ThreadJoining t2 = new ThreadJoining(); 
31        ThreadJoining t3 = new ThreadJoining(); 
32        t1.start(); 
33        try
34        { 
35            System.out.println("Current Thread: "
36                  + Thread.currentThread().getName()); 
37            t1.join(); 
38        } 
39        catch(Exception ex) 
40        { 
41            System.out.println("Exception has " + 
42                                "been caught" + ex); 
43        } 
44        t2.start(); 
45        try
46        { 
47            System.out.println("Current Thread: "
48                 + Thread.currentThread().getName()); 
49            t2.join(); 
50        } 
51        catch(Exception ex) 
52        { 
53            System.out.println("Exception has been" + 
54                                    " caught" + ex); 
55        } 
56        t3.start(); 
57    } 
58}