The join() method of Thread Class in Java

The join function −

The join method makes sure that the current thread waits until the thread it is supposed to join with has been terminated. This function waits until the thread on which the function was called, has been terminated.

Syntax

final void join() throws InterruptedException

Let us see an example −

Example

public class Demo extends Thread{
   public void run(){
      System.out.println("sample ");
      try{
         Thread.sleep(10);
      }
      catch (InterruptedException ie){
      }
      System.out.println("only ");
   }
   public static void main(String[] args){
      Demo my_obj_1 = new Demo();
      Demo my_obj_2 = new Demo();
      my_obj_1.start();
      System.out.println("The first object has been created and started");
      try{
         System.out.println("In the try block, the first object has been called with the join          function");
         my_obj_1.join();
      }
      catch (InterruptedException ie){
      }
      System.out.println("The second object has been started");
      my_obj_2.start();
   }
}

Output

The first object has been created and started
In the try block, the first object has been called with the join function
sample
only
The second object has been started
sample
only

A class named Demo extends the Thread class. Here, a ‘run’ function is defined wherein a try catch block is defined. Here, in the try block, the sleep function is called and the catch block is left empty. In the main function, two instances of the Demo object are created. The first object is stated and it is called using the ‘join’ function. The same is done with the second object as well and messages are relevantly displayed.