Java Tutorial : CountDownLatch

CountDownLatch are used to control to flow of multiple running task. CDL delays the run time of tasks before the main thread is ran. Its simply a timer that counts down to zero and when timer hits zero the main thread is ran but during its count down it is also running other tasks .

import java.util.concurrent.CountDownLatch; 

public class countdown 
    public static void main(String args[])  
                   throws InterruptedException 

//       Creating CountDownLatch , there are 3 task being executed 
        CountDownLatch cdl = new CountDownLatch(3); 
//       Naming tasks and setting delay times 
//        1 second delay
        Task Task_One = new Task(1000, cdl,  "task 1"); 
//        5 second delay
        Task Task_Two = new Task(5000, cdl,  "task 2"); 
//        3 second delay 
        Task Task_Three = new Task(3000, cdl,   "task 3"); 

//       Starting tasks
        // The main task waits here
        // Main thread running 
        System.out.println(Thread.currentThread().getName() + 
                           " You have hacked the main frame!"); 
// What main thread does while waiting  
class Task extends Thread 
    private int dt; 
    private CountDownLatch cdl; 
    public Task(int dt, CountDownLatch cdl, 
                                    String name) 
        this.dt = dt; 
        this.cdl = cdl; 
    public void run() 
//           task ran complete print finished 
                            + " finished"); 
//        if not throw exception 
        catch (InterruptedException e) 
Output :
task 1 finished
task 3 finished
task 2 finished
main You have hacked the main frame!

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