Program Java cara membuat "Jam Mundur"

Beri nama Program : timer

import java.text.DecimalFormat;

class timer {
  
    private Thread thread;
  
    public static void main(String[] args) {
        int J,M,D;
        J=2;
        M=30;
        D=40;
        DecimalFormat format = new DecimalFormat("00");
        while (true) {
            try
            {
                Thread.sleep(1000);
            }
            catch (InterruptedException e)
            {
                Thread.currentThread().interrupt();
            }
         
             if(J==0 && M==0 && D==0)
             {
                 System.out.println(J+"0:"+M+"0:"+D+"0");
                break;
            }      
         
           System.out.println(format.format(J)+ ":"+format.format(M)+":" + format.format(D));
         
            if(M != 0) {
                if(D == 0) {
                    M--;
                    D = 60;
                }
            } else {
                if(D == 0) {
                    D = 59;
                }
            }
         
            if(J !=0) {
                if(M == 0) {
                    J--;
                    M = 59;
                }
            } else {
                if(M == 0) {
                    M = 0;
                }
            }
         
            D--;
    }
    }
}