If we need to show countdown till in some point of time in future then CountDown timer is the best solution

CountDown Timer sets countdown till in some point of time in the future, with regular interval.

CountDownTimer is the class that handles all this.

Below is the code that shows countdown on a TextView

 new CountDownTimer(30000, 1000) {

     public void onTick(long millisUntilFinished) {
         mCountDownText.setText("Remaining seconds: " + millisUntilFinished / 1000);
     }

     public void onFinish() {
         mCountDownText.setText("done!");
     }
  }.start();

Now we need to show timer in HH:MM:SS format.

So need to convert the long value to hours, min and second simple.

I am doing it using TimeUnit that represents time durations at a given unit of granularity and extents Enum<TimeUnit>

So Below is the modified code.

 new CountDownTimer(100000, 1000) {
                                                        @Override
                                                        public void onTick(long millisUntilFinished) {


                                                          String timerValue =   String.format("%02d:%02d:%02d",
                                                                    TimeUnit.MILLISECONDS.toHours(millisUntilFinished),
                                                                    TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished) -
                                                                            TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(millisUntilFinished)), // The change is in this line
                                                                    TimeUnit.MILLISECONDS.toSeconds(millisUntilFinished) -
                                                                            TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished)));

                                                            String timerValue1 = String.format("%02d:%02d:%02d", TimeUnit.MILLISECONDS.toHours(millisUntilFinished),
                                                                    TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished) - TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(millisUntilFinished)),
                                                                    TimeUnit.MILLISECONDS.toSeconds(millisUntilFinished) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(millisUntilFinished)));
                                                            System.out.println(hms);
                                                            mTimerButton.setText(timerValue1);
                                                        }

                                                        @Override
                                                        public void onFinish() {
                                                         mTimerButton.setText("done!");
                                                        }
                                                    }.start();