The folder Timer has all project files.
call_back_1 and call_back_2 are the two interfaces.
call_back_1 has function onSecondsUpdate(ClockTimer remainingTime)
call_back_2 has function onTimerEnd()
ClockTimer class uses the interfaces and has the properties of stopwatch
ClockTimerUse is the class that uses ClockTimer class for testing the working of ClockTimer