Get the current time from the timer. If the clock is running it is derived from the current
system clock the start time stored in the timer class. If the clock is not running, then
return the time when it was last stopped.
Current time value for this timer in seconds
Reset the timer by setting the time to 0. Make the timer startTime the current time so new
requests will be relative now
Start the timer running. Just set the running flag to true indicating that all time requests
should be relative to the system clock.
Stop the timer. This computes the time as of now and clears the running flag, causing all
subsequent time requests to be read from the accumulated time rather than looking at the
boolean hasPeriodPassed(double period)
Check if the period specified has passed and if it has, advance the start time by that
period. This is useful to decide if it's time to do periodic work without drifting later by
the time it took to get around to checking.