OOP Intro Exercise 2

TimeAmount
Create a class that models an amount of time in hours, 
minutes, and seconds.

There are two constant variables:
+ SECONDS_PER_HR : int  (has the value 3600)
+ SECONDS_PER_MIN : int (has the value 60)

There are three data members:
+ hours : int
+ minutes : int
+ seconds : int

There are two methods. You determine if these are instance 
methods or class methods:
+ calculateTotalSeconds() : long
Calculates and returns the total number of seconds in the 
time amount.
+ displayTime() : String
Returns a formatted string for the time in the form HH:MM:SS
(tip: to add padding a 0 in front of the width e.g. use 
%02d to have 2 spots for digits and add a leading 0 if 
there's only 1 digit to display)

Test your TimeAmount class in a main() class: 
create an instance of the class and assign values to 
the hours, minutes, and seconds. 
Test your total seconds and display methods to make 
sure they work properly.

ANSWER this question inside comments above your constant 
declarations: Are the constants class members or instance 
members? How do you know?

CHALLENGE: add a method calculateDifference() that calculates 
and returns the difference in seconds between the current 
TimeAmount object and another TimeAmount object (pass the 
second time object into calculateDifference() as an 
argument/parameter).