"ComplexExample" contains the main method for this program.

It illustrates a series of uses of the Complex class for manipulating 
complex numbers.  The constructor is used to initialise "one" and
"i" and then the "add" and "multiply" methods are used to perform
calculations. 

Note how the methods return a new Complex object for their result.
An alternative would be for them to update the object that they
are invoked on.  What would be the advantages and disadvantages of
such a change?