What is a complex number?
What are the essential parts of a complex number? How can these
be represented as fields in a ComplexNumber class?
Is this the only way to represent a complex number?
What should the constructor for a ComplexNumber
look like?
Do you need any get() or set()
methods? (Can a complex number change its state or should it be
immutable?)
What do you want to do with a complex number? What methods should you write?