Java Programming

I've been working on this project for school, building a class which models cartesian coordinates and can also convert them to polar coordinates. After much work I have a working product with some time to spare. Theres a small amount of extra credit to be gained if i can use toString() methods to manipulate my results to be exactly to two decimal places.

I've been looking at the api documentation, which is what my teacher suggested, but its a little tough for a rookie like me to wade through. A point in the right direction or any help would be greatly apreciated.

Thanks in advance