In building any software probject, you need to make lots of decisions as to how to design your system. It makes sense to think about these things before you actually start coding - it will save you lots of time in the long run. The design document should contain the following information:
Descriptions of the classes you will need to solve the problem, including variables and methods (private and public)
Headers for the methods that you will need
Descriptions of the purpose for each method
Descriptions of the variables, arrays, etc. you will need to store and manage the information
Estimates of how long it will take you to write each of these methods. Consider how long it will take to translate the pseudocode into actual Java code, then remember to leave lots of time for debugging and testing.
Your test plan: how will you test each of these methods individually to make sure they work?
You should plan on getting each of your classes to function independently. Among the many benefits of this approach is the constant availability of a partial solution that can be handed in for grading, or demonstrated to a customer, or released to the public for early testing.
Good luck!