Uses of Package
ants

Classes in ants used by ants
AntWorld
          The model for the ant simulation
Contains the field (2-D array) in which Ants and DoodleBugs live

Class Invariant: Nr of rows and columns in the gird are positive and do not change once initialized
Critter
          Critter is an abstract class from which Ants and DoodleBugs are derived
Class Invariant: row and column are non-negative, world is not null

No new methods may be added to the Critter class

You will need other instance variables to
a.