Text based Random Artificial sim? Java

For my next project I need to create a artificial simulator which includes objects, food ect. I must print out a text based map which would randomly include food and objects in set places, and the life must be able to be added on after the map has been generated. I was just wondering how should I go about making the map. I know how to do 2d arrays to print out, but am unsure how to randomise the positions and density of the objects and food. Any help or advice would be appreciated:)