Robot Simulation in Java

I am doing a project concerning robot simulation and i need help. I have to simulate the activities of a robot in a warehouse. I am using mindstorm robots and lego's for the warehouse. The point here is i have to simulate all the activities of the robot on a Java GUI. That is whenever the robot is moving, users have to see it on the GUI a moving object which represents the robot. When the roads/rails/crossings of the warehouse changes it must also be changed on the screen. The whole project is i have to simulate whatever the robot is doing in the warehouse in real-time. Everything must happen in real-time I am asking which libraries in Java i can use to do this simulations in real-time and if someone can also point me to any site for good information. Am asking for libraries in Java that i can use to visualize the simulation in real-time.