J-DOS provides and integrated JAVA environment for the execution of a program across an interconnected network of heterogeneous computers. The system provides a file system, shared memory and a distributed execution scheme, all of which is transparent to the user. The framework used to provide these service is sufficiently general as to allow the provision of extra services by the user. We describe the client-server execution, remote execution and the shared file system, paying particulat attention to the techniques used to distribute threads over many nodes. Distributed Mandelbrot set generation and rendering is used to benchmark and validate the the remote execution and load balancing aspects of the system.