Refer to the JOP wiki for some general background and starting material: http://www.jopwiki.com/Getting_started

cd jop/
make tools
cd asm/
sh jopser.sh

cd ../xilinx/nexys2/
ise jop.xise

Then synthesise, implement, create a bit file and program it onto the board. You could also use one of the pre-provided BIT files in the Downloads link above.

cd ../../
make java_app P3=NexysTest

Now you can download the image java/target/dist/bin/NexysTest.jop via serial using the down_posix app:

gcc -o down_posix ./c_src/down_posix.c
./down_posix -usb -e java/target/dist/bin/NexysTest.jop /dev/ttyS0

After it finishes, you should see the LEDs scanning back and forth while the 7seg increments once per second. Also, the current time should print out on the serial console.

The code causing this demo to happen is in java/target/src/test/test/NexysTest.java