High Quality Content by WIKIPEDIA articles! leJOS is a firmware replacement for Lego Mindstorms programmable bricks. It currently supports the LEGO RCX brick and leJOS NXJ supports the NXT brick. It includes a Java virtual machine, which allows Lego Mindstorms robots to be programmed in the Java programming language. It is often used for teaching Java to first-year computer science students. The leJOS-based robot Jitter flew around on the International Space Station in December 2001.