That's hogwash. Dr. Paul Backes, Technical Group Leader at Jet Propulsion Lab:

In 2001 and beyond, scientists will use Java to relay command sequences to a remote rover on Mars, just as schoolchildren and other Internet visitors are doing in the simulation today. But will Java ever be embedded in the actual devices deployed to outer space? "Yes, I can imagine using Java for rovers and spacecraft," says Paul. "I think it is inherently a safer language than C and C++, which is very important for spacecraft."