I had 2 restore my computer and now i cant use java?

Ok so i got a virus awhile back and my computer would turn on for 30 seconds and crash... so i went in and restored my computer to factory settings... i lost EVERYTHING now i can play java based games and what not but when i try to play minecraft or use RuneScape bots i ALWAYS get a message that says java.lang.illegalArguementException: input == null! or something along the lines