xcode porting question

I was talking with a few people i know, and they were saying to use java and obj-c for the gui and compile it all together so the java cant be decompiled, im considering that but i did alittle research and i cant seem to find anything about porting to windows, or linux, is there a way to compile for all 3 systems from xcode? I haven;t yet began to work with xcode. Another question, if i developed a game in C could compile it for windows and linux from mac with xcode or how would that work? im trying to find the best programming language thats fast in performace and creating but be able to make it platform independent at the same time, i was looking at realbasic but decided not to do it with realbasic, i dont really want to do it in java unless i can compile with a obj-c front end for all 3 systems. Is my last option C and develope it in myeclipse and just manually compile it for all 3 systems?