Secure Input during Runtime/Afterwards

i have to write a simple program, which takes input from the keyboard and outputs it. But the input shouldn't simply be found in the memory during the runtime or after the program has been terminated . Is there some kind of liberay out there which could be helpful. I'm able to use Java or C++. Since my first search on google didn't help me i ask you guys. I dont want a complete solution just a hint in the right direction.

Thank you feng