Yeah I thought you were spoon feeding because you posted a useless amount of code, I edited my post when I looked at the thread owner.
As a side rant, I really hate it when people say "I can't use that.. I'm just a beginner" because... well that seems counter-intuitive. Is your teacher actually going to give you points off
or do you think that there must be some simpler way to do this? If you really can't do arrays, than you can try to append a String like Kevin already said.
To append Strings you can use += (Compiler will automatically convert it to a StringBuilder, most likely)
String result = "";
int sum = 3;
result += sum+" ";
sum += 2;
result += sum + " ";