Standard Input
Programs are pretty boring if they just make a machine warm and do some math.
There are a lot of ways to make a program interactive, but the easiest is to read from what is called "standard input."
This function will be added to Java in a future version, but until then copy paste this at the very top of all the code in this section.
import java.util.Scanner;
Scanner scanner = new Scanner(System.in);
String input(String message) {
System.out.print(message);
return scanner.nextLine();
}