虽然while循环似乎没有循环-循环中只有数学

Question

I can not figure out why my loop won't continue. Every time I run the program, it executes only one iteration of the loop.

I am implementing the algorithm based on mathematician Lewis Caroll where you remove the last digit from an input number and subtract it from the number formed by the remaining digits. For example, if I input the number 48070 the output is

48070
4807

and it stops there instead of continuing.

// The "Divisible_Dianik" class.
import java.awt.*;

public class Divisible_Dianik
{

    public static void main (String[] args)
    {
        int userinput = 1;
        int lastint;
        int firstpart;
        int output = 1;

        while (output != 0)
        {
            userinput = In.getInt ();
            lastint = userinput % 10;
            firstpart = userinput / 10;
            output = firstpart - lastint;
            System.out.println (output);
            userinput = output;
        }

    } // main method
} // Divisible_Dianik class

Answer 1

I'm going to assume that In.getInt() is some kind of abstraction for getting terminal-based feedback from the user. It's easily supplanted by this:

Scanner scan = new Scanner(System.in);
// in the loop
userinput = scan.nextInt();
scan.nextLine();

If this is the case, the reason you don't loop is due to this blocking for input every time. What you want to do is move the request for input outside of the loop.

int lastint;
int firstpart;
int output = 1;
Scanner scan = new Scanner(System.in);
int userinput = scan.nextInt();
while (output != 0) {
    lastint = userinput % 10;
    firstpart = userinput / 10;
    output = firstpart - lastint;
    System.out.println(output);
    userinput = output;
}