Hi guys, how can i sum number from the user input. For example if user input is "456" the output(system print) would be "15" (4+5+6). How can i do that?

i already have this following code:

import java.io.*;
public class Sum
public static void main(String[]args)throws IOException
BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter an integer between 0 and 999: ");
int number = Integer.parseInt(keyboard.readLine());