package com.company;
import java.util.*;
public class ExerciseB {
  public static void main(String[] args) {
    while (true) {
        System.out.println("Enter a digit or 'quit' to quit: ");
        Scanner userInput = new Scanner(System.in);
        if (userInput.hasNextInt()) {
            int intInput = userInput.nextInt();
            int i;
            int intCharSquare;
            ArrayList<Integer> valueCharSquare = new ArrayList<>();
            // Generating the square of each character of the inputted integer and adding it to the valueCharSquare ArrayList
            String stringOfIntInput = String.valueOf(intInput);
            for (i = 0; i <= stringOfIntInput.length() - 1; i++) {
                intCharSquare = (int) Math.pow((int) stringOfIntInput.charAt(i), 2);
                valueCharSquare.add(intCharSquare);
            }
            
            // Storing the first value of the valueCharSquare ArrayList into a variable
            int result = valueCharSquare.get(0);
            // Converting the value of result into a string
            String.valueOf(result);
            /* Obtaining the other values of the valueCharSquare ArrayList
             * and storing them into otherResult variable
             * then converting otherResult into a string
             * then concatenating the values of result and otherResults
             */
            for (i = 1; i <= valueCharSquare.size() - 1; i++) {
                int otherResults = valueCharSquare.get(i);
                String.valueOf(otherResults);
                result = result + otherResults;
            }
            
            // Printing out the new value of result
            System.out.println(result);
        // This happens if the user input is a string
        } else if (userInput.hasNext()) {
            String stringInput = userInput.nextLine();
            if (stringInput.equals("quit")) {
                break;
            } else {
                continue;
            }
        }
    }
  }
}

static String squareDigits(int number) {
String numberString = Integer.toString(number);
StringBuilder buf = new StringBuilder();
if (number < 0)
buf.append('-');
for (int i = (number < 0 ? 1 : 0); i < numberString.length(); i++) {
int digit = Character.digit(numberString.charAt(i), 10);
buf.append(digit * digit);
}
return buf.toString();
}

System.out.println(squareDigits(13579));       // 打印：19254981
System.out.println(squareDigits(-2468));       // 打印：-4163664
System.out.println(squareDigits(0));           // 打印：0
System.out.println(squareDigits(1999999999));  // 打印：1818181818181818181