创建一个显示数字的数字总和的 Java 应用程序

Question

I am relatively new to Java and I'm currently learning while, do while and for loops. I want to create an application that displays the sum of the digits of a number using these concepts but I have no idea how. I previously created an application that displayed ONLY THE DIGITS of a number. Here it is.

int digit;
Scanner input = new Scanner(System.in);

do {
    System.out.println("Enter a positive integer: ");
    digit = input.nextInt();
} while (digit <= 0);
input.close();

String sdigit = digit + "";
for (int i = 0; i < sdigit.length(); i++){
    System.out.println(sdigit.charAt(i));
}

I'm trying to think of a possible way to expand on this program, but I have no idea why. Once again, this program is not what I need, what I need is somehow to sum the digits of a number using for or while loops. Thank you!

Answer 1

not much code has to be added for summing the digits :

First solution : using a substract with '0' character

int digit;
Scanner input = new Scanner(System.in);

do {
    System.out.println("Enter a positive integer: ");
    digit = input.nextInt();
} while (digit <= 0);
input.close();

String sdigit = digit + "";
int sum=0;       

for (int i = 0; i < sdigit.length(); i++){
    System.out.println(sdigit.charAt(i));
    sum = sum + (sdigit.charAt(i) - '0');
}

System.out.println("Sum is : "+sum);

Second solution : using Integer.parseInt which converts String to int :

int digit;
Scanner input = new Scanner(System.in);

do {
    System.out.println("Enter a positive integer: ");
    digit = input.nextInt();
} while (digit <= 0);
input.close();

String sdigit = digit + "";
int sum=0;
for (int i = 0; i < sdigit.length(); i++){
    System.out.println(sdigit.charAt(i));
    sum = sum + Integer.parseInt(sdigit.subString(i,i+1));
}

System.out.println("Sum is : "+sum);

Answer 2

int digit;
System.out.println("Enter a positive integer: ");
number= Integer.parseInt(System.console().readLine());

int sum=0;
int currDigit = 0;
while( number / 10 > 0) {
    currDigit  = number % 10; //fetching last digit
    System.out.println(currDigit);
    sum = sum + currDigit;
    number = number / 10;
}