Java: Add all the digits of a given positive integer until the result has a single digit

Last update on February 20 2025 11:44:03 (UTC/GMT +8 hours)

Sum Digits to Single Digit

Write a Java program to add all the digits of a given positive integer until the result has a single digit.

Pictorial Presentation:

Sample Solution:

Java Code:

import java.util.Scanner;

public class Example108 {
    public static void main(String[] arg) {
        // Create a Scanner object for user input
        Scanner in = new Scanner(System.in);

        // Prompt the user to input a positive integer
        System.out.print("Input a positive integer: ");
        
        // Read the user's input as an integer
        int n = in.nextInt(); 

        if (n > 0) {
            // Check if n is a positive integer
            System.out.print("The single digit number is: " + (n == 0 ? 0 : (n % 9 == 0 ? 9 : n % 9)));
        }
        
        // Close the input scanner
        in.close();
        System.out.println("\n");  
    }
}

Sample Output:

Input a positive integer: 25                                           
The single digit number is: 7

Flowchart:

For more Practice: Solve these Related Problems:

• Modify the program to find the digital root using modulo operations.
• Write a program to compute the sum of squares of digits until a single digit is reached.
• Modify the program to find the product of digits instead of sum.
• Write a program to return the number of steps required to reach a single digit.

Java Code Editor:

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