Question

Divisibility by 9

To determine if a number is evenly divisible by 9, simply add all of the digits in that number. If the sum is divisible by 9, then the original number also is divisible by 9.

For example, notice that all of the multiples of 9 from 1 through 12 (9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, and 108) contain digits which sum to 9 or 18 in every case.

In another example, to determine if the number 544,293 is divisible by 9, add all of the digits in that number (5 + 4 + 4 + 2 + 9 + 3) which totals 27. Since 27 is divisible by 9, then so is 544,293.

In this part of the lab, write a program which does the following:

1. Prompt the user for a whole number and read the user’s input into a String.
2. Calculate the sum of the digits in the number by looping through each character (each digit) in the String, converting it to a number, and adding it to the sum.
3. If the sum of the digits is 0, then exit the program
4. Otherwise, determine if the sum of the digits in the number is evenly divisible by 9.
5. Using that result, print a message to the user indicating whether or not the original number is divisible by 9.
6. Go back to step 1.

Notice that this process has a way to stop (step 3 above), and that each step is well-defined and unambiguous, so this process satisfies our definition of an algorithm.

Submit a listing of your program, along with a PrintScreen showing what happens when you enter the following numbers: 9, 54, 84023, 333333, and the sentinel 0.

Answer 1

import java.util.Scanner;

public class DivisibleBy9 {
  
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
String inp = "";
  
do
{
int sum = 0;
System.out.print("Enter a whole number: ");
inp = sc.nextLine().trim();
if(inp.equals("0"))
{
System.out.println("Sum of digits is 0..exiting program");
System.exit(0);
}
  
for(int i = 0; i < inp.length(); i++)
{
int digit = Character.getNumericValue(inp.charAt(i));
sum += digit;
}

if(sum == 0)
{
System.out.println("Sum of digits is 0..exiting program");
System.exit(0);
}
else
{
if(sum % 9 == 0)
System.out.println(inp + " is completely divisible by 9");
else
System.out.println(inp + " is not completely divisible by 9");
}
}while(!inp.equalsIgnoreCase("0"));
}
}

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