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Thread: Java program to write a code to detect divisibility of any number by 11

  1. #1
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    Default Java program to write a code to detect divisibility of any number by 11

    Introduction to my problem:

    I have to code a program that ask for the user to enter a positive integer and then I have to find if the value that was enter is divisible by 11 (with no remainder) and display "yes" if it is divisible and "no" if it is not.

    However, the method that I have to use to determine if the enter value is divisible by 11 (with no remainder) is by using a certain method demonstrated below:

    For example suppose that n=9343752, then t=2-5+7-3+4-3+9==11. 11 is
    divisible by 11 then it follows that 8784204 is divisible by 11.

    If n=843439 then t=9-3+4-3+4-8=3. 3 is not divisible by 11 then
    843439 is not divisible by 11.

    if the user enter's a non postive integer the program should continue asking for a positive value until
    the user does so.

    My code so far:

    My code below accepts only 10-digit integers and I have struggled for it to accept any postive integers. It will not run if enter a negative 10-digit integer.


    [FONT=Arial Black][SIZE=2]public class DivisionBy11{
    public static void main(String[] args) throws IOException{
    InputStreamReader in = new InputStreamReader(System.in);
    BufferedReader br = new BufferedReader(in);
    System.out.println("Please enter a positive integer");
     
    String numbers = br.readLine();
    while( Keyboard.ReadInt() <0){[COLOR=Lime]  /*I'm try to check if the enter value is a positive integer and if it's not, to prompt the user to enter a positive integer. So I've been unsuccessful.*/[/COLOR]:(
     
        System.out.println("Please enter a positive integer");
     
    }
     
    String numbers1 = numbers.substring(9,10);
    String numbers2 = numbers.substring(8,9);
    String numbers3 = numbers.substring(7,8);
    String numbers4 = numbers.substring(6,7);
    String numbers5 = numbers.substring(5,6);
    String numbers6 = numbers.substring(4,5);
    String numbers7 = numbers.substring(3,4);
    String numbers8 = numbers.substring(2,3);
    String numbers9 = numbers.substring(1,2);
    String numbers10 = numbers.substring(0,1);
    int numberi1 = Integer.parseInt(numbers1);
    int numberi2 = Integer.parseInt(numbers2);
    int numberi3 = Integer.parseInt(numbers3);
    int numberi4 = Integer.parseInt(numbers4);
    int numberi5 = Integer.parseInt(numbers5);
    int numberi6 = Integer.parseInt(numbers6);
    int numberi7 = Integer.parseInt(numbers7);
    int numberi8 = Integer.parseInt(numbers8);
    int numberi9 = Integer.parseInt(numbers9);
    int numberi10 = Integer.parseInt(numbers10);
    System.out.println("The number was " + numbers);
    float t = 0;
    float n=0;
    int myvalue = 0;
    t = numberi1 - numberi2 + numberi3 - numberi4 + numberi5 - numberi6 + numberi7 - numberi8 + numberi9 -
            numberi10;
    System.out.println(t);
    n = t / 11;
     
    if(Math.round(n)==myvalue){ [COLOR=Lime]//I'm having difficulty in check the return value is an integer[/COLOR]:-ss
        System.out.println("Yes");
    }
        else
            System.out.println("No");
     
     
        }
     
    }[/SIZE][/FONT]

    Any help will be greatly appreciated.
    Last edited by Deep_4; November 8th, 2012 at 01:35 PM.


  2. #2
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: My Division Problem

    import java.util.Scanner;
     
     
    public class DivideBy11 {
    	public static void main(String[] args){
    		int inputNumber;
     
    		System.out.println("Enter a positive number: ");
    		while((inputNumber = new Scanner(System.in).nextInt()) < 0);
     
    		String tempNumber = Integer.toString(inputNumber);
    		int total = 0;
    		boolean add = true;
     
    		for(int i = tempNumber.length() - 1; i >= 0; i--){
    			if(add){
    				total += (tempNumber.charAt(i)-48);
    				add = false;
    			}else{
    				total -= (tempNumber.charAt(i)-48);
    				add = true;
    			}
    		}
     
    		if(total == 11){
    			System.out.println("Yes.");
    		}else{
    			System.out.println("No.");
    		}
    	}
    }

    Chris
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  3. #3
    Super Moderator helloworld922's Avatar
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    Default Re: My Division Problem

    Have you heard of the mod operator, as well as the parseInt method? Scanner also has a nextInt methd.
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a number: ");
    int num = input.nextInt();
    if (num % 11 == 0)
    {
         System.out.println(num + " is divisible by 11");
    }
    else
    {
         System.out.println(num + " has a remainder of " + (num%11) + " when divided by 11");
    }

  4. #4
    Senile Half-Wit Freaky Chris's Avatar
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    Default Re: My Division Problem

    i was guessing it was a challenege set, where they cannot use mod to determine it
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  5. #5
    Super Moderator helloworld922's Avatar
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    Default Re: My Division Problem

    calculate the remainder by hand (not completely sure how numerically stable this is, but in theory it works)
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a number: ");
    double num = input.nextInt();
    if (num - (11 * Math.floor(num/11)) == 0)
    {
         System.out.println(num + " is divisible by 11");
    }
    else
    {
         int remainder = (int)(num - 11 * Math.floor(num/11));
         System.out.println(num + " has a remainder of " + remainder + " when divided by 11");
    }
    Last edited by helloworld922; August 8th, 2009 at 12:52 PM.

  6. The Following User Says Thank You to helloworld922 For This Useful Post:

    Java'88 (August 16th, 2009)

  7. #6
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    Default Re: My Division Problem

    Thank very very much for your help Freaky Chris and hellooworld922.

    Quote Originally Posted by Freaky Chris View Post
    i was guessing it was a challenege set, where they cannot use mod to determine it
    Yes, mod operater was not allowed, thats what made this challenge really difficult for me.

    The method below had to be use as that is what the challenge ask for.

    Method:
    E.g. n=9343752, then t=2-5+7-3+4-3+9==11. 11 is
    divisible by 11 then it follows that 8784204 is divisible by 11.

    Quote Originally Posted by helloworld922
    Have you heard .... parseInt method? ..Scanner also has a nextInt methd.
    I have not yet reach the parseInt and Scanner method in my Java for Dummies, 4th edition

    Freaky Chris would example to me how this part of your code works, as I did not understand fully what is happening here.


    Thank you.

    JAVA CODE
    ...
    if(add){
    total += (tempNumber.charAt(i)-48);
    add = false;
    }else{
    total -= (tempNumber.charAt(i)-48);
    add = true;
    }

    ...

  8. #7
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    Default Re: My Division Problem

    subractign 48 from the character representation of anumber gives you the numerical value of it for example, '1'-48 = 1 if that makes sense

    Chris
    chris[at]javaprogrammingforums[dot]com

    Prifysgol Bangor University, North Wales

  9. The Following User Says Thank You to Freaky Chris For This Useful Post:

    Java'88 (August 16th, 2009)

  10. #8
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    Default Re: My Division Problem

    Quote Originally Posted by Freaky Chris View Post
    subractign 48 from the character representation of anumber gives you the numerical value of it for example, '1'-48 = 1 if that makes sense

    Chris
    Yes, that make sense for me, Thanks

  11. #9
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    Default Re: My Division Problem

    Yeah I agree that mod should not be used, because that is what assignment was all about.

    Acumen
    Lucid forums