Trying to understand Methods

Question

I have a code that asks for integer input and outputs the sum of the integer.
import java.util.Scanner;
public class Assignment3a {
  public static void main (String[]args){
    Scanner input = new Scanner (System.in);
    //declaration
    int i, n, mod=0, sum = 0;
    //get user input for 'How many inputs'
    System.out.print ("How many numbers in input? ");
    i = input.nextInt();
    //number of itterations
    for (int entry=1; entry <= i; entry++){
      System.out.print ("Enter a positive integer: ");
      n = input.nextInt();
      while (n < 0){//If number is negative
        System.out.print ("ERROR! Should be positive. Enter a positive integer: ");
        n=input.nextInt();
      while(n>0){//sum of integers
        mod= n % 10;
        sum= mod + sum;
        n = n / 10;}
      System.out.println ("The sum of digits is " + sum + ".");
      mod = 0;//reset integers
      sum = 0;
}What I need is to use a method which does the sum of digit part. Here is a vague idea, of what I think it would be. Obviously, there are several error. Would someone show me the right way?
import java.util.Scanner;
public class test {
  public static void main (String[]args){
    Scanner input = new Scanner (System.in);
    //declaration
    int i, n, mod=0, sum = 0;
    //get user input for 'How many inputs'
    System.out.print ("How many numbers in input? ");
    i = input.nextInt();
    //number of itterations
    for (int entry=1; entry <= i; entry++){
      System.out.print ("Enter a positive integer: ");
      n = input.nextInt();
      if (n < 0){//If number is negative
        System.out.print ("ERROR! Should be positive. Enter a positive integer: ");
        n=input.nextInt();
      else{//sum of integers
        displaySum(n,mod,sum);
        System.out.println (sum);
  public static void displaySum(int n, int mod, int sum){  
    mod= n % 10;
    sum= mod + sum;
    n = n / 10;
}Edited by: acastelino2001 on Apr 22, 2010 2:27 PM

Answer 1

acastelino2001 wrote:
I think you misunderstood me or may be I wasn't clear enough. the program should call a method (in this case displaySum) to solve the sum. The issue I'm having is, that I don't fully understand how methods work...Then it seems to me that you need to read the tutorials; otherwise anything we give you, while it might do the job, won't be your own work.
However, a method is essentially a named function which does a specific piece of work. It takes input in the form of parameters and hands back a result, in the form of a return value; however neither are absolute requirements (a method can have no parameters, and can define a return type of 'void', which indicates that it does not return a value).
The real craft of programming is to set up methods that break down the problem you've been assigned into single tasks, and for that reason I agree completely with flounder that calculateSum() is the first thing you should look at. Once you've got that working, you can then use its result to create a displaySum() method that prints it out.
Winston