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Thread: calculate sum and product

  1. #1
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    Default calculate sum and product

    The program is supposed to calculate the sum of number 1-5 and calculate the product of number 1-5. This is my code:

    package homeworktest;
     
    /**
     *
     * @author user
     */
    public class HomeworkTest {
     
        /**
         * @param args the command line arguments
         */
        public static void main(String[] args) {
            int count = 0;
            int sum = 0;
            int product = 0;
            do
            {
                count++;
                sum += count;
                product *= count;
                if (count == 5)
                    System.out.println("Sum = " + sum);
                    System.out.println("Product = " + product);
            } while (count < 5);
                    } //end main
     
     
            }
    This is the output I get:
    run:
    Product = 0
    Product = 0
    Product = 0
    Product = 0
    Sum = 15
    Product = 0
    Last edited by helloworld922; September 26th, 2011 at 06:06 PM.


  2. #2
    Administrator copeg's Avatar
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    Default Re: calculate sum and product

    For future reference, please wrap your code in the [highlight][/highlight] tags.

    I suggest writing down the math on a piece of paper, going through the algorithm the code executes a step at a time. As hint, 0 time anything will still be zero.

  3. #3
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    Default Re: calculate sum and product

    Ugh, sorry, I still don't get it.

  4. #4
    Super Moderator helloworld922's Avatar
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    Default Re: calculate sum and product

    In your code:
    int product = 0;
    And later on:
    product *= count;

    0*1 = ?
    0*2 = ?
    0*3 = ?
    ...

  5. #5
    Think of me.... Mr.777's Avatar
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    Default Re: calculate sum and product

    I hope you already have the answer now. No need to explain here though any better than helloworld922 and copeg.

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: calculate sum and product

    One other thing about your coding style, indenting a statement does NOT make it be inside of the if statement's block. If you look at the printout from your code you will see a repeated printout. Did you expect that?
    You should ALWAYS use {}s to delimit the statements following if, else, while etc.
    90% of the time that you don't, it causes an error when you try to add another statement.

  7. #7

    Default Re: calculate sum and product

    A tip:
    Whenever initializing a variable to keep track of a product, initialize it to the first entry or factor.

    //do not do this
    int product = 0;
    product *= intArray[0];
    product *= intArray[1];
    product *= intArray[2];
    ...
     
    //do this
    int product = intArray[0];
    //or
    int product = 1;

    Also:
    if (count == 5)
                    System.out.println("Sum = " + sum);
                    System.out.println("Product = " + product);
    Java allows syntax for using the if statement implicitly with no braces, but only one statement following the if clause is counted in the implied "then" clause. If you use braces, you are being explicit and explicit is better.
    Kenneth Walter
    Software Developer
    http://kennywalter.com

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