Why does my while loop not work for counting the sum of an array and displaying the array

Question

I am attempting to display a random array whilst also displaying the sum of that array yet I can't get it to work, I know how to do it with a for loop but I was instructed on doing a while loop instead, any ideas?

 private void SumOfArray() {
        myWindow.clearOut();
        int total = 0;
        int[] a = new int[4];
        int i;
        i = 0;
        while (i < a.length) {
            i++;
            a[i] = 1 + (int) (Math.random() * 10);
        }
        i = 0;
        while (i < a.length) {
            i++;
             myWindow.writeOutLine(a[i]);
        }
        while (i < a.length) {
            total += a[i];
        i++;

        }
        myWindow.writeOutLine(total);

    }

What does the output give you? What were you expecting instead? I know this problem is simple but it's good to be specific and say exactly what the problem is. — markspace
– markspace, Commented Apr 19, 2016 at 13:18

Eran · Accepted Answer · 2016-04-19 13:18:17Z

6

You are incrementing i prematurely, causing an ArrayIndexOutOfBoundsException. You should increment it after assigning a number of a[i].

Change it to

    while (i < a.length) {
        a[i] = 1 + (int) (Math.random() * 10);
        i++;
    }

Now the loop behaves similar to a for loop - i.e. i is incremented after all the other statements of the loop's body.

Your other loops should also be fixed, and in fact, all your loops can be merged into a single loop :

    int i = 0;
    while (i < a.length) {
         a[i] = 1 + (int) (Math.random() * 10);
         myWindow.writeOutLine(a[i]);
         total += a[i];
         i++;
    }

answered Apr 19, 2016 at 13:18

Eran

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Comments

Sharon Ben Asher · Accepted Answer · 2016-04-19 13:22:31Z

1

in addition, You have 3 while loops and two times where you assign 0 to i ....

answered Apr 19, 2016 at 13:22

Sharon Ben Asher

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