使用矩形数组的简单嵌套for循环上的越界异常

Question

I have a simple nested for loop that outputs the results perfectly but then throws a:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4

The array is 4 rows and 4 columns, and I am trying to total the columns so I basically just reversed the nested loop.

        rowIndex = 1;
        for (int i = 0; i < regions[i].length; i++)
        {
            int sum = 0;
            for (int j = 0; j < regions.length; j++)
            {
                sum += regions[j][i];
            }
            System.out.println("Q" + rowIndex + ": " + currency.format(sum));
            rowIndex++;
        }

Answer 1

Shouldn't this rather look like ...

    rowIndex = 1;
    for (int j = 0; j < regions.length; j++) // here regions.length
    {
        int sum = 0;
        for (int i = 0; i < regions[j].length; i++) // here index j
        {
            sum += regions[j][i];
        }
        System.out.println("Q" + rowIndex + ": " + currency.format(sum));
        rowIndex++;
    }

Think you mixed up the indices ... Cheers!

Answer 2

You are messing up the indices of array. I Guess your code should be something like this:

   rowIndex = 1;
    for (int i = 0; i < regions.length; i++)
    {
        int sum = 0;
        for (int j = 0; j < regions[i].length; j++)
        {
            sum += regions[i][j];
        }
        System.out.println("Q" + rowIndex + ": " + currency.format(sum));
        rowIndex++;
    }