How to fix ArrayIndexOutOfBoundsException for a two dimensional array

Question

I am a beginner in Java programming and I just writing a simple program to return the sum of elements in the i-th column of the two-dimensional array.

But one of my test case gave me an ArrayIndexOutOfBoundsException error, which show as below:

The test case with issue occurred:

int[][] numbers3 = {{3}, {2, 4, 6}, {3, 6}, {3, 6, 9, 12}};
System.out.println(columnSum(3, numbers3));

This is the error message I got from this test case:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3
    at Array.columnSum(Array.java:12)
    at Array.start(Array.java:6)
    at ArrayApp.main(ArrayApp.java:7)

I don't know how to solve this problem...so could anyone please point out my mistake please ? Thank you !

Here's my code:

    public class Array {

    public void start() {
        int[][] numbers3 = {{3}, {2, 4, 6}, {3, 6}, {3, 6, 9, 12}};
        System.out.println(columnSum(3, numbers3));
    }

    private int columnSum(int i, int[][] nums) {
        int sum = 0;
        for(int row = 0; row < nums.length; row++){
            sum = sum + nums[row][i];
        }
        return sum;
    }
}

Here's some test cases I used which is working fine.

Test case 1:

int[][] nums = {{0, 1, 2, 3}, {2, 4, 6, 8}, {3, 6, 9, 12}};
System.out.println(columnSum(0, nums));

Test case 2:

int[][] nums2 = {{0, 1, 2, 3}, {2, 4, 6, 8}, {3, 6, 9, 12}};
System.out.println(columnSum(3, nums2));

Raceimaztion · Accepted Answer · 2015-07-29 04:43:25Z

6

Looking at your array

int[][] numbers3 = {{3}, {2, 4, 6}, {3, 6}, {3, 6, 9, 12}};

numbers3[0] is only {3}, which is an array size of 1. Thus, calling numbers[3][x] where x is anything other than 0. will throw an error since it only has that element.

You have two options:

Only use arrays with the same number of elements.

int[][] numbers3 = {{3,1,3}, {2, 4, 6}, {3, 6,5}, {3, 6, 9}};

Add a check and pass in 0 instead

if(nums[row].length > i)
    sum = sum + nums[row][i];

This way, it never attempts to check the invalid index of nums[row].

edited Jul 29, 2015 at 4:43

Raceimaztion

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answered Jul 29, 2015 at 4:04

Arhowk

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Comments

Ryan · Accepted Answer · 2015-07-29 04:04:13Z

1

It's happening because your column lengths are different in that example so the third column doesn't exist.

private static int columnSum(int i, int[][] nums) {
    int sum = 0;
    for(int row = 0; row < nums.length; row++){
        if (i < nums[row].length) {
            sum = sum + nums[row][i];
        }
    }
    return sum;
}

answered Jul 29, 2015 at 4:04

Ryan

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