如何在Java中比较两个2D数组？

Question

I am a beginner trying to write a function in Java that returns true if two passed 2D arrays of int type are the same size in every dimension, and false otherwise. Requirements are that if both arrays are null you should return true . If one is null and the other is not you should return false .

Somehow getting an error for my code:

public static boolean arraySameSize(int[][] a, int[][] b) {
    if (a == null && b == null) {
        return true;
    }
    if (a == null || b == null) {
        return false;
    }
    if (a.length == b.length) {
        for (int i = 0; i < a.length; i++) {
            if (a[i].length == b[i].length) {
                return true;
            }
        }   
    }
    return false;
}

Any help would be appreciated!

Edit: Problem is "Runtime Error: null"

Answer 1

Your logic looks almost spot-on already. The only issue I see is in the logic handling the case where both arrays are not null and have the same first dimension. You should be returning false if any index does not have matching lengths:

public static boolean arraySameSize(int[][] a, int[][] b) {
    if (a == null && b == null) {
        return true;
    }
    if (a == null || b == null) {
        return false;
    }
    if (a.length != b.length) {
        return false;
    }

    // if the code reaches this point, it means that both arrays are not
    // null AND both have the same length in the first dimension
    for (int i=0; i < a.length; i++) {
        if (a[i] == null && b[i] == null) {
            continue;
        }
        if (a[i] == null || b[i] == null) {
            return false;
        }
        if (a[i].length != b[i].length) {
            return false;
        }
    }

    return true;
}

Follow the demo link below to see some of examples of this method working correctly.

Demo