Copying array elements within multidimensional arrays in Java

Question

So I'm having some trouble with this in java. This method is supposed to take in two String arrays which are multidimensional. This method is supposed to return a a copy String array. Now these two arrays that are being sent to the copy method are going to have randomly generated lengths within the arrays. I am trying to see if array2 is smaller than array and if it is then array will be assigned the length of array2 and I want to copy elements from array into array2. If it is the opposite with array2 being bigger than array then I would like to copy the elements from array into array2 and then the REMAINING spots in array2 will get filled with an *. Now the issue is I keep getting runtime errors with out of bounds for the index. It is specifically the lines that I have indicated with double asterisks below(within for loops) that are giving me issues. What could I do to solve the issue.

    public static String[][][] copy(String[][][] array, String[][][] array2){
    if(array2.length < array.length){
        array = new String[array2.length][array2.length][array2.length];
        for(int i = 0; i < array2.length; i++){
            for(int j = 0; j < array2[i].length; j++){
                for(int k = 0; k < array2[i][j].length; k++){
                    **array2[i][j][k] = array[i][j][k];**
                }
            }
        }
        return array2; 
    }
    if(array2.length > array.length){

        for(int i = 0; i < array.length; i++){
            for(int j = 0; j < array[i].length; j++){
                for(int k = 0; k < array[i][j].length; k++){
                    **array2[i][j][k] = array[i][j][k];**
                }
            }
        }
        for(int i = array.length - 1; i < array2.length; i++){
            for(int j = array[i].length - 1; j < array2.length; j++){
                for(int k = array[i][j].length - 1; k < array2.length; k++){
                    array2[i][j][k] = "*";
                }
            }
        }
        return array2;
    }
    return array;
}

could someone else provide any input?

user181421
– user181421

2016-05-02 23:53:19 +00:00
Commented May 2, 2016 at 23:53 — user181421
– user181421, Commented May 2, 2016 at 23:53

Vampire · Accepted Answer · 2016-05-02 22:46:20Z

1

You assume that each dimension of the array is of equal size.
But you cannot even assume that two sibling arrays are of equal size.
What I mean is, that array = new String[array2.length][array2.length][array2.length]; is nonsense and at least in two ways.
You probably want to have array2 = new String[array.length][][], because if you reassign array you will just copy nulls around. And for the lengths of the other dimensions you have to do the same comparisons and resizings, especially if you did not reassign the array2. If you did, then you have to create the sub-level arrays afresh anyway.

answered May 2, 2016 at 22:46

Vampire

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5 Comments

Vampire Over a year ago

That's a start, but by far not the fix of your code. Start a debugger and try understanding your code. And maybe read a book about Java and its arrays. ;-)

user181421 Over a year ago

for the first if statement, only array elements up to the length of array2 should be copied so I'm not so sure if array2 = new String[array.length][][] would work.

Vampire Over a year ago

Probably not, but if you copy from array to array2, array2 is smaller than array and you should crop at array2.length, then it makes absolutely no sense to assign array or array2 with a new value at all.

user181421 Over a year ago

Ya I just tried both ways and I'm still getting runtime errors for that specific line.

Vampire Over a year ago

As I told you, your code logic is totally screwed. You have to completely rethink or debug your logic. I just explained you your question, which was why you get AIOOBEs.

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