addition of two multidimensional array of different sizes

Question

I am learning Java for a week now and this program gives me an error in add method. I can't find out why?

int a[][]= {{211,21,32,34},{20,21}};
int b[][]={{31,42},{45,21}};

public static void add(int x[][], int y[][]){
    int ar=0,al=0,i=0;

    if(x.length>=y.length) {
        ar=x.length;
    } else {
        ar=y.length;
    }
    if(x[i].length>=y[i].length) {
        al=x[i].length;
    } else {
        al=y[i].length;
    }
    int s[][] = new int[ar][al];
    for(i=0; i<ar; i++) {
        for(int j=0; j<al; j++) {
            s[i][j]=x[i][j]+y[i][j];
        }
        for(i=0; i<ar; i++) {   
            for(int j=0; j<al; j++) {
                System.out.print(s[i][j]+" ");
            }
            System.out.print("\n");
        }
    }
}

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the variables `ar` and `al` are being initialized with the max(row of the arrays) and max(column of the array) now you tell me in this example the value of the al would be 4, how would you access fourth column of any row in second array, that why you are getting indexoutofbound.. — viveksinghggits, Jun 08 '16 at 14:30

score 0 · Accepted Answer · answered Jun 08 '16 at 14:33

The problem is in this code:

if(x.length>=y.length) //!!PROBLEM!!
{
    ar=x.length;
}
else{
    ar=y.length;
}
if(x[i].length>=y[i].length) //!!PROBLEM!!
{   al=x[i].length;

}
else{
    al=y[i].length;
}

You're taking the larger of the sizes between these two matrices, which means that whichever one is smaller will throw ArrayIndexOutOfBoundsExceptions whenever you try to index the larger rows/columns.

The logic should be flipped; take the minimum of these lengths:

if(x.length <= y.length) //FIXED
{
    ar=x.length;
}
else{
    ar=y.length;
}
if(x[i].length <= y[i].length) //FIXED
{
    al=x[i].length;
}
else{
    al=y[i].length;
}

addition of two multidimensional array of different sizes

1 Answers1