How to count 2D int array in Java?

Question

Say for example I had the following:

    int[][] courses = {
            {1, 0},
            {2, 0},
            {3, 1},
            {3, 2},
    };

Now don't the first index represents x, and second index represents y? For example, courses[x][y], so courses[0][1], should print 2, but actually prints 0, why is that?

Because x=0 is the first index, so it gets the {1,0} , then y=1 is the second index and that gets you the 0. — applecrusher
– applecrusher, Commented Dec 11, 2016 at 6:59

Eran · Accepted Answer · 2016-12-11 07:05:04Z

3

A 2D array is actually an array whose elements are arrays.

The first index of the array is the index of the outer-most array.

Therefore courses[0] returns the inner array {1, 0} (the first element of the outer array) and courses[0][1] returns the second element of that array, which is 0.

courses[1][0] would return 2.

Now don't the first index represents x, and second index represents y

If you treat a 2D array as a matrix, and by x you mean column index and by y you mean row index, then actually it's the other way around - the first index is the row index (y) and the second index is the column index (x).

edited Dec 11, 2016 at 7:05

answered Dec 11, 2016 at 6:59

Eran

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Comments

andrew · Accepted Answer · 2016-12-11 07:05:17Z

0

courses[0,0]=1 courses[0,1]=0 - this is the first row

courses[1,0]=2 courses[1,1]=0 - this is the second row

courses[2,0]=3 courses[2,1]=1 - this is the third row

answered Dec 11, 2016 at 7:05

andrew

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