Question

How to padarray in java that is add row and column to a existing array in front and back with a given number.

For example :-

let x =  1  2  3
         4  5  6
         7  8  9   

and now want to 2 rows and columns of zeros in this:

   x =  0 0 0 0 0 0 0 
        0 0 0 0 0 0 0
        0 0 1 2 3 0 0
        0 0 4 5 6 0 0
        0 0 7 8 9 0 0
        0 0 0 0 0 0 0
        0 0 0 0 0 0 0

So, i want to know that is there a existing method or way to do this in java like it is available in matlab using the predefined method called padarray(x,[r,c]).

Answer 1

You can never add rows or columns to 2 dimensional arrays at all. Arrays are fixed size. You could use a dynamic data structure such as List<List<Integer>>.

What you also can do is create a new array (that is bigger or smaller than your current one) using the Arrays.copyOf(int[] original, int newLength); method.

You array x is like:

  int[][] x = new int[][]{{1,2,3}, {4,5,6}, {7,8,9}};

There is no one-liner (I know of) to transform it to your desired format. You have to create a method that creates a new 2 dimensional array and place your values at the correct indexes.