Draw a 2D array of v?

Question

This is the code my teacher gave us. We have to draw a 2D array of v.

int[][] b = { {1, 2, 3, 4}, 
              {1, 0, 1, 0}, 
              {0, 1, 0, 1}, 
              {1, 0, 1, 0} };

int[][] v = new int[2][4];
int row = 0;
for (int i = 0; i < b.length; i++)
{
    for (int j = 0; j < b[i].length; j++)
        v[row][j] += b[i][j];
    row = (row + 1) % 2;
}

First of all I created a 2D array with 2 rows and then 4 columns for each row. I don´t really understand these 2 lines:

v[row][j] += b[i][j];
row = (row + 1) % 2; 

This is the answer . Why is it?

Answer 1

v[row][j] += b[i][j]; stands for v[row][j] =v[row][j] + b[i][j]; row = (row + 1) % 2; means divide row+1 by 2 and assign the remainder to row .