Arrays of Arrays

[Armstrong D]

can anybody explain this arrrays of arrays, i am getting confused with the nested for loops,
and what should i know in arrays of arrays as am preparing for the SCJP
class arr {
public static void main (String args[]) {
int twoD[][] = new int[2][3];
int i, j, k = 0;
for(i=0; i<2; i++)
for(j=0; j<3; j++) {
twoD[i][j] = k;
k++;
System.out.println(twoD[i][j]);
}
}
}
Thank you very much

[Valentin Crettaz]

In this case we have a bi-dimensional array. It is kind of like a matrix 2x3 (2 rows - 3 columns).
int twoD[][] = new int[2][3];
The nested for loops are needed in order to access each cell of the matrix.
for(int i=0;i<2;i++) will traverse the first and second row.
for(int j=0;j<3;j++) will traverse the first, the second and the third column.
Each cell is assigned k (incremented at each iteration). The content of the bi-dimensional array after its initialization is:

     |col0   col1   col2
-----+------------------
row0 |  0      1      2
row1 |  3      4      5