Row-major vs Column-Major

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

​Row-major

​Column-major

​1 2 3 4 5 6 7 8

1 5 2 6 3 7 4 8

Project 8.1 - 8.1.6 Complete Chessboard

You could initialize every element either on its own line or in a loop:
int[][] arr = new int[8][8];
arr[0][0] = "Rook";
...
for (int i = ___; i < ___; i++) {
arr[?][?] = "Pawn";
}

You could initialize the whole 2D array at once:
int[][] arr = { {"Rook", "Knight", ...}, {...}, ... };

OR

Project 8.1 - 8.1.7 Tic Tac Toe Board

Initialize a tic-tac-toe board with dashes:
[
["-", "-", "-"],
["-", "-", "-"],
["-", "-", "-"]
]

For each row:
For each column:
arr[row][col] = "-";

Matrix operations