Question

I am trying to initialize a 2D array, in which the type of each element is char.
So far, I can only initialize this array in the follow way.

public class ticTacToe 
{
private char[][] table;

public ticTacToe()
{
    table[0][0] = '1';
    table[0][1] = '2';
    table[0][2] = '3';
    table[1][0] = '4';
    table[1][1] = '5';
    table[1][2] = '6';
    table[2][0] = '7';
    table[2][1] = '8';
    table[2][2] = '9';
}
}

I think if the array is 10*10, it is the trivial way.
Is there any efficient way to do that?

Answer 1

How about something like this:

for (int row = 0; row < 3; row ++)
    for (int col = 0; col < 3; col++)
        table[row][col] = (char) ('1' + row * 3 + col);

The following complete Java program:

class Test {
    public static void main(String[] args) {
        char[][] table = new char[3][3];
        for (int row = 0; row < 3; row ++)
            for (int col = 0; col < 3; col++)
                table[row][col] = (char) ('1' + row * 3 + col);

        for (int row = 0; row < 3; row ++)
            for (int col = 0; col < 3; col++)
                System.out.println (table[row][col]);
    }
}

outputs:

1
2
3
4
5
6
7
8
9

This works because the digits in Unicode are consecutive starting at \u0030 (which is what you get from '0').

The expression '1' + row * 3 + col (where you vary row and col between 0 and 2 inclusive) simply gives you a character from 1 to 9.

Obviously, this won’t give you the character 10 (since that’s two characters) if you go further but it works just fine for the 3×3 case. You would have to change the method of generating the array contents at that point such as with something like:

String[][] table = new String[5][5];
for (int row = 0; row < 5; row ++)
    for (int col = 0; col < 5; col++)
        table[row][col] = String.format("%d", row * 5 + col + 1);