How to understand Loops and Array in java

Question

I am quite confused in array loops that do have nested ones to print the Two Dimensional array. /it contains a loop without curly braces and second one has just opposite way of representing the braces for loops ...

Since i am learning I have just typed the code and got output.

public class TwoDimensional {
    private int i, j, k = 0;
    int[][] twod = new int[4][5];

    public void DoubleT() {
        for (i = 0; i < 4; i++)
            for (j = 0; j < 5; j++) {
                twod[i][j] = k;
                k++;

            }
        for (i = 0; i < 4; i++) {
            for (j = 0; j < 5; j++)
                System.out.print(twod[i][j] + " ");
            System.out.println();
        }
    }
}

The result it generates is 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19