Summing column 2d matrix

public class SummingColumn8_1 {

    public static void main(String[] args) {
        // create a matrix
        int[][] matrix={
                {1,2,3},
                {4,5,6},
        };
        // outer loop controls the column number
        // inner loop advances present column to the next row
        for (int j=0; j<matrix[0].length; j++){
            int columnTotal=0;
            for (int i=0; i<matrix.length; i++){
                columnTotal+= matrix[i][j];
            }
            System.out.println("The total for column "+j+ " is "+ columnTotal);
        }

    }
}