Using the variable `length`, it is possible to obtain the number of rows
and of columns of a matrix. Let `m` be a reference to a matrix (i.e.,
an array of arrays). Then

`m.length`denotes the**number of rows**of the matrix`m``m[i].length`denotes the**number of columns**of row`i`of matrix`m`*Note:*If all rows have the same number of columns (as in the previous example), we can simply use`m[0].length`.

*Example:*

double[][] v; v = new double[15][20]; System.out.println(v.length); // prints out 15 System.out.println(v[0].length); // prints out 20