Answer 1

It shouldn't be public static void main (String args [][])
But:
public static void main (String[] args)

Answer 2

The difference is the dimensions of the array.
For example if you try to get access to two dimensions array[][]:
String [][] args = new String [1][1]
args [0][0] = ...
But for one dimension array []:
String [] args = new String [1]
args [0] = ...