program error when enter data in array and display null

Question

i have done some correction by referring in here, but still haven quite satisfy of my program and it still not complete.
Problem 1 = my displayReg() comes out \"nullnullnull

Answer 1

Register[] a = new Register[i]; - creates an array with 0 items.

a[i].Reg(); - access to the position 0 of an array that got no items at all.

Here is a tutorial