To begin with, Vectors are different from arrays.

   new Object[0] -- creates an array which can never have any elements
  new Object[100] -- creates an array with 100 elements, all of which are
null to begin with

   new Vector(0) -- create a Vector with no space allocated for elements,
but to which as many elements can be added as you like.  It starts with
none.
   new Vector(100) -- create a Vector with space allocated for 100
elements, but to which as many elements can be added as you like.  It starts
with none.

In either case, if you want to add elements to your new Vector, you can use
the add() method (or create a ListIterator on the Vector and use its add()
method.)

Of course it does; the Vector has no elements.

Of course it does; the Vector has no elements.

If you haven't instantiated it, it should be null.
It is only natural.
Try this:
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import java.util.*;

public class VecVec{

 public static void main(String[] args){
   Vector<Vector<Integer>> vvi;
   Vector<Integer> elem = null;

   vvi = new Vector<Vector<Integer>>();
   for (int i = 0; i < 100; ++i){
     vvi.add(new Vector<Integer>());
   }

   Enumeration<Vector<Integer>> it = vvi.elements();
   if (it.hasMoreElements()){
     elem = (Vector<Integer>)it.nextElement();
   }
   System.out.println(elem != null);

   elem = null;
   ListIterator<Vector<Integer>> lit = vvi.listIterator();
   if (lit.hasNext()){
     elem = (Vector<Integer>)lit.next();
   }
   System.out.println(elem != null);
 }