Creating an instance of Vector Class and adding an Element?

[Khoder Wassouf]

From the UCertified Mock Exam

The answer to this Following Question is: (4)

But when compiling (2),(3),(4) they Compiled and added an element!...............So why is Answer (4) only the right answer?.........And I need a Good Detailed Explanation Please

Which of the following will successfully create an instance of the Vector class and add an element?
1) Vector v=new Vector(99);
v[1]=99;

2) Vector v=new Vector();
v.addElement(99);

3) Vector v=new Vector();
v.add(99);

4 Vector v=new Vector(100);
v.addElement("99");

[Mohamed Sanaulla]

Please QuoteYourSources and you can have a look at the documentation for the java.util.Vector class.