Confused, whether java uses call by value or call by reference when an object reference is passed?

public class program1{

 public
            static void main(String args[]){

 java.util.Vector vc=new
            java.util.Vector();

 vc.add("111");


            vc.add("222");

 functioncall(vc);


            vc.add("333");

 System.out.println(vc);


            }


 public static void functioncall(java.util.Vector vc){
            

 vc=null; 


            }
}

The
output of above program is [111,222,333]. but, when I run the following program the
output is [333]. Confused when we pass an reference , how it works whether it is call by
value or call by reference? and
why

public class
            program1{

 public static void main(String
            args[]){

 java.util.Vector vc=new
            java.util.Vector();

 vc.add("111");

            vc.add("222");

 functioncall(vc);



            vc.add("333");

 System.out.println(vc);


            }

 public static void functioncall(java.util.Vector
            vc){

 vc.removeAllElements(); 



            }
}

class="post-text" itemprop="text">

class="normal">Answer

It passes
the value of the
reference.

To shamelessly steal an analogy I saw
posted on here a while ago, imagine that each identifier you use is a piece of paper
with an address written on it. The address points to a
house.

You can change the house (for example, by
adding objects to the vector or clearing it), but you're still holding the same piece of
paper, and the address still takes you to the same
house.

If you set the vector to null,
all you're doing is rubbing out the
address.

href="http://javadude.com/articles/passbyvalue.htm" rel="noreferrer">This
article explains it in much more detail.