problem with Static Vector

[Pratik Khetia]

I am designing a chat server and to keep track of the user that are logged on. I am using a class which has static method and a static Vector. But when I pass the argument from other program this static Vector gives an error...
"java.lang.NullPointer"
or if I initialise the vector then I lose the traack of the users as everytime it stores in a new instance of the Vector.
So if anyone has any idea...I would look forward to get some help
thanks
Pratik Khetia

[Aleksey Matiychenko]

Well, you have to initialize the vector once. So how about putting something like this before accessing a vector
if (static_vector == null)
static_vector = new Vector();
... continue using vector