There is a window,which contains a button n the code
is written in such a way that whenever the button is pressed , it
displays another window,but the problem is i want the child window
to be created only once evenif i press the button 10 times or
infinite number of times.

How is it possible , plz do mail me.

I have one more doubt , at wht points of time will a
person encounter NullPointerException.