JOptionPane is slow - sometimes

Question

I am using JOptionPane to solicit input to my program.
I notice that if the program is not experiencing any user interaction for a period of time (several hours) then the JOptionPane window takes a long time to come up. Sometimes I have to wait about 2 seconds or more. Henceforth It comes up quickly until after I wait another long period of time. It is as though java is remembering something only immediately after using JOptionPane.
Can anybode tell me what is happening here? Why does it take longer to come up after being inactive for a long while, then subsequently comes up quickly until the next day? My application runs 24/7.
Here is my section of code from a KeyListener inner class:
if (k == e.VK_D)
String input = JOptionPane.showInputDialog("Enter name");
if(input != null) // test if cancel not pressed
if(input.toString().equals("")) {} // test if something entered
else
// action code in here
}

Answer 1

Thanks camikr.
I guess that sounds plausable except that the program is always running (collecting data) so why should JVM need to swap out?
Is there a way to have it stay in memory?