Closing java dialog

Question

Dear all
Am facing problem closing my forms am developing multiple form soft phone
For calling the next page am using this code :
private aboutBox aboutBox;
JFrame mainFrame = MyownprojectApp.getApplication().getMainFrame();
aboutBox = new MyownprojectAboutBox(mainFrame);
aboutBox.setLocationRelativeTo(mainFrame);
aboutBox it's the screen it's working fine for the first time but if i close this dialog using
Windows red X button or using dispose code it close but if i call it again without shutdown
My application it show the window but as before i close it it's like hide and show without
Shutting it or starting it and operate the code with it i have to shut down the application then
Start it again ,
note : i create my soft phone using net beans and my main page type = jPanal and ather pages jDialog
i don't know where is the wrong maybe i create jDialog is that correct or what if it's not what is the
what is the correct way to create multiple form using net beans and how i can call it and i will post code
for my close command :
stopMedia();
if (aboutBox == null) {
JFrame mainFrame = MyownprojectApp.getApplication().getMainFrame();
mainPage main = new mainPage(mainFrame);
main.setVisible(false);
setVisible(false);
main.removeAll();
main.dispose();
aboutBox = new progress(mainFrame);
aboutBox.setLocationRelativeTo(mainFrame);
aboutBox.setEnabled(true);
MyownprojectApp.getApplication().show(aboutBox);
Or I use this one but the same
SetDefaultCloseOperation (javax.swing.WindowConstants.EXIT_ON_CLOSE);
and thanks for all

Answer 1

What i need is like am starting new application if i press start command it will start the dialog from zero If i close this dialog and press start command it will start the dialog from zero but what am getting is Like hide and show if i press close command the dialog will become hide if i press start it will show Dialog only not start it from beginning that the problem.
Also my code does not check if it's null so what i can do now and thanks.