JFrame Won't Hide When New Applet Starts

I have a login window, which when sucessful will activate a new Applet/JFrame. The problem is that the login window remains in the background under the new JFrame. I want this to diappear. I want to either set the visibility to false, or close it.This is how the new window is started:

if(sucess.equals("flase")){

DBAccess dba = new DBAccess();
dba.setFname(fnameusr); //fnameusr
dba.setLname(lnameusr); //lnameusr
dba.main(null);

//LogIn.exit(0);
}else{
JOptionPane.showMessageDialog(null, "Your credentials were not entered correctly or you may not be authorised to access this system.");
System.exit(0);
}