I am learning java and building one project to test basics.
I have one menu item FILE and then sub menu item like
1)Front
2)Admin
3)Booking
I have separate gui made in separate files but i want that they should be visible in one area , with click on submenus
I am using swing , JmenuBar . Also the other guis are using Jframe
Most applications should only ever have a single JFrame, which indeed is your requirement since you want the separate GUI to be visible in the same area.
Therefore your other GUI, should not extend JFrame but instead should extend JPanel. Then you can just use a CardLayout on your real GUI to swap the panels in/out depending on which panel is selected from your menu. All these basic are covered in the Swing tutorial. I guess you would start with the section on: