I am working on a library management system program in Eclipse IDE. I am developing the GUIs but I am getting below nullPointerException error. I want to create a four JButton (Manage Material, Manage Patron, Load Data, Exit) button in my homepage and link with sub-menus.
Don't make your class a subclass of JFrame. A library IS‑NOT‑A frame; a library appliication HAS‑A frame.
Please learn how to break lines. your line 81 for example is too long to read. There is useful information in the old Sun style guide.