Java Error: IllegalArgumentException: adding a window to a container

Question

I keep receiving the error:

Exception in thread \"main\" java.lang.IllegalArgumentException: adding a window to a container
  at java.awt.Container.checkNotA         


        

Answer 1

EmployeeGUI extends from JFrame, but in your main method, you are creating a new JFrame and are trying to add an instance of EmployeeGUI to it.

Change EmployeeGUI so it extends from JPanel instead