JFrame Exit Button

Answer:
It is possible to disable the function of the close button on a JFrame, but it does not appear to be possile to remove it. The close button is placed by the native windowing system, and there do not seem to be any API hooks provided to tell the windowing system not to draw the button.

The easiest way to disable the close action on a JFrame is to call its setDefaultCloseOperation(). This method accepts an integer as a parameter representing the operation to perform. This value must be one of the constants defined in the WindowConstants interface. Using the value WindowConstans.DO_NOTHING_ON_CLOSE will do the trick. You will notice that JFrame implements the WindowConstants interface, so it is also possible to use JFrame.DO_NOTHING_ON_CLOSE, which may be clearer. Note, however, that JInternalFrame provides the ability to control the presence or absence of an exit button.