Question

How to prevent to close Java swing Application, when user clicks on close button?

Answer 1

frame.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE); on your main frame should prevent that.

The setDefaultCloseOperation(int) method allows you to choose what to do when the user closes the JFrame:

• DO_NOTHING_ON_CLOSE (defined in WindowConstants): Don’t do anything;
  require the program to handle the
  operation in the windowClosing method
  of a registered WindowListener object.

• HIDE_ON_CLOSE (defined in WindowConstants): Automatically hide
  the frame after invoking any
  registered WindowListener objects.

• DISPOSE_ON_CLOSE (defined in WindowConstants): Automatically hide
  and dispose the frame after invoking
  any registered WindowListener objects.

• EXIT_ON_CLOSE (defined in JFrame): Exit the application using the System
  exit method. Use this only in
  applications.