A DESCRIPTION OF THE REGRESSION :
Previously one could use JDialog.EXIT_ON_CLOSE, this now throws an IllegalArgumentException.

IMO EXIT_ON_CLOSE is valid. We use a Modal JDialog for Login to our app. If the user select 'Cancel' we close the dialog and the VM exits. If they click OK we simply hide the dialog.

This is a regression especially since the JavaDocs don't mention the change!

REPRODUCIBLE TESTCASE OR STEPS TO REPRODUCE:
        JDialog d = new JDialog((JFrame) null, true);
        d.setDefaultCloseOperation(JDialog.EXIT_ON_CLOSE);


RELEASE LAST WORKED:
5.0 Update 6

RELEASE TEST FAILS:
mustang-beta

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
dlg.setDefaultCloseOperation(JDialog.EXIT_ON_CLOSE);
should process normally
ACTUAL -
dlg.setDefaultCloseOperation(JDialog.EXIT_ON_CLOSE);
throws an IllegalArgumentException