FULL PRODUCT VERSION :
java version "1.7.0_02"
Java(TM) SE Runtime Environment (build 1.7.0_02-b13)
Java HotSpot(TM) Client VM (build 22.0-b10, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows Vista (32 bit)

A DESCRIPTION OF THE PROBLEM :
JOptionPane behavior has change in JDK 1.7,
and can break existing applications (typically illegal cast exception),
because for some scenarios, JOptionPane.getValue() now returns JOptionPane.UNINITIALIZED_VALUE while it was returning Integer(0) before.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the following program.
Enter some text in the the dialog and *press enter key*.
(If you click a button, this bug is not triggered.)



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
"Resut => 0"
(like JRE 1.6)

ACTUAL -
"Resut => uninitializedValue"


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
        JOptionPane pane = new JOptionPane("Enter value", JOptionPane.QUESTION_MESSAGE,
                JOptionPane.OK_CANCEL_OPTION, null,null, null);
        pane.setWantsInput(true);
        JDialog dialog = pane.createDialog(null, "My Dialog");
        dialog.setVisible(true);
        Object result = pane.getValue();
        System.out.println("Resut => " + result);
        dialog.dispose();
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
In client code, check if result is JOptionPane.UNINITIALIZED_VALUE and use 0 instead.