[10] RFR: 8182577: Crash when Tab key moves focus to a JCheckbox with a custom ButtonModel

[Prasanta Sadhukhan]

Hi All,

Please review a fix for an issue where a crash is reported when focus is 
moved with custom ButtonModel.
Issue was in LayoutFocusTraversalPolicy, the ButtonModel was wrongly 
typecasted to JToggleButton when the button model is DefaultButtonModel, 
resulting in ClassCastException.

Proposed fix is to cast to super class DefaultButtonModel and then check 
for JToggleButton member.

Bug: https://bugs.openjdk.java.net/browse/JDK-8182577
webrev: http://cr.openjdk.java.net/~psadhukhan/8182577/webrev.00/

Regards
Prasanta