InternalFrameTitlePane implementation in Mac OSx is done in native level. There is no corresponding component in swing. But for all other OS there is one implementation of ‘BasicInternalFrameTitlePane’.

There are some APIs depends upon title pane. These all fails with NullPointerException:
getMinimizeButton()
getMaximizeButton()
getCloseButton()
getTitlePane()
getTitleOperator()
maximize()
demaximize()
iconify()
activate()