Generally, it would have been better to start a new thread rather than appending your question to a thread whose only relation to your topic is that it too concerns JTableHeader.
Without a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program[/url] that provides a framework for comments, it is hard to give you any specific advice.
That said, presumably you are using the values of the variables at some point to specify the column headers. This might be when you construct the table, or perhaps in the TableModel.
When the language is changed, you then change the values of those variables. Your table model then needs to do exactly what AbstractTableModel#fireTableStructureChanged does.