title: How to receive/forward Event from/to another Component in Java Swing
body: <p>i have a GUI which consists of a JTabbedPane.
  I have three different JPanels A B C which are added to the JTabbedPane.
  Every JPanel has a JComboBox and all of them are receiving their content from the same source (a txt-file).
  Only in JPanel A there is the possibility to add/remove/edit the JComboBox content in this txt-file.
  If i add/remove/edit the content of the JComboBox the other two JcomboBoxes in JPanel B and JPanel C have to be like refreshed to addopt the changes in the source.
  The changes are performed in a ActionListener event fired by a Jbutton.</p>
  
  <p>How can i forward these chnges in the txt-file which is the source of all JComboBxes to the other JPanels for the other two JComboxes to addopt the changes?</p>