code: public static void setDividerLocation(
          final JSplitPane splitPane, final double location)
      {
          SwingUtilities.invokeLater(new Runnable()
          {
              @Override
              public void run()
              {
                  splitPane.setDividerLocation(location);
                  splitPane.validate();
              }
          });
      }
docs: Set the location of the the given split pane to the given
  value later on the EDT, and validate the split pane
  
  @param splitPane The split pane
  @param location The location