JSplitPane Setting Resize Weight not Working

Question

I am trying to set the weight of the splitter to 0.9 yet it does not seem to work. What am I missing and what am i to do? I've checked this post, yet I could not neither understand nor solve the problem of mine. What I want basically is something like this though the split pane and the table is always %50,%50. So splitter.setResizeWeight( 0.9 ); is not working. Here's the code of the panel:

 public FlightPanel( final SomeOtherClass category, final SomeClass dar2 )
 {
   this.detailsPanel = new JPanel( new GridLayout( 0, 1 ) );
      this.sum = new JPanel( new GridLayout( 0, 1 ) );
      this.model =
            new FlightPanelTableModel(...);
  this.timeTable = new JTable( this.model );
  this.timeTable.setAutoResizeMode( JTable.AUTO_RESIZE_OFF );
  this.setLayout( new GridLayout( 0, 1 ) );


  this.treeView = new FlightPanelTreeView( dar2 );
  ToolTipManager.sharedInstance().registerComponent( this.treeView );

  this.detailsPanel.add( this.treeView );
  final JSplitPane splitter =
        new JSplitPane( JSplitPane.HORIZONTAL_SPLIT, new JScrollPane( this.timeTable ),
              new JScrollPane( this.detailsPanel ) );
  splitter.setResizeWeight( 0.9 );

  this.sum.add( splitter );
  this.add( this.sum );
 }

How could I solve it? Thanks in advance.