you could use this sample for your JList :

    jt = new JTree(top); 
    int v = ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED; 
    int h = ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED; 
    JScrollPane jsp = new JScrollPane(jt, v, h); 
    panel.add(jsp, BorderLayout.CENTER);