我的JList不能与另一个Jlist发生反应，换句话说，他们不会以某种方式连接，当我点击第二个jlist时它的值为null

Question

如何使3 JList相互连接？

private JList style = new JList(new String[] { "Monday", "Tuesday",
  "Wednesday", "Thursday", "Friday","Saturday","Sunday" });

private JList style2 = new JList(new String[] {"Lucy","bin"});

public void valueChanged（ListSelectionEvent evt）{         updateFont（）;

}


  public void updateFont() {

      String m = (String) style.getSelectedValue();
      System.out.println(m);

    if(style.getSelectedValue()== "Monday")
    {
        style2.setListData(new String[]{"Lucy"});
        String mn = (String) style2.getSelectedValue();
        System.out.println(mn);
        //style3.setListData(st.getTime(mn));

    }
    if(style.getSelectedValue()== "Tuesday")
    {
        style2.setListData(new String[]{"Lucy"});               
    }

    if(style.getSelectedValue()== "Wednesday")
    {
        style2.setListData(st.getMovieList());              
    }

    if(style.getSelectedValue()== "Thursday")
    {
        style2.setListData(st.getMovieList());              
    }

    if(style.getSelectedValue()== "Friday")
    {
        style2.setListData(st.getMovieList());              
    }

    if(style.getSelectedValue()== "Saturday")
    {
        style2.setListData(new String[] {"Lucy","bin"});                
    }
    if(style.getSelectedValue()== "Sunday")
    {
        style2.setListData(new String[] {"Lucy","bin"});                
    }

    repaint();