从动作执行者（组合框）中提取变量并在查询中使用它

Question

这是公共全局变量：

 public static String s;    

这是SQL查询 - ＆gt;规范它的工作，但没有条件WHERE

 String query = "SELECT * FROM `asistente` WHERE `sectie`="+s;
            System.out.println(s);
            Statement st;
            ResultSet rs;

  

S-＆GT;等于NULL

填充ComboBox - ＆gt;它的工作

public void fillComboBox() {

        try {
            String a = "jdbc:mysql://localhost/licenta";
            Connection connection = DriverManager.getConnection(a, "root", "");
            String query = "SELECT * FROM `sectii`";
            PreparedStatement pst = connection.prepareStatement(query);
            ResultSet rs = pst.executeQuery();
            while (rs.next()) {
                comboBoxSectie.addItem(rs.getString("sectie"));
                comboBoxFilterSectie.addItem(rs.getString("sectie"));

            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

这里我试图给出来自组合框的值

  public ModificareDB() {

comboBoxFilterSectie = new JComboBox();
        comboBoxFilterSectie.addActionListener(new ActionListener() {
            @Override 
            public void actionPerformed(ActionEvent e) {
            s=(String) comboBoxFilterSectie.getSelectedItem();
            System.out.println(s);
            }
        });

  

- ＆GT; s等于选定的值

如何在查询中使用从comboBox中选择的值？