Giữa kì

GiuaKi.java

import javax.swing.*;
import java.awt.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;

/**
 * untitled
 * Created by IntelliJ IDEA.
 * User: Trung Tin Nguyen
 * Date: 16/11/2021
 * Time: 8:16 pm
 */

class Ward {
    public int id;
    public String name;

    public String getName() {
        return name;
    }
}

class District {
    public int id;
    private String name;

    public Ward[] wards;

    public District(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }
}

public class GiuaKi extends JFrame {
    private static JPanel rootPanel = new JPanel();
    private ArrayList<District> districts = new ArrayList<>();

    GiuaKi(JPanel rootPanel) {
        getData();

        setTitle("District-Ward Chooser");
        setSize(800, 600);

        // set border layout
        rootPanel.setLayout(new BorderLayout());

        // create JPanel with flowlayout
        JPanel panel1 = new JPanel();
        panel1.setLayout(new FlowLayout());

        // create label and combo box
        JLabel label = new JLabel("Your district");
        JComboBox<String> comboBox = new JComboBox<>();

        // add items to combo box
        for (District district : districts) {
            comboBox.addItem(district.getName());
        }

        // add label and combo box to panel1
        panel1.add(label);
        panel1.add(comboBox);

        //add panel1 to top
        rootPanel.add(panel1, BorderLayout.NORTH);

        // create list select and add to panel2
        JPanel panel2 = new JPanel();
        panel2.setLayout(new FlowLayout());
        JList<String> list = new JList<>();

        JScrollPane scrollPane = new JScrollPane();
        scrollPane.setViewportView(list);
        list.setLayoutOrientation(JList.VERTICAL);

        // set list to sample
        String[] arr = {};
        // add wards to arr
        for (District district : districts) {
            if (district.getName().equals(comboBox.getSelectedItem())) {
                for (Ward ward : district.wards) {
                    arr[arr.length] = ward.getName();
                }
            }
        }

        // add arr to list
        list.setListData(arr);

        panel2.add(list);
        rootPanel.add(panel2, BorderLayout.CENTER);

        // create button and add to panel3
        JPanel panel3 = new JPanel();
        panel3.setLayout(new FlowLayout());
        JButton button = new JButton("Ok");
        JButton button2 = new JButton("Cancel");

        // add handle onclick for button to print out selected item and comboBox
        button.addActionListener(e -> {
            String selectedItem = (String) list.getSelectedValue();
            String comboBoxValue = (String) comboBox.getSelectedItem();

            // alert
            JOptionPane.showMessageDialog(null, selectedItem + "--" + comboBoxValue);
        });

        panel3.add(button);
        panel3.add(button2);

        rootPanel.add(panel3, BorderLayout.SOUTH);
    }

    public void getData() {
        Connection con = null;

        try {
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            con = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=hcmchooser;user=sa;password=password");
            if (con != null) {
                System.out.println("Connect successfully");
                String s = "select * from Districts";
                Statement st = con.createStatement();

                // load Districts into array
                ResultSet rs = st.executeQuery(s);
                while (rs.next()) {
                    District district = new District(rs.getInt("DistrictID"), rs.getString("DistrictName"));

                    // get ward from table Wards
                    String s1 = "select * from Wards where DistrictID = " + district.id;
                    Statement st1 = con.createStatement();
                    ResultSet rs1 = st1.executeQuery(s1);
                    int j = 0;
                    while (rs1.next()) {
                        Ward ward = new Ward();
                        ward.id = rs1.getInt("WardID");
                        ward.name = rs1.getString("WardName");
                        district.wards[j] = ward;
                        j++;
                    }

                    districts.add(district);
                }

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

    public static void main(String[] args) {
        GiuaKi frame = new GiuaKi(rootPanel);
        frame.setContentPane(frame.rootPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
        
    }
}