sheeshh

private void koneksi(){
  try {
    String url = "jdbc:mysql://localhost/coba";
    String user = "root";
    String pass = "";
    DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
    conn = (Connection) DriverManager.getConnection(url, user, pass);
    pre = conn.prepareStatement("select * from data");
    res = pre.executeQuery();
  } catch(Exception e) {
    JOptionPane.showMessageDialog(null, e);
    System.err.println("koneksi gagal + e.getMessage());
    System.exit(0);
  }
}





private void display(){
  DefaultTableModel model = new DefaultTableModel();
  model.addColumn("NISN");
  model.addColumn("Nama");
  model.addColumn("Jenis Kelamin");
  model.addColumn("Kelas");
  model.addColumn("Jurusan");

  try {
    pre = conn.prepareStatement("select * from data");
    res = pre.executeQuery();

    while (res.next()) {
      model.addRow(new Object[]{
      res.getString("nisn"),
      res.getString("nama"),
      res.getString("jk"),
      res.getString("kelas"),
      res.getString("jurusan")
      });
    }
    tabel.setModel(model);
  } catch(Exception e) {
      JOptionPane.showMessageDialog(null, e);
      System.exit(0);
  }
}





private void save(){
  String nisn = txtNISN.getText();
  String nama = txtNama.getText();
  String jk = "";
  if (rbl.isSelected()) {
    jk = "Laki-laki";
  } else if (rb2.isSelected()) {
    jk = "Perempuan";
  }
  String kelas cmbkelas.getSelectedItem().toString();
  String jurusan = "";
  if (cb1.isSelected()) {
    jurusan = "TРВО";
  }else if (cb2.isSelected()) {
    jurusan = "TSM";
  } else if (cb3.isSelected()) {
    jurusan = "RPL";
  } else if (cb4.isSelected()) {
    jurusan = "AK";
  }
}




private void update(){
  int selectedRow = tabel.getSelectedRow();
  System.out.println(selectedRow);
  if (selectedRow == -1){
    JOptionPane.showMessageDialog(null, "Pilih tabel yang akan diperbarui!");
  } else{
    String nisn = txtNISN.getText();
    String nama = txtNama.getText();
    String jk = "";
    if (rbl.isSelected()) {
      jk = "Laki-laki";
    } else if (rb2.isSelected()) {
      jk = "Perempuan";
    }
    String kelas = cmbkelas.getSelectedItem().toString();
    String jurusan = "";
    if (cbl.isSelected()) {
      jurusan = "TРВО";
    } else if (cb2.isSelected()) {
      jurusan = "TSM";
    } else if (cb3.isSelected()) {
      jurusan = "RPL";
    } else if (cb4.isSelected()) {
      jurusan = "AK";
    }
    try {
      sql = "update data set nama = '"+nama+"', jk = '"+jk+"', kelas = '"+kelas+"', jurusan = '"+jurusan+"' where nisn = '"+nisn+"'"";
      pre conn.prepareStatement(sql);
      pre.executeUpdate();
      display();
      JOptionPane.showMessageDialog(null, "Data berhasil ditambahkan!");
    } catch (Exception e){
      JOptionPane.showMessageDialog(null, e.getMessage());
    }
  }
}




private void delete(){
  int selectedRow = tabel.getSelectedRow();
  if (selectedRow == -1) {
    JOptionPane.showMessageDialog(null, "Pilih tabel yang akan dihapus!");
  }else{
    try {
      sql = "delete from data where nisn = '"+nisn+"'";
      pre conn.prepareStatement(sql);
      pre.executeUpdate();
      display();
      JOptionPane.showMessageDialog(null, "Data berhasil dihapus!");
    } catch(Exception e) {
      JOptionPane.showMessageDialog(null, e.getMessage());
    }
  }
}






private void tblClicked(){
  int selectedRow = tabel.getSelectedRow();
  if (selectedRow != -1)) {
    String nisn = tabel.getValueAt(selectedRow, 0).toString();
    String nama = tabel.getValueAt(selectedRow, 1).toString();
    String jk = tabel.getValueAt(selectedRow, 2).toString();
    String kelas = tabel.getValueAt(selectedRow, 3).toString();
    String jurusan = tabel.getValueAt(selectedRow, 4).toString();
    txtNISN.setText(nisn);
    txtNama.setText(nama);

    switch(jk){
      case "Laki-laki":
        rbl.setSelected(true);
        break;
      case "Perempuan":
        rb2.setSelected(true);
        break;
      default:
        throw new AssertionError();
    }
    cmbkelas.setSelectedItem(kelas);
    switch(jurusan){
      case "TPBO":
        cbl.setSelected(true);
        break;
      case "TSM":
        cb2.setSelected(true);
        break;
      case "RPL":
        cb3.setSelected(true);
        break;
      case "AK":
        cb4.setSelected(true);
        break;
      default:
        throw new AssertionError();
    }
  }
}