Error FormUser

package Forms;

import Tools.KoneksiDB;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.JOptionPane;
import javax.swing.table.DefaultTableModel;

public class IfrUser extends javax.swing.JInternalFrame {

    KoneksiDB getCon = new KoneksiDB();
    Connection _con;
    String sqlselect, sqlinsert, sqldelete;
    private DefaultTableModel dtmUser;
    String vid_user, vnama_user, vpass, vlev_user;

    public IfrUser() {
        initComponents();
        formTengah();
        clearForm();
        disableForm();
        setTabel();
        showDataTabel();
    }

    private void clearForm() {
        cmbLevUser.setSelectedIndex(0);
        txtIdUser.setText("");
        txtNamaUser.setText("");
        btnSimpan.setText("Simpan");
    }

    private void disableForm() {
        cmbLevUser.setEnabled(false);
        txtIdUser.setEnabled(false);
        txtNamaUser.setEnabled(false);
        btnSimpan.setEnabled(false);
        btnHapus.setEnabled(false);
    }

    private void enableForm() {
        cmbLevUser.setEnabled(true);
        txtIdUser.setEnabled(true);
        txtNamaUser.setEnabled(true);
        btnSimpan.setEnabled(true);
        btnHapus.setEnabled(true);
    }

    private void setTabel() {
        String[] kolom1 = {"ID. User", "Nama User", "Password", "Level User"};
        dtmUser = new DefaultTableModel(null, kolom1) {
          Class[] types = new Class[] {
              java.lang.String.class,
              java.lang.String.class,
              java.lang.String.class,
              java.lang.String.class
          };
          public Class getColumnClass(int columnIndex) {
              return types[columnIndex];
          }

          //agar tabel tidak bisa diedit
          public boolean isCellEditable(int row, int col) {
              int cola = dtmUser.getColumnCount();
              return (col < cola) ? false : true;
          }
        };
        tblDataUser.setModel(dtmUser);
        tblDataUser.getColumnModel().getColumn(0).setPreferredWidth(75);
        tblDataUser.getColumnModel().getColumn(1).setPreferredWidth(200);
        tblDataUser.getColumnModel().getColumn(2).setPreferredWidth(150);
        tblDataUser.getColumnModel().getColumn(3).setPreferredWidth(150);
    }

    private void clearTabel() {
        int row = dtmUser.getRowCount();
        for(int i = 0; i < row; i++) dtmUser.removeRow(0);
    }

    private void showDataTabel() {
        try {
            _con = null;
            _con = getCon.getConnection();
            sqlselect = "select * from tbuser order by id_user asc";
            Statement stat = _con.createStatement();
            ResultSet rs = stat.executeQuery(sqlselect);
            while(rs.next()) {
                vid_user = rs.getString(1);
                vnama_user = rs.getString(2);
                vpass = rs.getString(3);
                vlev_user = rs.getString(4);
                Object[] data = {vid_user, vnama_user, vpass, vlev_user};
                dtmUser.addRow(data);
            }
            lbRecord.setText("Record: " + tblDataUser.getRowCount());
        }catch(SQLException se) {
            JOptionPane.showMessageDialog(this, "Error method showDataTabel() : " +se);
        }
    }

    private void aksiSimpan() {
        vid_user = txtIdUser.getText();
        vnama_user = txtNamaUser.getText();
        vlev_user = cmbLevUser.getSelectedItem().toString();
        if(btnSimpan.getText().equals("Simpan")) {
            sqlinsert = "insert into tbuser values ('"+vid_user+"', '"+vnama_user+"', " + " '123456', '"+vlev_user+"')";
        }else {
            sqlinsert = "update tbuser set nama_user='"+vnama_user+"', lev_user = '"+vlev_user+"' " + " where id_user='"+vid_user+"'";
        }
        try {
            _con = null;
            _con = getCon.getConnection();
            Statement stat = _con.createStatement();
            stat.executeQuery(sqlinsert);
            JOptionPane.showMessageDialog(this, "Data berhasil disimpan", "Informasi", JOptionPane.INFORMATION_MESSAGE);
            showDataTabel(); clearForm(); disableForm();
        }catch(SQLException se) {
            JOptionPane.showMessageDialog(this, "Errot method aksiSimpan()" +se);
        }
    }

    private void aksiHapus() {
        int jawab = JOptionPane.showConfirmDialog(this, "Anda yakin ingin menghapus data? ID. User: " +vid_user, "Konfirmasi", JOptionPane.YES_NO_OPTION);
        if(jawab == JOptionPane.YES_OPTION) {
            try{
                _con = null;
                _con = getCon.getConnection();
                sqldelete = "delete from tbuser where id_user='"+vid_user+"'";
                Statement stat = _con.createStatement();
                stat.executeQuery(sqldelete);
                JOptionPane.showMessageDialog(this, "Data berhasil dihapus", "Informasi", JOptionPane.INFORMATION_MESSAGE);
                clearForm(); disableForm(); showDataTabel();
            }catch(SQLException se) {
                JOptionPane.showMessageDialog(this, "Error method aksiHapus()" +se);
            }
        }
    }

    private void formTengah() {
        Dimension screensize = Toolkit.getDefaultToolkit().getScreenSize();
        Dimension framesize = this.getSize();
        if(framesize.height < screensize.height) framesize.height = screensize.height;
        if(framesize.width > screensize.width) framesize.width = screensize.width;
        this.setLocation((screensize.width - framesize.width) / 2, (screensize.height - framesize.height) / 2);
    }

    private void btnTambahActionPerformed(java.awt.event.ActionEvent evt) {
        enableForm(); clearForm(); cmbLevUser.requestFocus(true);
    }

    private void btnSimpanActionPerformed(java.awt.event.ActionEvent evt) {
        if(txtIdUser.getText().equals(""))
            JOptionPane.showMessageDialog(this, "ID. User belum terisi", "Informasi", JOptionPane.INFORMATION_MESSAGE);
        else if(txtNamaUser.getText().equals(""))
            JOptionPane.showMessageDialog(this, "Nama User belum terisi", "Informasi", JOptionPane.INFORMATION_MESSAGE);
        else if(cmbLevUser.getSelectedIndex() <= 0)
            JOptionPane.showMessageDialog(this, "Level User belum terisi", "Informasi", JOptionPane.INFORMATION_MESSAGE);
        else aksiSimpan();
    }

    private void btnHapusActionPerformed(java.awt.event.ActionEvent evt) {
       if(txtIdUser.getText().equals(""))
            JOptionPane.showMessageDialog(this, "Anda belum memilih data yang akan dihapus", "Informasi", JOptionPane.INFORMATION_MESSAGE);
       else aksiHapus();
    }

    private void tblDataUserMouseClicked(java.awt.event.MouseEvent evt) {
        if(evt.getClickCount() == 2) {
            int brs = tblDataUser.getSelectedRow();
            vid_user = tblDataUser.getValueAt(brs, 0).toString();
            vnama_user = tblDataUser.getValueAt(brs, 1).toString();
            vlev_user = tblDataUser.getValueAt(brs, 3).toString();
            txtIdUser.setText(vid_user);
            txtNamaUser.setText(vnama_user);
            cmbLevUser.setSelectedItem(vlev_user);
            enableForm();
            txtIdUser.setEnabled(false);
            btnHapus.setEnabled(true);
            btnSimpan.setText("Ubah");
        }
    }

    private javax.swing.JButton btnHapus;
    private javax.swing.JButton btnSimpan;
    private javax.swing.JButton btnTambah;
    private javax.swing.JComboBox<String> cmbLevUser;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JLabel lbRecord;
    private javax.swing.JTable tblDataUser;
    private javax.swing.JTextField txtIdUser;
    private javax.swing.JTextField txtNamaUser;
    // End of variables declaration
}