kelas koneksi
package Class;

import java.sql.*;

public class Koneksi {

   protected final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
   protected final String DB_URL = "jdbc:mysql://localhost/dbakademik";


   protected final String USER = "root";
   protected final String PASS = "";

   protected Connection conn = null;
   protected Statement stmt = null;

   //konsturtor

   public Koneksi(){

   }
   public void openConn(){

       try{
           Class.forName("com.mysql.jdbc.Driver");
           conn = DriverManager.getConnection(DB_URL,USER,PASS);

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

   }
   public void closeConn(){

       try{
         if(conn!=null)
            conn.close();

      }catch(SQLException se){
         se.printStackTrace();
   }
}
}


---------------------------------------------------------------------------------------------

frame utama

public class FramUtama extends javax.swing.JFrame {
    public String gender;
   public FramUtama() {
        initComponents();

        Mahasiswa mhs = new Mahasiswa();
        DefaultTableModel dtm = mhs.tampil();
        jTable1.setModel(dtm);

    }

        String jk;
        String jurusan;
        String waktu;


    private void bSimpanActionPerformed(java.awt.event.ActionEvent evt) {
        Mahasiswa m = new Mahasiswa();

        String npm = (txtNpm.getText().toString());
        String nama = (txtNama.getText().toString());
        int usia = Integer.parseInt(txtUsia.getText().toString());

        if(rLaki.isSelected() || rPerempuan.isSelected()){
            if (rLaki.isSelected()){
                jk = "laki-laki";
            }
            else jk = "perempuan";
        }


        String jurusan = cbJurusan.getSelectedItem().toString();

        if(rPagi.isSelected() || rMalam.isSelected()){
            if(rPagi.isSelected()){
                waktu = "Pagi";
            }
            else waktu = "Malam";
        }
        m.setNPM(npm);
        m.setNama(nama);
        m.setUsia(usia);
        m.setJK(jk);
        m.setJurusan(jurusan);
        m.setWaktu(waktu);
        m.simpan(m);

        DefaultTableModel dtm = m.tampil();
        jTable1.setModel(dtm);



    }

    private void bUbahActionPerformed(java.awt.event.ActionEvent evt) {


        Mahasiswa m = new Mahasiswa();

        String npm = (txtNpm.getText().toString());
        String nama = (txtNama.getText().toString());
        int usia = Integer.parseInt(txtUsia.getText().toString());

        if(rLaki.isSelected() || rPerempuan.isSelected()){
            if (rLaki.isSelected()){
                jk = "laki-laki";
            }
            else jk = "perempuan";
        }

        String jurusan = cbJurusan.getSelectedItem().toString();

        if(rPagi.isSelected() || rMalam.isSelected()){
            if(rPagi.isSelected()){
                waktu = "Pagi";
            }
            else waktu = "Malam";
        }

        m.setNPM(npm);
        m.setNama(nama);
        m.setUsia(usia);
        m.setJK(jk);
        m.setJurusan(jurusan);
        m.setWaktu(waktu);
        m.ubah(m);
        DefaultTableModel dtm = m.tampil();
        jTable1.setModel(dtm);
    }

    private void bhapusActionPerformed(java.awt.event.ActionEvent evt) {
        Mahasiswa m = new Mahasiswa();

        String npm = (txtNpm.getText().toString());

        m.setNPM(npm);

        m.hapus(m);
        DefaultTableModel dtm = m.tampil();
        jTable1.setModel(dtm);
    }

    private void rLakiActionPerformed(java.awt.event.ActionEvent evt) {
          gender ="laki";  // TODO add your handling code here:
    }

    private void rPerempuanActionPerformed(java.awt.event.ActionEvent evt) {
          gender = "perempuan";
    }

---------------------------------------------------------------------------------------------------------------\
kelas mahasiswa\


//nama file mahasiswa.java
//lokasi : src/class/mahasiswa.java
package Class;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import javax.swing.table.DefaultTableModel;

public class Mahasiswa extends Koneksi{
    protected String npm;
    protected String nama;
    protected int usia;
    protected String jk;
    protected String jurusan;
    protected String waktu;
    protected String gender;
    private String sql;






    public void setNPM(String npm){
        this.npm = npm;
    }
    public void setNama(String nama){
        this.nama = nama;
    }
    public void setUsia(int usia){
        this.usia = usia;
    }
    public void setJK(String jk){
        this.jk = jk;
    }
    public void setJurusan(String jurusan){
        this.jurusan = jurusan;
    }
    public void setWaktu(String waktu){
        this.waktu = waktu;
    }

    public void simpan(Mahasiswa m){

        try{
            this.openConn();
            this.stmt = this.conn.createStatement();
            sql = "insert into tblmahasiswa values " +
                    "('" + m.npm + "','" + m.nama + "','" + m.usia + "'" +
                    ",'" + m.jk + "','" + m.jurusan + "','" + m.waktu + "')";
            stmt.executeUpdate(sql);

            this.closeConn();

        }
        catch(SQLException se){
            se.printStackTrace();
        }

    }

    public void ubah(Mahasiswa m){

        try{
         this.openConn();
            this.stmt = this.conn.createStatement();
            sql = "UPDATE tblmahasiswa "
                     + "SET nama = '" + m.nama + "', usia = '" + m.usia + "',"
                    + "`jenis kelamin` = '" +m.jk+ "', jurusan = '" +m.jurusan+ "', `waktu kuliah`   = '" +m.waktu+ "'"
                     + "WHERE npm = '" + m.npm + "'";
            stmt.executeUpdate(sql);

            this.closeConn();
        }
        catch(SQLException se){
            se.printStackTrace();
        }

    }
    public void hapus(Mahasiswa m){
        try{
         this.openConn();
            this.stmt = this.conn.createStatement();
            sql = "DELETE FROM tblmahasiswa " + "WHERE npm = '" + m.npm + "'";
            stmt.executeUpdate(sql);

            this.closeConn();
        }
        catch(SQLException se){
            se.printStackTrace();
        }
    }

    public DefaultTableModel tampil(){

        try{
            this.openConn();
            this.stmt = this.conn.createStatement();
            sql = "SELECT *FROM tblmahasiswa";
            ResultSet rs = stmt.executeQuery(sql);
            ResultSetMetaData rsmt = rs.getMetaData();

            DefaultTableModel dtm = new DefaultTableModel();
            dtm.addColumn("npm");
            dtm.addColumn("nama");
            dtm.addColumn("usia");
            dtm.addColumn("jenis kelamin");
            dtm.addColumn("jurusan");
            dtm.addColumn("waktu kuliah");

            while (rs.next()){
                dtm.addRow(new Object[]{
                    rs.getString(1),
                    rs.getString(2),
                    rs.getString(3),
                    rs.getString(4),
                    rs.getString(5),
                    rs.getString(6)
                });
            }

            this.closeConn();

            return dtm;

        }

        catch(Exception se){
            se.printStackTrace();
        }
        return null;
    }
}