A code can be divided into a few package/ folder called bean, api, database Connection, function,report, search..
package MyProjectAPI.bean;
public class staff 
{
 private String _staffId;
 private String _staffPassword;
 private String _accessLevel;
 private String _status;
 private String _staffName;
 private String _staffIc;
 private String _staffPhone;
 private String _staffEmail;
 
 public String get_staffId() {
  return _staffId;
 }
 public void set_staffId(String id) {
  _staffId = id;
 }
 public String get_staffPassword() {
  return _staffPassword;
 }
 public void set_staffPassword(String password) {
  _staffPassword = password;
 }
 public String get_accessLevel() {
  return _accessLevel;
 }
 public void set_accessLevel(String level) {
  _accessLevel = level;
 }
 public String get_status() {
  return _status;
 }
 public void set_status(String _status) {
  this._status = _status;
 }
 public String get_staffName() {
  return _staffName;
 }
 public void set_staffName(String name) {
  _staffName = name;
 }
 public String get_staffIc() {
  return _staffIc;
 }
 public void set_staffIc(String ic) {
  _staffIc = ic;
 }
 public String get_staffPhone() {
  return _staffPhone;
 }
 public void set_staffPhone(String phone) {
  _staffPhone = phone;
 }
 public String get_staffEmail() {
  return _staffEmail;
 }
 public void set_staffEmail(String email) {
  _staffEmail = email;
 }
 
 
}
This is example to connect the database with application by using Microsoft Access, javaDB,MySQL.
package MyProjectAPI.datasource;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class ConnectDB 
{
  //driver for JavaDB
  private static String _driver ="org.apache.derby.jdbc.EmbeddedDriver";
  private static String dbName="MyDB";
  private static String connectionURL = "jdbc:derby:" + ConnectDB.dbName + ";create = true";
  
  
  //function for connect to JavaDB
  public static Connection connectDbase() throws ClassNotFoundException, SQLException
  {
   Class.forName(ConnectDB._driver);
   return DriverManager.getConnection(ConnectDB.connectionURL);
  }
  
  //function for connect to Ms. Access
  /*public static Connection connectDbase() throws ClassNotFoundException, SQLException
  {
   Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
   
   String dbPath = "C:\\Program Files\\Apache Software Foundation\\Tomcat 6.0\\webapps\\FTMKIS\\DB\\FTMKIS.mdb";
   //String dbPath = "C:\\DB\\FTMKIS.mdb";
   
   String myDB = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ="+dbPath;
   return DriverManager.getConnection(myDB,"","");
  }*/
  
  
  //driver for MySQL
  /*private static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
  private static String mysql_host = "localhost";
  private static String mysql_user = "root";
  private static String mysql_password = "1234";
  private static String mysql_db = "ftmkis";
  private static final String DATABASE_URL = "jdbc:mysql://localhost/ftmkis";
  function for connect to MySQL
  public static Connection connectDbase() throws ClassNotFoundException, SQLException
  {
   Class.forName(ConnectDB.JDBC_DRIVER);
   return DriverManager.getConnection(ConnectDB.DATABASE_URL,ConnectDB.mysql_user,ConnectDB.mysql_password);
  }*/
  
}
This is example the engine of code use to create, update, view,delete, list,checkpassword, checkId.
package MyProjectAPI.function;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Vector;
import MyProjectAPI.bean.staff;
import MyProjectAPI.datasource.ConnectDB;
public class staffDB
{
 public int checkId(String condition) throws ClassNotFoundException, SQLException
 {
  Connection conn = ConnectDB.connectDbase();
  int updateStatus = 0;
  
  PreparedStatement prep = conn.prepareStatement("SELECT COUNT(_staffId)FROM tbl_staff WHERE _staffId= ?");
  prep.setString(1, condition);
  
  ResultSet resultset = prep.executeQuery();
  while(resultset.next())
  {
   updateStatus = resultset.getInt(1);
  }
  if(conn != null)
   conn.close();
  
  return updateStatus;
 }
 
 public int checkPassword(String _userId, String _password) throws ClassNotFoundException, SQLException
 {
  int updateStatus = 0;
  
  String pass = String.valueOf(_password.hashCode());
  
  Connection conn = ConnectDB.connectDbase();
  
  PreparedStatement prep = conn.prepareStatement("SELECT COUNT(_staffId) FROM tbl_staff WHERE _staffId=? AND _staffPassword = ?");
  
  prep.setString(1, _userId);
  prep.setString(2, pass);
  
  ResultSet resultset = prep.executeQuery();
  
  while(resultset.next())
  {
   updateStatus = resultset.getInt(1);
  }
  if(conn != null)
   conn.close();
   
  return updateStatus;
 }
 public int addStaff(staff Staff)throws SQLException, ClassNotFoundException
 {
  int updateStatus;
  
  Connection conn = ConnectDB.connectDbase();
  
  PreparedStatement prep = conn.prepareStatement("INSERT INTO tbl_staff(_staffId,_staffPassword,_accessLevel," +
    "_status,_staffName,_staffIc,_staffPhone,_staffEmail) VALUES(?,?,?,?,?,?,?,?)");
  
  prep.setString(1, Staff.get_staffId());
  prep.setString(2, Staff.get_staffPassword());
  prep.setString(3, Staff.get_accessLevel());
  prep.setString(4, Staff.get_status());
  prep.setString(5, Staff.get_staffName());
  prep.setString(6, Staff.get_staffIc());
  prep.setString(7, Staff.get_staffPhone());
  prep.setString(8, Staff.get_staffEmail());
  
  updateStatus = prep.executeUpdate();
  
  if(conn != null)
   conn.close();
  
  return updateStatus;
  
 }
 public int updateStaff(staff Staff) throws SQLException, ClassNotFoundException
 {
  int updateStatus;
  
  Connection conn = ConnectDB.connectDbase();
  
  String state = "UPDATE tbl_staff SET";
  state += " _staffPassword = ?,_accessLevel=?,_status=?,_staffName=?,_staffIc=?,_staffPhone=?," +
    "_staffEmail=? WHERE _staffId = ?";
  
  PreparedStatement prep = conn.prepareStatement(state); 
  
  prep.setString(1, Staff.get_staffId());
  prep.setString(2, Staff.get_staffPassword());
  prep.setString(3, Staff.get_accessLevel());
  prep.setString(4, Staff.get_status());
  prep.setString(5, Staff.get_staffName());
  prep.setString(6, Staff.get_staffIc());
  prep.setString(7, Staff.get_staffPhone());
  prep.setString(8, Staff.get_staffEmail());
  
  updateStatus = prep.executeUpdate();
  
  if(conn!=null)
   conn.close();
  
  return updateStatus;
 }
 
 public int updateAdminStatus(String status, String statusvalue, String Staff) throws SQLException, ClassNotFoundException
 {
  int updateStatus;
  
  Connection conn = ConnectDB.connectDbase();
  
  String state = "UPDATE tbl_staff SET "+status+" = ? WHERE _staffId = ?";
  
  PreparedStatement prep = conn.prepareStatement(state);
  
  prep.setString(1, statusvalue);
  prep.setString(2, Staff);
  
  updateStatus = prep.executeUpdate();
  
  if(conn!=null)
   conn.close();
  
  return updateStatus;
 }
 
 public int deleteStaff(String Staff) throws ClassNotFoundException, SQLException
 {
  int updateStatus;
  
  Connection conn = ConnectDB.connectDbase();
  
  PreparedStatement prep = conn.prepareStatement("DELETE FROM tbl_staff WHERE _staffId = ?");
  
  prep.setString(1, Staff);
  
  updateStatus = prep.executeUpdate();
  
  if(conn!=null)
   conn.close();
  
  return updateStatus;
 }
 
 public int resetPassword(String staffId) throws ClassNotFoundException, SQLException
 {
  int updateStatus;
  String pass = String.valueOf("PaS$w0rd1357".hashCode());
  
  Connection conn = ConnectDB.connectDbase();
  
  PreparedStatement prep = conn.prepareStatement("UPDATE tbl_staff SET _staffPassword = ? WHERE _staffId = ?");
  prep.setString(1, pass);
  prep.setString(2, staffId);
  
  updateStatus = prep.executeUpdate();
  
  if(conn!=null)
   conn.close();
  
  return updateStatus;
 }
 public int changePassword(String staffId, String password) throws ClassNotFoundException, SQLException
 {
  int updateStatus;
  String pass = String.valueOf(password.hashCode());
  
  Connection conn = ConnectDB.connectDbase();
  
  PreparedStatement prep = conn.prepareStatement("UPDATE tbl_staff SET _staffPassword = ? WHERE _staffId = ?");
  prep.setString(1, pass);
  prep.setString(2, staffId);
  
  updateStatus = prep.executeUpdate();
  
  if(conn!=null)
   conn.close();
  
  return updateStatus;
 }
 
 public Vector  getStaffList(String condition) throws ClassNotFoundException, SQLException
 {
  Vector  vecStaff = new Vector ();
  
  Connection conn = ConnectDB.connectDbase();
  
  Statement prep = conn.createStatement();
  
  String state = "SELECT * FROM tbl_staff";
  
  if(!condition.equals(null))
   state = "SELECT * FROM tbl_staff "+condition;
  
  ResultSet rs = prep.executeQuery(state);
  
  while(rs.next())
  {
   staff Staff = new staff();
   
   Staff.set_staffId(rs.getString("_staffId"));
   Staff.set_staffPassword(rs.getString("_staffPassword"));
   Staff.set_accessLevel(rs.getString("_accessLevel"));
   Staff.set_status(rs.getString("_status"));
   Staff.set_staffName(rs.getString("_staffName"));
   Staff.set_staffPhone(rs.getString("_staffPhone"));
   Staff.set_staffPhone(rs.getString("_staffPhone"));
   Staff.set_staffEmail(rs.getString("_staffEmail"));
   
   vecStaff.add(Staff); 
  }
  
  if(conn!=null)
   conn.close();
  
  return vecStaff;
 }
}