DB---->屏幕

 DB-->屏幕：          public static void main(String[] args){    

                                    String url ="jdbc:mysql://localhost/bookdb";   

                                   String username = "dbuser";     

                                   String password = "1234";  

                                   String sql = "select name from customers where cid>=4";  

                                   try {    Class.forName("org.gjt.mm.mysql.Driver").newInstance();  

                                  } catch (InstantiationException e1) {  

                                   e1.printStackTrace();  

                                   } catch (IllegalAccessException e1) {    e1.printStackTrace();  

                                   } catch (ClassNotFoundException e1) {    e1.printStackTrace();

                                   }  try {    Connection conn= DriverManager.getConnection(url,username,password);    

                                                  PreparedStatement pstmt = conn.prepareStatement(sql);   

                                                  ResultSet rs = pstmt.executeQuery();  

                                                   while(rs.next()){  

                                                   System.out.println(rs.getString("name"));}   

                                                   pstmt.close();  

                                                   conn.close();  

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

特别说明：ResultSet类是一种集合，里面保存了每一条JDBC获取到的记录。当执行rs.next()时，rs会自动去找下一条记录（rs默认从第一条记录开始）。