DB(){
        try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            
            String dbf="E:\\大学\\数据库\\Text.accdb";  //连接一个access数据库
             String dburl = "jdbc:odbc:driver={Microsoft Access Driver (*.mdb,*.accdb)};DBQ=" + dbf;
            conn = DriverManager.getConnection(dburl,"","");
            
            
            stmt = conn.createStatement();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
//            
            e.printStackTrace();
        }
    }
错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at sun.jdbc.odbc.JdbcOdbcDriver.initialize(JdbcOdbcDriver.java:436)
    at sun.jdbc.odbc.JdbcOdbcDriver.connect(JdbcOdbcDriver.java:153)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");  什么意思