帮我看一下下面创建jdbc连接怎么会出错

String driverClasses=com.microsoft.jdbc.sqlserver.SQLServerDriver;
try {
       Driver driver = (Driver)Class.forName(driverClasses).newInstance();//这一步了错了
       DriverManager.registerDriver(driver);
       drivers.addElement(driver);
}
   catch (Exception e) {
       Log.printEvent("Can't register JDBC driver: " +
                  driverClassName + ", Exception: " + e,logFile);
}