Illegal operation on empty result set.错误的改正方法

rs = sql.executeQuery("select xh from class where xh =" + n);
  rs.next();
  while(rs.next()) {
  if(rs.getString(1).equals(name)) {
  String a = "update" + "\t" +  tableName + "\t" + "set yhm = " + n +"\t" + "where xh =" + n;
  String b = "update" + "\t" +  tableName + "\t" + "set mm = " + m + "\t" + "where xh =" + n ;
  sql.executeUpdate(a);
  sql.executeUpdate(b); 
  con.close();
  //注册成功，将注册信息传给javabean  然后在另一个jsp页面中进行显示
  zcbean.setBackNews("恭喜你，注册成功！！！");
  zcbean.setUsername(name);  
  zcbean.setPassword(word);    
  RequestDispatcher dispatcher = request.getRequestDispatcher("zcrecord.jsp");
  dispatcher.forward(request, response);  
   }

  } 

当执行rs = sql.executeQuery("select xh from class where xh =" + n);这一句时，你的数据库中没有满足条件的，并且你没有加上while(rs.next()) { }  ,那么此时就会报错。

解决办法：1、改变查询的条件使之满足

    2、加上while(rs.next()) {  }