Connection conn=null;
  PreparedStatement pStat=null;
  ResultSet rs=null;
  try{
    conn=DBC.getConnection();
    pStat=conn.prepareStatement("select NCPM,CPM from ClassT where CNO='"+Class.getCNO()+"'");
    rs=pStat.executeQuery();
    if(rs.next())
     {
         out.print(rs.getString(1));
         out.print(rs.getString(2));
     Class.setNCPM(rs.getString(1));
     Class.setCPM(rs.getString(2));
      if(rs.getString(1).compareTo(rs.getString(2))==0)
            response.sendRedirect("jsp3.jsp");
         else response.sendRedirect("jsp4.jsp");
       }  }catch(Exception ex){
    ex.printStackTrace();
  }finally{
    if(rs!=null) rs.close();
    if(pStat!=null) pStat.close();
    if(conn!=null) conn.close();
  }
jsp4代码 
int i;
  Connection conn=null;
  PreparedStatement pStat=null;
  ResultSet rs=null;
  try{
    conn=DBC.getConnection();
    pStat=conn.prepareStatement("select COUNT(*) from SClassT  where SNO='"+Users.getUserName()+"' AND CTR='"+Class.getCTR()+"'");
    rs=pStat.executeQuery();
    if(rs.next())
     {
      i=Integer.parseInt(rs.getString(1));
       if(i==2)
       {
               response.sendRedirect("jsp5.jsp");
       }
         else response.sendRedirect("sclassinsert.jsp");
      }
  }catch(Exception ex){
    ex.printStackTrace();
  }finally{
    if(rs!=null) rs.close();
    if(pStat!=null) pStat.close();
    if(conn!=null) conn.close();
  }
以上是关于选课系统中选课门数的代码,我设置的是限制每人只能选2门,可是运行时却没起作用,麻烦哪位帮我看看