这一行抛出了异常，向各位请教？

<%@ page import="java.io.* " %>
<%@ page import="java.sql.* " %>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page contentType="text/html;charset=UTF-8" %>
<html>
  <head>
    <title>DbJSP.jsp</title>
  </head>
  <body>
    <% 
       //try
      // {
          Connection con;
          Statement stmt;
          ResultSet rs;
          //加载MySQL的驱动程序
           Class.forName("com.mysql.jdbc.Driver");
          //注册MySQL的驱动程序
           DriverManager.registerDriver(new com.mysql.jdbc.Driver());
          //用适当的驱动程序连接到数据库
           String dbUrl="jdbc:mysql://localhost:3306/BookDB?useUnicode=true&characterEncoding=UTF-8";
          String dbUser="root";
          String dbPwd="1234";
          //建立数据库链接
          con=java.sql.DriverManager.getConnection(dbUrl,dbUser,dbPwd);
          //创建一个JDBC声明
          stmt=con.createStatement();
          //增加新记录
          stmt.executeUpdate("INSERT INTO books(id,name,title,price) VALUES('999','TOM','Tomcat',44.5)");
          //查询记录
          rs=stmt.executeQuery("SELECT id,name,title,price from books");
          //输出查询结果
          out.println("<table border=1 width=400>");
          while(rs.next())
          {
            String col1=rs.getString(1);
            String col2=rs.getString(2);
            String col3=rs.getString(3);
            float col4=rs.getFloat(4);
            out.println("<tr><td>"+col1+"</td><td>"+col2+"</td><td>"+col3+"</td><td>"+col4+"</td><tr>");
          }
          out.println("<table>");
          //删除新增加的记录
          stmt.executeUpdate("DELETE FROM books WHERE id='999' ");
          //关闭数据库链接
          rs.close();
          stmt.close();
          con.close();
         //}
         //catch(Exception e)
         //{out.print(e.getMessage());}
        %>
  </body>
</html>