高分求解

[sfanpu]

G:\>javac HelloWorld.java
HelloWorld.java:2: package javax.servlet does not exist
import javax.servlet.*;
^
HelloWorld.java:3: package javax.servlet.http does not exist
import javax.servlet.http.*;
^
HelloWorld.java:4: cannot resolve symbol
symbol : class HttpServlet
location: class HelloWorld
public class HelloWorld extends HttpServlet
^
HelloWorld.java:6: cannot resolve symbol
symbol : class HttpServletRequest
location: class HelloWorld
public void doGet(HttpServletRequest request,HttpServletResponse response)th
rows ServletException,IOException
^
HelloWorld.java:6: cannot resolve symbol
symbol : class HttpServletResponse
location: class HelloWorld
public void doGet(HttpServletRequest request,HttpServletResponse response)th
rows ServletException,IOException
^
HelloWorld.java:6: cannot resolve symbol
symbol : class ServletException
location: class HelloWorld
public void doGet(HttpServletRequest request,HttpServletResponse response)th
rows ServletException,IOException

^
6 errors

以上的问题应该怎样解决？