照书抄的一段很简单的东西：怎么样都编译不成。

import java.io.*;
import java.servlet.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class  helloworld extends HttpServlet
{
public static void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException
{
response.setContentType("text/html");
PrintWriter out=response.getWriter();
out.println("");
out.println("");
out.println("");
out.println("Hello World!");
out.println("");
out.println("");
out.println("Hello World!");
out.println("");
out.println("");
}
}

显示结果如下：

>javac helloworld.java

>helloworld.java:2: package java.servlet does not exist
import java.servlet.*;
^
helloworld.java:8: cannot resolve symbol
symbol  : class IOException
location: class helloworld
        public static void doGet(HttpServletRequest request,HttpServletResponse
response) throws IOException,ServletException

                 ^
helloworld.java:8: doGet(javax.servlet.http.HttpServletRequest,javax.servlet.ht
p.HttpServletResponse) in helloworld cannot override doGet(javax.servlet.http.H
tpServletRequest,javax.servlet.http.HttpServletResponse) in javax.servlet.http.
ttpServlet; doGet(javax.servlet.http.HttpServletRequest,javax.servlet.http.Http
ervletResponse) and doGet(javax.servlet.http.HttpServletRequest,javax.servlet.h
tp.HttpServletResponse) are static
        public static void doGet(HttpServletRequest request,HttpServletResponse
response) throws IOException,ServletException
                           ^
helloworld.java:11: cannot resolve symbol
symbol  : class PrintWriter
location: class helloworld
                PrintWriter out=response.getWriter();
                ^

同上，首先要建立好支持Servlet的环境，这样才能正确编译Servlet
建议安装tomcat
或使用JBuilder之类的集成开发环境，直接支持Servlet/Ejb等

在classpath里面设置servlet.jar。
servlet.jar并不带在jdk里面，一般tomcat之类的含有。

路径没有设置正确，真的！