最近刚刚开始学习java web 在如下代码的时候提示出了这个错误，我ctrl+shift+o也木有用！代码是书上抄的。求各位java同学解释下。

 package chapter4;


import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MethodTest extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException
    {
        String method = req.getMethod();
        PrintWriter out=resp.getWriter();
        //out.println(method);
        if(method.equals("GET"))
        {
            doGet(req,resp);
        }
        else if(method.equals("POST"))
        {
            doPost(req,resp);
        }
        else
        {
            String errMsg=lStrings.getString("http.method_not_implemented");
        }
    }
}