我在编译BeerSelect.java提示如下错误：

E:wsjJavaWebBeerSelect>javac -d classes srccomexamplewebBeerSelect.java srccomexamplewebBeerSelect.java:3: 错误: 程序包com.example.model不存在 import com.example.model.BeerExpert;                         ^ srccomexamplewebBeerSelect.java:20: 错误: 找不到符号         BeerExpert beerExpert = new BeerExpert();         ^   符号:   类 BeerExpert   位置: 类 BeerSelect srccomexamplewebBeerSelect.java:20: 错误: 找不到符号         BeerExpert beerExpert = new BeerExpert();                                     ^   符号:   类 BeerExpert   位置: 类 BeerSelect 3 个错误  E:wsjJavaWebBeerSelect> E:wsjJavaWebBeerSelect>

我检查BeerSelect.java导入的路径：import com.example.model.BeerExpert;但编译不过，不清楚哪里不对，求教大家能不能帮我看看？ 本人刚在学习servlet相关的。

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目录结构如下：

BeerExpert.java的代码

package com.example.model;  import java.util.ArrayList; import java.util.List;  public class BeerExpert {     public List getBrands(String color){         List brands = new ArrayList();        return (brands);     } }

BeerSelect.java的代码

package com.example.web; import com.example.model.BeerExpert; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.List;  public class BeerSelect extends HttpServlet {     public void doPost(HttpServletRequest request,                        HttpServletResponse response)                throws IOException, ServletException{         response.setContentType("text/html");         PrintWriter out = response.getWriter();         out.println("Beer Selection Advice<br>");         String c = request.getParameter("color");         out.println("<br>Got beer color " + c);         BeerExpert beerExpert = new BeerExpert();         List result = beerExpert.getBrands(c);     } }

系统环境变量：