没解决的很简单的有关问题

没解决的很简单的问题
为什么下面的两个类，我放入了同一个包准备编译TestServlet.java时总是报错！！！！！！

package test;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class TestServlet extends HttpServlet{
public void doGet(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
String username=request.getParameter("username");
UserManager userManager=new UserManager();
userManager.add(username);
request.getRequestDispatcher("add_success.jsp").forward(request,response);
}
public void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
doGet(request,response);
}}

package test;
public class UserManager{
public void add(String username){
System.out.println("UserManager.add() -->>>>>> username:"+username);
}}

[解决办法]

Java code

String username=(String)request.getParameter("username");//看看这句，改后的
[解决办法]
看一下构造函数对吗？是不是覆盖了一个有参数的？自己写个
public UserManager（）{}试试
[解决办法]
Java code
package test;public class UserManager{//改成class UserManager{