去掉PrintWrite

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=utf-8");
        request.setCharacterEncoding("utf-8");
//        ServletContext context= this.getServletContext();
//        PrintWriter out = response.getWriter();
        String name = request.getParameter("username");
        String password =request.getParameter("password");
        String sex =request.getParameter("sex");


//        out.println("用户名：" + name+"<br>");
//        out.println("密码：" + password+"<br>" );
//        out.println("性别：" + sex+"<br>");

        String [] hobbys = request.getParameterValues("hobby");
//        out.println("爱好：");
        for (int i =0; i<hobbys.length;i++) {
//        out.println(hobbys[i]+" ");
        }
        if (name.equals("admin") && password.equals("123456")){
            request.getRequestDispatcher("/success.html").forward(request,response);
        }else {
//            out.println("用户名或密码输入有误...3秒后将自动跳转 <br>");
            response.setHeader("Refresh","3;URL=/error.html");
        }
        }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);

    }
}