为什么我请求转发到到成功页面，但是它跳转到了失败页面。

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


public class loginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        String pwd = req.getParameter("pwd");
        String[] hobby = req.getParameterValues("hobby");
        User user = new User(username, pwd, hobby);

        if (user.getUsername() == "") {
            HttpSession session = req.getSession();
            session.setAttribute("msg", "用户名不能为空");
            resp.sendRedirect("/error.jsp");
        } else if (!"123456".equals(user.getPassword())) {
            HttpSession session = req.getSession();
            session.setAttribute("msg", "密码错误");
            resp.sendRedirect("/error.jsp");
        } else if (user.getHobby() == null) {
            HttpSession session = req.getSession();
            session.setAttribute("msg", "爱好不能为空");
            resp.sendRedirect("/error.jsp");
        } else {
            HttpSession session = req.getSession();
            session.setAttribute("name",user.getUsername());
            session.setAttribute("hobby",user.getHobby());
            req.getRequestDispatcher("/success.jsp").forward(req,resp);
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }

}

你看下是不是条件不满足，传递的参数值为空。