Question

我在向列表中添加新项目时遇到问题，因为它会覆盖旧项目而不是显示在旧元素下。

我该怎么做才能正确地在旧元素下添加一个新元素，并一键删除所有元素，但是每个新添加的元素都应该出现在旧元素之后，而不是替换它

我的代码：

@WebServlet(name = "HttpSessionServlet", urlPatterns = {"/HttpSessionServlet"})
public class HttpSessionServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

    HttpSession session = request.getSession();

    ArrayList notes = (ArrayList)session.getAttribute("notes");
    if (notes == null) {
    notes = new ArrayList ();
    session.setAttribute("notes",notes);
    session.invalidate();
    }

    String note = request.getParameter("note");
    if (note != null){
       notes.add(note);
       notes.remove("note");
    }


    PrintWriter out = response.getWriter();

    out.println("<html>"); out.println("<body>");
    out.println("<h1>My notes</h1>");
    out.println("<ul>");

    for (int i = 0; i < notes.size(); i++)
    out.println("<li>" + notes.get(i));

    out.println("</ul>");

    out.println("<form action='HttpSessionServlet'>");
    out.println("<input type='text' name='note'/><br/>");
    out.println("<input type='submit' value='Add note'/>");
    out.println("</form>");
    out.println("<form action='HttpSessionServlet'>");
    out.println("<input type='submit' value='Delete'/>");
    out.println("</form>");
    out.println("</body>");
    out.println("</html>");
    }
}

如何在旧元素下正确添加一个新元素？

0 个答案: