if (request.getParameter("act").equalsIgnoreCase("save"))这条语句为什么会抛出异常
java.lang.NullPointerException
servlet.ClassManageServlet.doGet(ClassManageServlet.java:65)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
这是为什么?