按照老师的代码，出现空指针异常，怎么办？

Question

HTTP Status 500 - java.lang.NumberFormatException: nulltype Exception reportmessage java.lang.NumberFormatException: nulldescription The server encountered an internal error that prevented it from fulfilling this request.exceptionorg.apache.jasper.JasperException: java.lang.NumberFormatException: null org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:555) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)root causejava.lang.NumberFormatException: null java.lang.Integer.parseInt(Unknown Source) java.lang.Integer.parseInt(Unknown Source) org.apache.jsp.details_jsp._jspService(details_jsp.java:174) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)note The full stack trace of the root cause is available in the Apache Tomcat/8.0.28 logs.

Answer 1

这是数字格式异常，不是空指针异常，应该是在转型的时候出的问题，比如数字转字符串或者字符串转数字时候出了问题。仔细检查相应部分代码。

Answer 2

这是哪一个章节的课程？我帮你看看