高分求教很菜的问题（不好意思哦~~~~~）__StandardPipeline_java_apache_catalina_org_

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高分求教很菜的问题（不好意思哦~~~~~）

来源: 互联网发布时间：2015-11-01

本文导语: 下面的代码是我从表单中获取变量的值，然后转化为整型，为什么会出错呢？ String cate; cate =request.getParameter("incate"); int intincate=java.lang.Integer.parseInt(cate); 如果直接获取整型也是同样的问题 ...

下面的代码是我从表单中获取变量的值，然后转化为整型，为什么会出错呢？
         String cate;
cate =request.getParameter("incate");
int intincate=java.lang.Integer.parseInt(cate);

如果直接获取整型也是同样的问题
         int cate=(int)request.getParameter("incate");

错误提示如下：
java.lang.NumberFormatException: null
at java.lang.Integer.parseInt(Integer.java:373)
at java.lang.Integer.parseInt(Integer.java:454)
at org.apache.jsp.person$jsp._jspService(person$jsp.java:277)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:201)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:381)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:473)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:468)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.ajp.tomcat4.Ajp13Processor.process(Ajp13Processor.java:458)
at org.apache.ajp.tomcat4.Ajp13Processor.run(Ajp13Processor.java:551)
at java.lang.Thread.run(Thread.java:484)

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请大虾赐教！

获得的变量为NULL
当然会出错
cate =request.getParameter("incate");
if(cate!=null){

int intincate=java.lang.Integer.parseInt(cate);
}

楼上的有问题。应该是。
if(cate.equals("")!=true)
{
int intincate=java.lang.Integer.parseInt(cate);
}