关于 equals的 疑问，为什么出错误呢？？？？

Question

if ("radioperiod".equals(Scheckrq)) 
{
}
这样写
和
if(Scheckrq.equals("radioperiod"))
都有错误 ，
可能是Scheckrq=null时候的问题，该怎样解决这个问题呢请高手指点一二。谢谢了

Answer 1

if(Scheckrq==null)
{Scheckrq="";}
if(Scheckrq.trim().equals("radioperiod"))
{}

Answer 2

type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
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:256)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.jboss.web.tomcat.security.JBossSecurityMgrRealm.invoke(JBossSecurityMgrRealm.java:220)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.jboss.web.tomcat.tc4.statistics.ContainerStatsValve.invoke(ContainerStatsValve.java:76)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2417)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:65)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:577)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:197)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:781)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:549)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:605)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:677)
at java.lang.Thread.run(Thread.java:534)
root cause java.lang.NullPointerException
at org.apache.jsp.searchtjreport_jsp._jspService(searchtjreport_jsp.java:73)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
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

Answer 3

直接把你的radioperiod打印出来看看是什么

Answer 4

对于任何非空引用x，x.equals(null)应该返回false.
随便说一下，一般情况下，比较对象写equals的左边，只是习惯而已。

Answer 5

Schk_period=request.getParameter("chk_period").trim();
本身就是
radioperiod本身就是
<input type="radio" name="chk_period"   id=chk_period onClick=Showradio() value="radioperiod">
String Scheckrq;
if (Schk_period.length()>=5 )
{
      Scheckrq=Schk_period;
}
else
{
      Scheckrq="";
}是这样的。但是不知道为什么会这样

Answer 6

问题能出在
 Schk_rq=request.getParameter("chk_rq").trim();
 Schk_period=request.getParameter("chk_period").trim();
这里吗
 Schk_rq=request.getParameter("chk_rq").trim();
// Schk_period=request.getParameter("chk_period").trim();
这样就能有一个能运行，疑惑
chk_period和chk_rq是这样的 <input name="chk_rq" type="radio"  id=chk_rq  onClick=Showradion() value="radiorqcheck" checked >
<input type="radio" name="chk_period"   id=chk_period onClick=Showradio() value="radioperiod">

Answer 7

if ("radioperiod".equals(Scheckrq))
{
}
这句没问题，即使Scheckrq=null也不会出错，只是返回falseif(Scheckrq.equals("radioperiod"))
如果Scheckrq=null会出错你的异常代码显示的不是这里的问题，是其它地方出错了

Answer 8

if ("radioperiod".equals(Scheckrq))
{
}
这句没问题，即使Scheckrq=null也不会出错，只是返回false
======================================================同意