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标 题Re: [问题] 请问有关JSP阵列的问题...
发信站SayYA 资讯站 (Thu Aug 31 18:17:55 2006)
转信站ptt!ctu-reader!news.nctu!SayYa
※ 引述《[email protected] (kandy)》之铭言：
> <%
> String back_check[]=request.getParameterValues("yron");
> String back_ins_no[]=request.getParameterValues("ins_no");
[-----------]
这种写法，不是翻到了古书。就是之前在学别的语言转不过来XD
String[] foo的写法比较好，也不会因为不同的ide出现不同莫名奇妙的error
> int i;
[----] 如果没有特殊用途，local value尽量一开始就初始
可以写在for之中 for(int i=0;...........)
> int size=9;
> for(i=0;i<size;i++)
> {
> if(back_check[i].equals("checked"))
[-----------] 你有把握每一个element都不是null吗?
null的reference是不能被呼叫的。
来个简单的实验
public class NullCall {
public static void main(String[] args) {
String x = null;
x.equals("3");
}
}
=============================================
Exception in thread "main" java.lang.NullPointerException
at NullCall.main(NullCall.java:4)
> {
> out.println("back_ins_no[i]");
> }
> }
> %>
> ==========================================
> 执行後出现这讯息:
> HTTP Status 500 -
> --------------------------------------------------------------------------------
> type Exception report
> message
> description The server encountered an internal error () that prevented it
> from fulfilling this request.
> exception
> org.apache.jasper.JasperException: Exception in JSP: /Management/do.jsp:15
> 12: int size=9;
> 13: for(i=0;i<size;i++)
> 14: {
> 15: str=back_check[i];
> 16: if(str.equals("checked"))
> 17: {
> 18: out.println("back_ins_no[i]");
> Stacktrace:
> org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:504)
> org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
> org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
> org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
> root cause
> java.lang.NullPointerException
> org.apache.jsp.Management.do_jsp._jspService(do_jsp.java:61)
> org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
> org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
> org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
> org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
> ========================================================================
> 请教各位前辈该怎麽解决,另外还有个问题..就是arrary的阵列个数要如何取得?
> 感谢大家!
*大惊*
array是java最初级物件了他有一个属性是存长度的length
快找书去认识一下吧
> note The full stack trace of the root cause is available in the Apache
> Tomcat/5.5.17 logs.
> --------------------------------------------------------------------------------
--
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