字符串数组比较？报错！请高手指教！在线,jijiji

[风清扬-3]

我从数据库中取出两个字符串结果集，分别存储在subans,yesans中，执行下代码报错！
可将.equals换成“==”不报错，可结果不正确！
int m=fen.length;
for(int k=0;k<m ;k=k+1){
if(yesans[k].equals(subans[k])) {
defen=defen+fen[k];
}

}
javax.servlet.ServletException
at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:459)
at usdl.student._0002fusdl_0002fstudent_0002fTestResults_0002ejspTestResults_jsp_262._jspService(_0002fusdl_0002fstudent_0002fTestResults_0002ejspTestResults_jsp_262.java, Compiled Code)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java, Compiled Code)
at javax.servlet.http.HttpServlet.service(HttpServlet.java, Compiled Code)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java, Compiled Code)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java, Compiled Code)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java, Compiled Code)
at javax.servlet.http.HttpServlet.service(HttpServlet.java, Compiled Code)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java, Compiled Code)
at org.apache.tomcat.core.Handler.service(Handler.java, Compiled Code)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java, Compiled Code)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java, Compiled Code)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java, Compiled Code)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java, Compiled Code)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java, Compiled Code)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java, Compiled Code)
at java.lang.Thread.run(Thread.java:479)

Root cause:
java.lang.NullPointerException
at usdl.student._0002fusdl_0002fstudent_0002fTestResults_0002ejspTestResults_jsp_262._jspService(_0002fusdl_0002fstudent_0002fTestResults_0002ejspTestResults_jsp_262.java, Compiled Code)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java, Compiled Code)
at javax.servlet.http.HttpServlet.service(HttpServlet.java, Compiled Code)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java, Compiled Code)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java, Compiled Code)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java, Compiled Code)
at javax.servlet.http.HttpServlet.service(HttpServlet.java, Compiled Code)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java, Compiled Code)
at org.apache.tomcat.core.Handler.service(Handler.java, Compiled Code)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java, Compiled Code)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java, Compiled Code)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java, Compiled Code)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java, Compiled Code)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java, Compiled Code)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java, Compiled Code)
at java.lang.Thread.run(Thread.java:479)

[laizg]

haha ...==一般很少人用了。一般都用equals，但可能yesans[k]有为空的(null)所以你就出错了。。给分拉。。：）

[zxhong]

你能保证2个数组元素个数一样且>=m???????

如果不能，请换种方式比较！！！

eg:
for(int k=0;k<yesan.length();k<subans.length() ;k++){
if(yesans[k].equals(subans[k])) {
defen=defen+fen[k];
}

[laizg]

int m=fen.length;
for(int k=0;k<m ;k=k+1){
if(yesans[k].equals(subans[k])) {
defen=defen+fen[k];
}

}
你从这段代码入手，把那个yeasans[k]输出来看看有没有问题先啊。在把subans[k]也输出来看看有没有null先，这样才可以做到查出问题的结果啊。。排除法。

[风清扬-3]

subans,yesans的元素我都看了，都有结果，不为空！和fen的个数保证一致！

[laizg]

subans,yesans的个数一样吗。他们的字符数相同才可以逐个来比较啊。.如果有一个6个,有一个7个,那么第7个比较那时侯就会有一个必然为空字符(null),你这样你知道那两个字符串的值得吗。.你直接这样.
subans="XXXXXX";
yesans="YYYYYY";
然后在比较一下拉。肯定是这两个的问题.