1、错误描写叙述

java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.util.Map	at service.impl.BillServiceImpl.exportBillExcel(BillServiceImpl.java:336)	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)	at java.lang.reflect.Method.invoke(Method.java:606)	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)	at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:52)	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)	at com.sun.proxy.$Proxy46.exportBillExcel(Unknown Source)	at controller.BillController.exportBillExcel(BillController.java:159)	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)	at java.lang.reflect.Method.invoke(Method.java:606)	at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)	at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)	at com.skycloud.oa.filter.TranscationFilter.doFilter(TranscationFilter.java:32)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)	at com.skycloud.oa.filter.ContentFilter.doFilter(ContentFilter.java:57)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)	at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)	at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)	at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)	at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)	at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)	at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)	at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)	at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)	at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)	at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)	at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)	at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)	at java.lang.Thread.run(Thread.java:745)

2、错误原因

List
     
      
     

Map
     
       map=(Map
      
       ) itemList.get(i);
      
     

   

  itemList是一个List集合，而且它里面还有个List。将List<List>强转成Map，导致报错

3、解决的方法

List