数组溢出错误java.lang.IndexOutOfBoundsException，在线等

List lista=districtService.getc(district_id);

		StringBuffer s = new StringBuffer();

		for(int i=0;i<lista.size();i++){			

			s.append(lista.get(i)+"-");

		}

		String[] aString=s.toString().split("-");	

		for(int a=0;a<aString.length;a++){

		Pattern pattern = Pattern.compile("=(.+)\\}");

        Matcher matcher = pattern.matcher(aString[a]);

        System.out.println(aString[a]);

        while(matcher.find()) {

            out.print(matcher.group(a)+",");

        }

        }

No group 2

	at java.util.regex.Matcher.group(Unknown Source)

	at com.gpcsoft.srplatform.auth.controller.ExerciseController.eUserAjaxa(ExerciseController.java:69)

	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

	at java.lang.reflect.Method.invoke(Unknown Source)

	at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)

	at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:427)

	at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:415)

	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:788)

	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:717)

	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)

	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:627)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)

	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)

	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)

	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)

	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)

	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)

	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)

	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)

	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)

	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:879)

	at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)

	at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)

	at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)

	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)

	at java.lang.Thread.run(Unknown Source)