FAQ（80）：java.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification

版权声明： https://blog.csdn.net/qq_29166327/article/details/82258293

2018年8月31日

1、日志：

2018-04-13 20:00:55.757:WARN:oejs.ServletHandler:/g01-web/admin/activityManager/sendActivity.jsp
java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
	at java.util.ArrayList$Itr.next(ArrayList.java:831)
	at org.apache.jsp.admin.activityManager.sendActivity_jsp._jspService(sendActivity_jsp.java:146)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:403)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:492)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:378)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
	at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:684)
	at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:501)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:137)
	at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:557)
	at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:231)
	at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1086)
	at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:428)
	at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:193)
	at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1020)
	at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:135)
	at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
	at org.eclipse.jetty.server.Server.handle(Server.java:370)
	at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:494)
	at org.eclipse.jetty.server.AbstractHttpConnection.content(AbstractHttpConnection.java:982)
	at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.content(AbstractHttpConnection.java:1043)
	at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:865)
	at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:240)
	at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:667)
	at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
	at java.lang.Thread.run(Thread.java:745)

2、解决方法：

1）线程的bug；
源码：
（在遍历对象时，同时修改对象的数据）

        for(ActivityInfo info : list){
            if(info.getActivityId() == Integer.parseInt(activityId)){
                System.out.println("del-info:"+info);
                list.remove（info);
                accountService.notifyLogonPlayerActivity(ActivityNotifyType.FORCE_ACTIVITY.getCode(),info.getActivityId());
                break;
            } 
        }

2）修改：

        for(ActivityInfo info : list){
            if(info.getActivityId() == Integer.parseInt(activityId)){
                System.out.println("del-info:"+info);
                delActivity = info;
                accountService.notifyLogonPlayerActivity(ActivityNotifyType.FORCE_ACTIVITY.getCode(),info.getActivityId());
                break;
            } 
        }
        list.remove(delActivity); 

改为：跳出循环体后再修改对象。

3）foreach的快速失败，

阿里巴巴java开发手册建议：

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7. 【强制】不要在 foreach 循环里进行元素的 remove / add 操作。 remove 元素请使用 Iterator
方式，如果并发操作，需要对 Iterator 对象加锁。

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