迭代器，但仍为ConcurrentModificationException

Question

全部，

遇到ConcurrentModificationException问题，很难找到解决方案，部分原因是我在迭代列表时看不到我在哪里修改列表…有什么想法吗？？我已经强调了导致问题的那一行(it3.remove(((。这一行真的停滞不前。。

编辑：Stacktrace:

Exception in thread "Thread-4" java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
    at java.util.ArrayList$Itr.next(Unknown Source)
    at com.shimmerresearch.advancepc.InternalFrameAndPlotManager.subtractMaps(InternalFrameAndPlotManager.java:1621)

第1621行对应于我上面引用的代码中的it3.remove((。

private void subtractMaps(ConcurrentSkipListMap<String, PlotDeviceDetails> firstMap, ConcurrentSkipListMap<String, PlotDeviceDetails> secondMap) {
    // iterate through the secondmap
    Iterator<Entry<String, PlotDeviceDetails>> it1 = secondMap.entrySet().iterator();
    while (it1.hasNext()) {
        Entry<String, PlotDeviceDetails> itEntry = (Entry) it1.next();
        String mapKey = (String) it1Entry.getKey();
        PlotDeviceDetails plotDeviceDetails = (PlotDeviceDetails)it1Entry.getValue();
        // if we find an entry that exists in the second map and not in the first map continue
        if(!firstMap.containsKey(mapKey)){
            continue;
        }
         // iterate through a list of channels belonging to the secondmap
        Iterator <PlotChannelDetails> it2 = plotDeviceDetails.mListOfPlotChannelDetails.iterator(); 
        while (it2.hasNext()) {
            PlotChannelDetails it2Entry = it2.next();
            // iterate through a list of channels belonging to the firstmap
            Iterator <PlotChannelDetails> it3 = firstMap.get(mapKey).mListOfPlotChannelDetails.iterator();
            innerloop:
            while(it3.hasNext()){
                // if a channel is common to both first map and second map, remove it from firstmap
                PlotChannelDetails it3Entry = it3.next();
                if(it3Entry.mChannelDetails.mObjectClusterName.equals(it2Entry.mChannelDetails.mObjectClusterName)){
                    it3.remove(); // this line is causing a concurrentModificationException
                    break innerloop;
                }
            }
        }
    }
}

Answer 1

plotDeviceDetails.mListOfPlotChannelDetails和firstMap.get(mapKey).mListOfPlotChannelDetails引用相同的列表。

plotDeviceDetails和firstMap.get(mapKey)是否也引用同一对象是未知的，没有更多信息，但它们共享频道列表。

Answer 2

堆栈跟踪显示mListOfPlotChannelDetails是ArrayList，并且由于堆栈跟踪还显示错误来自it3.remove()，并且代码中没有任何内容可以导致这种情况，因此您确实面临并发修改，即另一个线程更新了it3迭代的ArrayList。

请记住，ArrayList不支持并发多线程访问。