如何跟踪哪个HashMap抛出ConcurrentModificationException

Question

In my application I have several HashMaps. One of them do throw ConcurrentModificationException every now and then. Problem is that I do not know how to trace which Map actually throws it, and when the ConcurrentModification happens. The stack trace does not show any line numbers to where it happens. The begin of the stack trace looks liks this:

java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:806)
at java.util.HashMap$ValueIterator.next(HashMap.java:838)
at com.parse.ParseTraverser.traverseInternal(ParseTraverser.java:87)
at com.parse.ParseTraverser.traverse(ParseTraverser.java:137)
at com.parse.ParseObject.collectFetchedObjects(ParseObject.java:817)
at com.parse.ParseObject.access$700(ParseObject.java:49)
at com.parse.ParseObject$13.then(ParseObject.java:1487)
at com.parse.ParseObject$13.then(ParseObject.java:1484)
at bolts.Task$15.run(Task.java:917)
at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:105)
at bolts.Task.completeAfterTask(Task.java:908)
at bolts.Task.continueWithTask(Task.java:715)

Answer 1

如果您不能评估通过两个操作同时修改了哪个HashMap （经典示例是循环中的删除），则可以始终使用ConcurrentHashMap 。