Concurrent Modification of HashMap

Question

I have a data structure like below
HashMap <String, HashMap<String, Object>>
Basically its a hashmap within a hash map. Its a global data structure.
I have a timerTask which at every interval iterates the inner hashMap and Modifies an attribute in the Object (Say Decrements an Integer attribute in the Object)
This will be continuing.
While the iteration is in progress inside the TimerTask, if i try to Modify the HashMap from outside via some other method call, I receive a concurrent Modification Exception.
My Question is, How to over come this Problem of managing both the things concurrently?

Answer 1

wizsen wrote:
HashMap <String, HashMap<String, Object>>
Basically its a hashmap within a hash map.That's a bad idea. You almost certainly will want to encapsulate it in one way or another. You probably want a custom class to hold that structure.
Its a global data structure.What does that mean?
My Question is, How to over come this Problem of managing both the things concurrently?Avoid accessing the data structure from two places at the same time. Possibly using synchronization.