How to make updating BigDecimal within ConcurrentHashMap thread safe

Question

I am making an application that takes a bunch of journal entries and calculate sum.

Is below way of doing it is thread/concurrency safe when there are multip

Answer 1

Your solution is not thread safe. The reason is that it is possible for a sum to be missed since the operation to put is separate from the operation to get (so the new value you are putting into the map could miss a sum that is being added at the same time).

The safest way to do what you want to do is to synchronize your method.