Common Java Streams Mistakes (part 4): Sharing Unsynchronized Mutable State in Java Parallel Streams

This video analyzes implementations of various ways of computing factorials for BigIntegers to demonstrate the performance of alternative parallel and sequential algorithms, as well as the dangers of sharing unsynchronized state between threads.

[timwalters]

If there was a MutableBigInteger, it might be faster to use mutable reduction (aka collect()) as it would save on creating a BigInteger for every intermediate result..

[timwalters]

Does the get() method on the synchronised solution need to be synchronised? Seems like the get method is only being called after the stream processing has been completed.