Is Java ArrayList / String / atomic variable reading thread safe?

Question

I\'ve been mulling this over & reading but can find an absolute authoritative answer.

I have several deep data structures made up of objects containing ArrayLists, S

Answer 1

Just as an addendum to everyone else's answers: if you're sure you need to synchronize your array lists, you can call Collections.synchronizedList(myList) which will return you a thread safe implementation.