I'm surprised this (is/was) the behaviour of Java. Java doesn't have much (any?) undefined behaviour with simple expressions. I think you only start to get to undefined behaviour when you write programs that are racy according to Java or if you find bugs. And I think this was a very deliberate design decision.

Anyway here is the current JLS which claims the behaviour is defined: https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.htm...

Oh. Never mind I just read the rest of your comment and you linked to the behaviour that is defined :)