Regarding Java’s data races, they are “safe” as well for 32bit primitives and references (and in practice for 64bit primitives as well, but that is not spec-mandated). They offer no-out-of-thin-air protections, meaning that you can only observe values that were explicitly set by a thread. A prototypical example would be a non thread-safe counter being simultaneously incremented from many threads - in java it is guaranteed to have a value between 0 and the true count.