Is Java really memory safe in the face of races? The case I'm thinking about is this: Shared state: ArrayList A with intial buffer B and length L Thread 1:

Is Java really memory safe in the face of races? The case I'm thinking about is this: Shared state: ArrayList A with intial buffer B and length L Thread 1: Grows A and replaces B with buffer C, length with M Thread 2: (Earlier loaded B into a register) Code says write to A[M-1]. JVM checks M-1 against M but uses B as it was already stored in a register. Now you have a buffer overflow. Except, people on this thread seem to think this is impossible. How does Java prevent this?