getAndIncrement

GetAndIncrement is an atomic operation commonly provided by concurrent programming libraries. It returns the current value of an atomic numeric object and then increments that value by one, all as a single indivisible step. This atomicity ensures that no interleaving thread observes a partial update and that the increment is immediately visible to all threads.

In practice, getAndIncrement is used when the previous value is needed and the sequence must advance safely across threads. For example, in Java’s AtomicInteger, a call to getAndIncrement returns the value before the increment and updates the stored value atomically. If the counter starts at 5, counter.getAndIncrement() yields 5 and the counter becomes 6. By contrast, incrementAndGet would perform the increment first and then return the new value.

Semantics and behavior: the operation is thread-safe and lock-free in typical implementations, relying on low-level primitives such as compare-and-swap. The exact performance characteristics depend on contention: higher contention can reduce throughput due to repeated CAS retries, but the operation remains non-blocking and linearizable.

Common uses include counting in multithreaded scenarios, generating unique sequence numbers, and implementing thread-safe indices or IDs. GetAndIncrement is often contrasted with methods that return the updated value after incrementing, highlighting an important distinction in control flow and value semantics.