java.util.concurrent.atomic · java.base · since Java 1.8

LongAdder

declaration

public class LongAdder extends Striped64 implements Serializable

Contention-striped counter: increments hit per-thread cells, sum() aggregates. Beats AtomicLong decisively for hot write-mostly counters (metrics, hit counts).

Key methods

`void increment() / void add(long x)`	Nearly contention-free writes.
`long sum()`	Aggregate — weakly consistent under concurrent writes (fine for stats).