LongAdderCounter and LongAccumulatorCounter

LongAccumulatorCounter.java

import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.LongAccumulator;

public class LongAccumulatorCounter extends ServerCounter {

    private final AtomicReference<LongAccumulator> accumulator = new AtomicReference<>(
        new LongAccumulator(
            (left, right) -> left + right,
            0L
        )
    );

    @Override
    public void add(long increment) {
        accumulator.get().accumulate(increment);
    }

    @Override
    public long getAndReset() {
        LongAccumulator prev = accumulator.getAndSet(
            new LongAccumulator(
                (left, right) -> left + right,
                0L
            )
        );
        return prev.get();
    }

}

LongAdderCounter.java

import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.LongAdder;

public class LongAdderCounter extends ServerCounter {

    private final AtomicReference<LongAdder> adder = new AtomicReference<>(new LongAdder());

    @Override
    public void add(long increment) {
        adder.get().add(increment);
    }

    @Override
    public long getAndReset() {
        LongAdder prev = adder.getAndSet(new LongAdder());
        return prev.sum();
    }

}