public Counter counter(String name) {
        return getOrAdd(name, MetricBuilder.COUNTERS);
    }
@Test
    public void accessingACustomCounterRegistersAndReusesTheCounter() {
        final MetricRegistry.MetricSupplier<Counter> supplier = () -> counter;
        final Counter counter1 = registry.counter("thing", supplier);
        final Counter counter2 = registry.counter("thing", supplier);

        assertThat(counter1)
                .isSameAs(counter2);

        verify(listener).onCounterAdded("thing", counter1);
    }