docs: public void removeAllZeros() {
      Iterator<Map.Entry<K, AtomicLong>> entryIterator = map.entrySet().iterator();
      while (entryIterator.hasNext()) {
        Map.Entry<K, AtomicLong> entry = entryIterator.next();
        AtomicLong atomic = entry.getValue();
        if (atomic != null && atomic.get() == 0L) {
          entryIterator.remove();
        }
      }
    }