@Override
  public String toString() {
    return "DefaultMemoryManager{" +
           "nativeCapacity: " + nativeCapacityBytes +
           ", heapCapacity: " + heapCapacityBytes +
           ", nativeUsed: " + nativeBytesUsed +
           ", heapUsed: " + heapBytesUsed +
           '}';
  }
@Override
  public String toString()