docs: public static MappedBuffer allocate(File file, FileChannel.MapMode mode, int initialCapacity, int maxCapacity) {
      checkNotNull(file, "file cannot be null");
      checkNotNull(mode, "mode cannot be null");
      checkArgument(initialCapacity <= maxCapacity, "initial capacity cannot be greater than maximum capacity");
      return new MappedBuffer(MappedBytes.allocate(file, mode, initialCapacity), 0, initialCapacity, maxCapacity);
    }