Please answer this Java question with a very short code.

53. Yo are designing a directory structure for a file system. Each directory can contain files and subdirectories. Write a recursive function calculateTotalSize that takes a Directory object as input and returns the total size (in bytes) of all files within the directory and its subdirectories. The Directory and File classes are defined as follows: class Directory \{ private String name; private List files; private List subdirectories; public List File > getFiles () \{ return files; \} public List getSubdirectories () \{ return subdirectories; \} \} class File \{ private String name; private int size; // Size in bytes public int getsize() \{ return size; \} \}