InputStream and Reader subclass hierarchy difference [closed]

The InputStream abstract class has FileInputStream and FilterInputStream as a direct subclass. FileInputStream has all necessary code to establish an input connection from a file, whereas FilterInputStream is created as a wrapper which acts as a decorator and facilitates other classes extending it to provide a specific and specialized operation on InputStream, hence BufferedInputStream is a subclass of it and provide buffering capabilities by introducing an in-memory byte-array which acts as a storage for reducing System input calls directly to the file-system. This complete hierarchy makes sense.


pictorial representation -
InputStream ---> FileInputStream
|
|
---> FilterInputStream ---> BufferedInputStream



But then the Reader abstract class has FilterReader as a direct subclass but FileReader is not a direct subclass, FileReader extends InputStreamReader, and BufferedReader is a direct subclass of Reader and not of FilterReader, again why this decision is taken.


pictorial representation of this as well
Reader ---> InputStreamReader ---> FileReader
|
---> FilterReader
|
---> BufferedReader



Let me summarize all my queries in bullet pointers for easy answering -



* Why BufferedReader is a direct subclass of Reader and not extend FilterReader, as in the InputStream hierarchy.

* Why does FileReader extend InputStreamReader and not directly a subclass of Reader ?

* What capabilities were given to InputStreamReader because of which FileReader was kept a subclass of it?

* Why are those capabilities of InputStreamReader not given to FilterReader? If it was done that way, maybe the Reader abstract class might have the same hierarchy as InputStream.

* FilterReader might have been designed such that InputStreamReader can extend it and then provide an extra specialised wrapper on Reader for input-stream-specific purposes, which then can be further utilized. Why keep it a direct subclass instead?