[Input|Output]Streams exist since JDK1.0, while their character-counterparts Readers|Writers exist since JDK1.1.
Most concepts seem similar, with one exception: the base classes of streams declare an abstract method which processes one single byte at a time, while base readers/writers classes declare an abstract method which processes whole char-arrays.
Thus, given that I understand it correctly, every overridden stream class is limited to process single bytes (thereby performing at least one method call for each byte!), while overridden readers/writers only need a method call per array(-buffer).
Isn't that a huge performance problem?
Can a stream be implemented as subclass of either InputStream or OutputStream, but nevertheless be based on byte-arrays?
Actually, subclasses of InputStream have to override the method that reads a single byte at a time, but also can override others methods that read while byte-arrays. I think that's actually the case for most of the Input/Output streams.
So this isn't much of a performance problem, in my opinion, and yes, you can extend Input/Output stream and be based on byte-arrays.