■ FilterReader is an abstract class providing default method implementations for people wishing to write their own stream filtering classes. In such a case, it can be handier to extend FilterReader rather than Reader, as FilterReader already has all concrete method implementations. FilterReader is intended to act as a superclass for character input streams that read data from some other character input stream, filter it in some way, and then return the filtered data when their own read( ) methods are called.
■ Since FilterReader doesn't provide any useful I/O functionality at the target level of this site, no further explanations or examples of FilterReader are provided here. see Reader class