InputStreamReader.markSupported is false

Question

I need to “un-read” characters from an InputStreamReader. For that purpose I wanted to use mark and reset but markSupported returns false for the InputStreamReader class, since it doesn’t maintain an internal buffer and/or queue of characters.

I know about BufferedInputStream and PushbackInputStream but neither is appropriate here since they buffer on byte basis, while I need characters.

Does Java offer a buffered character reader which can un-read characters? Actually, let me constrain that further, I only ever need to un-read a single character (for lookahead purposes). Do I really need to maintain my own lookahead?

Answer 1

The two byte-stream based classes java.io.BufferedInputStream and java.io.PushbackInputStream have their character-stream based counterparts in the same package:

java.io.PushbackReader
java.io.BufferedReader

Answer 2

Have you tried java.io.BufferedReader?

Answer 3

You could wrap the input stream using a BufferedReader

Reader markedReader = new BufferedReader(inputStreamReader) ;

The buffered reader does support mark and reads characters.