<p>I'm using the MIDP 2.0 (JSR 118) and I just noticed that there is no reader for strings in J2ME.</p>

<p>Does anyone know how you are supposed to read Strings from an <code>InputStream</code> or <code>InputStreamReader</code> in a platform independent way (i.e. between two java enabled cell phones of different models)?</p>

Which profile are you using? The MID profile in JSR 118 specifies
InputStreamReader
(not StringReader, but that wouldn't help you read from an InputStream anyway).
EDIT: To reflect the change to the question :)
You use InputStreamReader.read(char[], int, int) and when you've read all you want to, create a new string from a char array. If you want to read a line at a time as you would from BufferedReader, you basically need to implement the functionality of BufferedReader yourself (keeping a buffer of "read but not consumed" chars) and keep reading until you hit a line break.