encoding of I/O

[stone eniac]

Is there no way to know the encoding of a file?
If so,how can I read the file?
I want to find some lines in several .xsl files,but the encoding of these files are different(UTF-8 and UTF-16).
I found I can not read a UTF-16 file use UTF-8 encoding,vice versa.
How can I do with the case?
part code:

BufferedReader bufReader = new BufferedReader(new InputStreamReader(new FileInputStream(file),encoding));
foundStart = false;
while ((!(foundStart))&&((s = bufReader.readLine()) != null)) {
if (s.indexOf(lineStart) != -1) {
foundStart = true;
break;
}
......
}