How to read a file in Java with specific character encoding?

Question

I am trying to read a file in as either UTF-8 or Windows-1252 depending on the output of this method:

public Charset getCorrectCharsetToApply() {
    // Returns a Charset for either UTF-8 or Windows-1252.
}

So far, I have:

String fileName = getFileNameToReadFromUserInput();
InputStream is = new ByteArrayInputStream(fileName.getBytes());
InputStreamReader isr = new InputStreamReader(is, getCorrectCharsetToApply());
BufferedReader buffReader = new BufferedReader(isr);

The problem I'm having is converting the BufferedReader instance to a FileReader.

Furthermore:

• The name of the file itself (fileName) cannot be trusted to be a particular Charset; sometime the file name will contain UTF-8 characters, and sometimes Windows-1252. Same goes for the file's content (however if file name and file content will always have matching charsets).
• Only the logic inside getCorrectCharsetToApply() can select the charset to apply, so attempting to read a file by its name prior to calling this method could very well result with, Java trying to read the file name with the wrong encoding...which causes it to die!

Thanks in advance!

Answer 1

So, first, as a heads up, do realize that fileName.getBytes() as you have there gets the bytes of the filename, not the file itself.

Second, reading inside the docs of FileReader:

The constructors of this class assume that the default character encoding and the default byte-buffer size are appropriate. To specify these values yourself, construct an InputStreamReader on a FileInputStream.

So, sounds like FileReader actually isn't the way to go. If we take the advice in the docs, then you should just change your code to have:

String fileName = getFileNameToReadFromUserInput();
FileInputStream is = new FileInputStream(fileName);
InputStreamReader isr = new InputStreamReader(is, getCorrectCharsetToApply());
BufferedReader buffReader = new BufferedReader(isr);

and not try to make a FileReader at all.

Answer 2

Note that if you are using Google Guava, you can use Files.newReader:

final BufferedReader reader =
        Files.newReader(new File(filename), getCorrectCharsetToApply());

Answer 3

With Java 7+, you can create the Reader in one line:

BufferedReader buffReader = Files.newBufferedReader(Paths.get(fileName), getCorrectCharsetToApply());