FileChannel not writing special characters properly

Question

I'm trying to write some text into a file using a FileChannel. So far everything works fine except for the fact that umlauts are not written correctly.

Path fileChannel = Paths.get("c:/channel.txt");
try (FileChannel channel = FileChannel.open(
        fileChannel,
        StandardOpenOption.CREATE,
        StandardOpenOption.READ,
        StandardOpenOption.WRITE)) {

    String response = "Würzburg";
    channel.write(ByteBuffer.wrap(response.getBytes(StandardCharsets.UTF_8)));

}

In this example, I want to write Würzburg into the file, but when I open it, it contains the following: Würzburg. The file itself is utf-8.

Any suggestions, what could be done?

edit:

Finally, I would like to read out the file again, for example like this:

try (FileChannel channel = FileChannel.open(fileChannel, StandardOpenOption.READ)) {

    byte[] buffer = new byte[(int) channel.size()];
    ByteBuffer bb = ByteBuffer.wrap(buffer);
    channel.read(bb);
    String request = new String(buffer, StandardCharsets.UTF_8);
    System.out.println(request);

}

However, a comparison of the strings response and request shows that they are not identical.

Running on a Windows machine, Java 17 (IntelliJ configured with adoptium open jdk)