utfstring | UTF-safe string operations in JavaScript | Interpreter library

First, getBytes() returns the bytes of the string in a default charset, which is usually UTF-16. Second, new String(bytes[], string) interpret the bytes as a string in the charset provided, it doesn't convert them. So:

new String(message.getBytes(), "UTF-8")

Try to read a UTF-16 string as UTF-8, bad. Then:

new String(utfString.getBytes(), "WINDOWS-1251")

Try to read the resulting string as WINDOWS-1251, equally bad.

I'm sure at this point your string is destroyed.

You can just call getBytes(Charset) to get the bytes of your string in the charset you want. But in your case you don't even need to do that, because your writeToFile(...) method already does charset conversion when writing to the file, so you can just give it the original message.