Yes, you need to specify the encoding of the file you want to read.
Yes, this means that you have to know the encoding of the file you want to read.
No, there is no general way to guess the encoding of any given “plain text” file.
The one-arguments constructors of FileReader always use the platform default encoding which is generally a bad idea.
Since Java 11 FileReader has also gained constructors that accept an encoding: new FileReader(file, charset) and new FileReader(fileName, charset).
In earlier versions of java, you need to use new InputStreamReader(new FileInputStream(pathToFile), <encoding>).