[pvg]

That would be a very clunky approach to put it mildly - the explicit design intent of BufferedReader is to let you read lines without caring what the line separator is - it's a lossy transformation. You also can't subclass String. You'd be adding something very unwieldy for an edge case that is directly contrary to the purpose of the API. The 'mistake' (such as it is) of the author here is simply using the wrong API - there are shorter, more direct ways to read a file into a string without any of these contortions.

    data = new String(Files.readAllBytes(Paths.get(filename)));