По какому принципу работает super.close(); ?

public class TxtInputStream extends FileInputStream {

    public TxtInputStream(String fileName) throws IOException, UnsupportedFileNameException {
        super(fileName);
        if(fileName.endsWith(".txt")){
            char [] b = fileName.toCharArray();
        } else {
            super.close();
            throw new UnsupportedFileNameException();

        }
    }

    public static void main(String[] args) {
    }
}