readFile.java

public static StringBuilder readFile(File $f) throws IOException {

        StringBuilder   sb =    new StringBuilder();
        BufferedReader  br =    null;
        try {

            String sCurrentLine;
            br = new BufferedReader(new FileReader($f));
            while ((sCurrentLine = br.readLine()) != null) {
                sb.append(sCurrentLine).append("\n");
            }

        } catch (IOException e) {
            throw new IOException("Error leyendo archivo");
        } finally {
            try {
                if (br != null)br.close();
            } catch (IOException ex) {
                throw new IOException("Error cerrando archivo");
            }
        }
        return sb;

    }