String cipherText =""; // for example
BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file), Charset.forName("UTF-8")));
int c;
while((c = reader.read()) != -1) {// read the entire file
  char character = (char) c;
  if (Character.isLetter(character)){ // take only the letters
      cipherText+=character; // append this letter to the string
  }
}
//finally test it
System.out.println(cipherText);

cipherText = cipherText.toUpperCase();