public static void ecriturefichier(String str) throws IOException {
  String ch;
  Scanner sc = new Scanner (System.in);
  System.out.println("donner votre chaine de caractéres :");
  ch=sc.nextLine();
  PrintWriter pw = null;
  try {
    pw = new PrintWriter(new BufferedWriter(new FileWriter(str)));
    do {
      pw.println(ch);
      ch=sc.nextLine();
    } while(!(ch.equals("fin")));
  } finally {
    if (null != fw) fw.close();
  }
}