public void processCommand(String command, String content, boolean hasFolloingCommand) {
	......
    else if (command.equalsIgnoreCase("RNFR")){
        String data51= content.substring(5);
        data51=data51.trim();
        processRenameFromCommand(data51);
    }
    else if (command.equalsIgnoreCase("RNTO")){
        String data51= content.substring(5);
        data51=data51.trim();
        processRenameToCommand(data51);
    }
	..........
}

/**
   *  Process the rename command
   */
    private void processRenameFromCommand(String data51){
      if (!allowWrite){ // A boolean that I added in the case where writing to the server is not authorized
        binaryStringSender.sendStringInBinaryMode("550 Writing permission not granted.");
        return;
      }
      Log.d("renameCommandFrom","data51 "+data51);
      Log.d("renameCommandFrom","rootDirectory "+rootDirectory);
      Log.d("renameCommandFrom","currentWorking "+currentWorkingDirectory);
      currentWorkingDirectory = currentWorkingDirectory.replace("//","/");
      // add a field oldPath
      if (data51.startsWith("/")){
        this.oldPath = rootDirectory.getPath() +data51;
      }else {
        this.oldPath = rootDirectory.getPath() + currentWorkingDirectory+"/"+data51;
      }
      Log.d("renameCommand","oldPath "+oldPath);
      binaryStringSender.sendStringInBinaryMode("350 File to rename: "+currentWorkingDirectory+"/"+data51);
    }

  /**
   *  Process the rename command
   */
  private void processRenameToCommand(String data51){
    Log.d("renameCommandTo","data51 "+data51);
    String newPath = rootDirectory.getPath()+data51;
    Log.d("renameCommandTo","newPath "+newPath);
    if (renameFile(this.oldPath,newPath)){
      binaryStringSender.sendStringInBinaryMode("250 Success! renamed to: "+data51);
    }else {
      binaryStringSender.sendStringInBinaryMode("500 Failed! renamed to: "+data51);
    }

  }

  public static boolean renameFile(String oldFileName, String newFileName) {
    File oldFile = new File(oldFileName);
    File newFile = new File(newFileName);

    if (oldFile.exists()) {
      boolean success = oldFile.renameTo(newFile);
      return success;
    } else {
      return false; // Le fichier source n'existe pas.
    }
  }