docs: public static Exception checkFile(final File file)
  	{
  		Exception ex = null;
  		String error = null;
  		// check if the file does not exists...
  		if (!file.exists())
  		{
  			error = "The " + file + " does not exists.";
  			ex = new FileDoesNotExistException(error);
  			return ex;
  		}
  		// check if the file is not a directory...
  		if (!file.isDirectory())
  		{
  			error = "The " + file + " is not a directory.";
  			ex = new FileIsNotADirectoryException(error);
  			return ex;
  		}
  
  		final File[] ff = file.listFiles();
  		// If the file is null
  		if (ff == null)
  		{ // it is security restricted
  			error = "The " + file + " could not list the content.";
  			ex = new DirectoryHasNoContentException(error);
  		}
  		return ex;
  	}