code: @Nullable
      public File getFile(@NotNull final String key) {
          final String file = getString(key);
          if (file == null) {
              return null;
          }
          return new File(file);
      }
docs: Returns a value from the properties file as a File object. If the value
  was specified as a system property or passed in via the -Dprop=value
  argument - this method will return the value from the system properties
  before the values in the contained configuration file.
  
  @param key the key to lookup within the properties file
  @return the property from the properties file converted to a File object