code: public final boolean isFileExcludedByExtension(@Nullable final File file) {
      return file == null || !file.isFile() || this.excludeExtensions.contains(PreprocessorUtils.getFileExtension(file));
    }
docs: Check that a file is excluded from preprocessing and coping actions
  
  @param file a file to be checked
  @return true if th file must be excluded, otherwise false