code: public Jar addEntries(String path, Path dirOrZip, Filter filter) throws IOException {
          return addEntries(path != null ? Paths.get(path) : null, dirOrZip, filter);
      }
docs: Adds a directory (with all its subdirectories) or the contents of a zip/JAR to this JAR.
  
  @param path     the path within the JAR where the root of the directory/zip will be placed, or {@code null} for the JAR's root
  @param dirOrZip the directory to add as an entry or a zip/JAR file whose contents will be extracted and added as entries
  @param filter   a filter to select particular classes
  @return {@code this}