docs: private static String jarFileName() {
          // do this first so we can access extractor, ok to invoke more than once
          createExtractor();
          // get <name> from path/<name>.jar
          String fullyQualifiedFileName = extractor.container.getName();
          int lastSeparator = fullyQualifiedFileName.lastIndexOf(File.separatorChar);
          String simpleFileName = fullyQualifiedFileName.substring(lastSeparator + 1);
          int dotIdx = simpleFileName.lastIndexOf('.');
          if (dotIdx != -1) {
              return simpleFileName.substring(0, simpleFileName.lastIndexOf('.'));
          }
          return simpleFileName;
      }