code: private String getDefaultPackageExtension() {
  
          // Default package format on z/OS is a pax
          if ("z/OS".equalsIgnoreCase(bootProps.get("os.name"))) {
              return "pax";
          }
  
          if (PackageProcessor.IncludeOption.RUNNABLE.matches(includeOption)) {
              return "jar";
          }
  
          return "zip";
      }
docs: Determine the default package format for the current operating system.
  
  @return "pax" on z/OS and "zip" for all others