code: public void excludePackage(String... packageNames) {
          if (packageNames == null) {
              excludePackageNames = null;
          } else {
              for (String packageName : packageNames) {
                  if (excludePackageNames == null) {
                      excludePackageNames = new HashSet<>();
                  }
                  excludePackageNames.add(packageName + PACKAGE_SEPARATOR_CHAR);
              }
          }
      }
docs: Adds packages that this ClassLoader should not handle.
  Any class whose fully-qualified name starts with the name registered here will be handled
  by the parent ClassLoader in the usual fashion.
  
  @param packageNames package names that we be compared against fully qualified package names to exclude