code: public void failSetApplicationHiddenFor(Collection<String> packagesToFail) {
      if (packagesToFail == null) {
        packagesToFail = Collections.emptySet();
      }
      packagesToFailForSetApplicationHidden = packagesToFail;
    }
docs: Set package names for witch {@link DevicePolicyManager#setApplicationHidden} should fail.
  
  @param packagesToFail collection of package names or {@code null} to clear the packages.