code: @Override
      public CRLReason getRevocationReason() {
          Extension ext = getExtension(PKIXExtensions.ReasonCode_Id);
          if (ext == null) {
              return null;
          }
          CRLReasonCodeExtension rcExt = (CRLReasonCodeExtension) ext;
          return rcExt.getReasonCode();
      }
docs: This method is the overridden implementation of the getRevocationReason
  method in X509CRLEntry. It is better performance-wise since it returns
  cached values.