code: public static synchronized Schema getXJCLSchema() {
          if (schema == null) {
              try {
                  URL url = ValidatorHelper.class.getResource("/" + SCHEMA_LOCATION);
                  schema = sf.newSchema(url);
              } catch (SAXException e) {
                  throw new RuntimeException(e);
              }
          }
          return schema;        
      }
docs: This method must be synchronized as SchemaFactory is not thread-safe