code: public static DocumentBuilderFactory newInstance(String factoryClassName,
              ClassLoader classLoader) {
          if (factoryClassName == null) {
              throw new FactoryConfigurationError("factoryClassName == null");
          }
          if (classLoader == null) {
              classLoader = Thread.currentThread().getContextClassLoader();
          }
          try {
              Class<?> type = classLoader != null
                      ? classLoader.loadClass(factoryClassName)
                      : Class.forName(factoryClassName);
              return (DocumentBuilderFactory) type.newInstance();
          } catch (ClassNotFoundException e) {
              throw new FactoryConfigurationError(e);
          } catch (InstantiationException e) {
              throw new FactoryConfigurationError(e);
          } catch (IllegalAccessException e) {
              throw new FactoryConfigurationError(e);
          }
      }
docs: Returns an instance of the named implementation of {@code DocumentBuilderFactory}.
  
  @throws FactoryConfigurationError if {@code factoryClassName} is not available or cannot be
  instantiated.
  @since 1.6