code: public Class<? extends MonetaryAmount> getAmountType() {
          Class<?> clazz = get(AMOUNT_TYPE, Class.class);
          return clazz.asSubclass(MonetaryAmount.class);
      }
docs: Get the MonetaryAmount implementation class.
  
  @return the implementation class of the containing amount instance, never null.
  @see MonetaryAmount#getContext()