code: public boolean isValueKnown() {
          Type type = getType();
          if (type != null) {
              Class<?> clazz = type.getObjectClass();
              return Number.class.isAssignableFrom(clazz) ||
                  clazz.isAssignableFrom(Number.class);
          }
          else {
              return false;
          }
      }
docs: Value is known only if type is a number or can be assigned a number.