type instanceof Number.

 public static Type<?> getIdType(JavaClass<?> entity)
   {
      for (Member<?> member : entity.getMembers())
      {
         if (member.hasAnnotation(Id.class))
         {
            if (member instanceof Method)
            {
               return ((Method<?, ?>) member).getReturnType();
            }
            if (member instanceof Field)
            {
               return ((Field<?>) member).getType();
            }
         }
      }
      return null;
   }

    public static boolean isNumberIdType(JavaClass<?> entity)
   {
      return getIdType(entity) instanceof Number;
   }

   public static boolean isNumber(final String type)
   {
      if (isBasicType(type))
      {
         if (isPrimitive(type))
         {
            return Arrays.asList("int", "long", "float", "double", "short").contains(type);
         }
         return Arrays.asList("Boolean", "Byte", "Double", "Float", "Integer", "Long", "Short").contains(
                  type);
      }
      return false;
   }