The classes LongStored and DoubleStored are not accessible outside the package org.openjdk.jmc.common.unit. The reason for this is that these are inner static classes of ScalarQuantity which is has only package-private visibility. Trying to access these classes leads to a compile error:
org.openjdk.jmc.common.unit.ScalarQuantity.LongStored is defined in an inaccessible class or interface
A fix would be to make ScalarQuantity public.
I'd like to access the LongStored and DoubleStored classes in order to find out if the underlying value of an attribute is a long or a double with an instanceof check.