public class RsLangs
extends Object
A set of languages, each represented by a canonical string object
The set is stored without any subsumed elements
Instances of this class are shareable
Duplicate-on-update strategy
Requires that all update operations to it return the
possibly new RsLangs object, and that calls are always of the form
rsLangInstance = rsLangInstance.[some-update-operation]
Requires that all copy operations set the shared bit:
copiedInstance = origInstance.setShared();
A instance marked isShared == true is immutable
Updates cause duplication.
Users store x-unspecified as null for the rsLangs instance
Because of this, users use static methods, passing in as the first argument,
the value of rsLangs, and getting an updated value of rsLangs.
This allows the passed-in value to be null.
Languages kept in canonical form:
duplicates removed
subsumed languages removed
language strings mapped to unique strings (allowing == comparisons)
Languages kept in array list, to allow for expansion
Languages not removed, only added (for a given tof)