I am struggling how to perform basic operations using a Guava ImmutableSortedMultiset...
I don't think you can do it without rebuilding a new ImmutableSortedMultiset. Assuming you have an
original multiset, I would start by making a composite view using the methods in
// View with one more element Multiset<String> view = Multisets.union(original, ImmutableMultiset.of("a"));
// View with one less element Multiset<String> view = Multisets.difference(original, ImmutableMultiset.of("a"));
followed by creation of the immutable sorted copy:
ImmutableSortedMultiset<String> copy = ImmutableSortedMultiset.copyOf(view);