Yes, final is only 'shallow immutability' and only ensures that the reference itself is immutable. This is the only part that applies to closures though: the re

Yes, final is only 'shallow immutability' and only ensures that the reference itself is immutable. This is the only part that applies to closures though: the reference that is accessible from the closure. Full immutability is left up to the programmer / api designer as with javascript - as it should be, imo. Trying to optimize fully immutable data-structures when performance becomes an issue in an inner loop down the line is a nightmare I would not recommend.