[puredanger]

Having done substantial work in both Java and Clojure, my experience with abstraction in both is that in Java, making things more abstract almost always involves making the code larger (adding more interfaces, extending existing types to those interfaces, etc) whereas in Clojure making things more abstract typically means they get smaller.

Over time and at scale, this matters quite a lot. Java code grows and grows at a super linear rate as it handles new and changing requirements. This is ultimately not sustainable. Clojure code typically grows at a more linear rate (accretion of attributes in data or operations on data), but has more tools to create abstraction that can actually (if wielded well), be sub linear instead. This kind of change is not free or easy in any language, but in Clojure it is at least possible.