One thing others haven't mentioned, you still have the option of creating a normal java object and manipulating it with the standard method accesses. Those are

One thing others haven't mentioned, you still have the option of creating a normal java object and manipulating it with the standard method accesses. Those aren't forced to be immutable by Clojure. Fortunately doing that makes it fairly obvious what you're doing since it won't look like seq accesses, creating a code smell so you can decide if you're doing it too much as you get better with the language.