question: public final int updateAndGet ( T obj , IntUnaryOperator updateFunction ) { int prev , next ; do { prev = get ( obj ) ; next = updateFunction . applyAsInt ( prev ) ; } while ( ! compareAndSet ( obj , prev , next ) ) ; return next ; }
target:  Atomically updates the field of the given object managed by this updater with the results of applying the given function, returning the updated value. The function should be side-effect-free, since it may be re-applied when attempted updates fail due to contention among threads.