question: public synchronized void cacheReposts ( List < Long > newRepostIds ) { TreeSet < Long > reposts = new TreeSet < > ( ) ; reposts . addAll ( Longs . asList ( repostCache . get ( ) ) ) ; reposts . addAll ( newRepostIds ) ; repostCache . set ( Longs . toArray ( reposts ) ) ; }
target:  Caches the given items as reposts.