question: public static Stats createAndMergeFrom ( Stats model ) { Stats r = new Stats ( model . name , model . unit , 0 ) ; r . histogram = new int [ model . histogram . length ] ; System . arraycopy ( model . histogram , 0 , r . histogram , 0 , model . histogram . length ) ; r . counts = new long [ model . histogram . length ] ; r . merge ( model ) ; return r ; }
target:  Use this method to merge this stat instance into a prototype one (for thread safe read only snapshoting)