question: public final String matchCategories ( Set < String > categories ) { if ( categories == null ) { return null ; } Iterator < String > it = categories . iterator ( ) ; if ( mCategories == null ) { return it . hasNext ( ) ? it . next ( ) : null ; } while ( it . hasNext ( ) ) { final String category = it . next ( ) ; if ( ! mCategories . contains ( category ) ) { return category ; } } return null ; }
target:  Match this filter against an Intent's categories.  Each category in the Intent must be specified by the filter; if any are not in the filter, the match fails.