question: public boolean retainAll ( AbstractFloatList other ) { if ( other . size ( ) == 0 ) { if ( size == 0 ) return false ; setSize ( 0 ) ; return true ; } int limit = other . size ( ) - 1 ; int j = 0 ; for ( int i = 0 ; i < size ; i ++ ) { if ( other . indexOfFromTo ( getQuick ( i ) , 0 , limit ) >= 0 ) setQuick ( j ++ , getQuick ( i ) ) ; } boolean modified = ( j != size ) ; setSize ( j ) ; return modified ; }
target:  Retains (keeps) only the elements in the receiver that are contained in the specified other list. In other words, removes from the receiver all of its elements that are not contained in the specified other list. 