static < E > ImmutableMap < E , Integer > indexMap ( Collection < E > list ) { ImmutableMap . Builder < E , Integer > builder = new ImmutableMap . Builder <> ( list . size ( ) ) ; int i = 0 ; for ( E e : list ) { builder . put ( e , i ++ ) ; } return builder . build ( ) ; }
Returns a map from the ith element of list to i .