question: public static String join ( List < ? > things , String delim ) { StringBuilder builder = new StringBuilder ( ) ; boolean first = true ; for ( Object thing : things ) { if ( first ) { first = false ; } else { builder . append ( delim ) ; } builder . append ( thing . toString ( ) ) ; } return builder . toString ( ) ; }
target:  Returns a list joined together by the provided delimiter, for example, ["a", "b", "c"] could be joined into "a,b,c"