Best way to convert an ArrayList to a string

Answer 1

List stringList = getMyListOfStrings();
StringJoiner sj = new StringJoiner(" ");
stringList.stream().forEach(e -> sj.add(e));
String spaceSeparated = sj.toString()

You pass to the new StringJoiner the char sequence you want to be used as separator. If you want to do a CSV: new StringJoiner(", ");