Specification for
http://download.java.net/jdk8/docs/api/java/util/StringJoiner.html

in b89 (initial) spec contains the following example:

 * List<Person> people = ...
 * String commaSeparatedNames =
 * people.map(p -> p.getName()).into(new StringJoiner(", ")).toString();

there is no method Stream.into() currently so this code does not compile.