Android连接RethinkDB-java.util.Optional

Question

Connection conn = r.connection().hostname("mywebsite.com").port(myport).db("mydbname").connect();

我得到了这个错误

FATAL EXCEPTION: Process: id.com., PID: 6957
                                                                java.lang.NoClassDefFoundError: java.util.Optional
                                                                    at com.rethinkdb.net.Connection$Builder.<init>(Connection.java:355)
                                                                    at com.rethinkdb.net.Connection.build(Connection.java:70)