@Test
    public void t10() {
        log.info("{}", R.UU16());
        log.info("{}", R.UU32());
        log.info("{}", R.UU64());
    }

2017-09-05 14:41:24.102  INFO   --- [           main] sunyu.example.OtherTests                 : 319da4960ca04fe3a8c081fd6c58a7c7
2017-09-05 14:41:24.103  INFO   --- [           main] sunyu.example.OtherTests                 : 2t5h6ur1ckhlbqk3pogfm41hm9
2017-09-05 14:41:24.103  INFO   --- [           main] sunyu.example.OtherTests                 : XasuB5RFGiXR6YQqinYXO2

打算用UU64了。集群环境，并发的，不会重复吧？