How to sort Iterable in ProcessWindowFunction?

[HG]

Hi,
I have need to sort the input of the ProcesWindowFunction by one of the
fields of the Tuple4 that is in the Iterator.

 static class MyProcessWindowFunction extends
ProcessWindowFunction<Tuple4<Long, Long, String, String>, String, String,
TimeWindow> {
        @Override
        public void process(String key, Context context,
Iterable<Tuple4<Long, Long, String, String>> input, Collector<String> out)
        {
            Long elapsed       = 0L;
            Long pHandlingTime = 0L;
            Long totalElapsed  = 0L

            System.out.println(input.getClass());

            Iterator<Tuple4<Long, Long, String, String>> etter =
input.iterator();
            *for (Tuple4<Long, Long, String, String> in: input){*
                transactionId = in.getField(2).toString();
                elapsed       = Long.parseLong(in.getField(1).toString()) -
pHandlingTime;
                totalElapsed  = totalElapsed + elapsed;
                pHandlingTime = Long.parseLong(in.getField(1).toString())

                out.collect("Key : " + key + " Window : " +
context.window() + "  transactionId : "  + transactionId + "  elapsed : " +
elapsed.toString() + "  max handling time : " + h.toString() + "
totalElapsed " + totalElapsed);
            }
        }
    }