public static <T> Collector<T, ?, Optional<T>> percentile(double percentile, Comparator<? super T> comparator) {
        return percentile(percentile, t -> t, comparator);
    }
Get a {@link Collector} that calculates the <code>PERCENTILE_DISC(percentile)</code> function given a specific ordering.
jOOL/src/main/java/org/jooq/lambda/Agg.java