Java 8中现已包含持续时间解析为纳秒再转换成毫秒

 PeriodFormatter formatter = new PeriodFormatterBuilder()
                .appendDays().appendSuffix("d ")
                .appendHours().appendSuffix("h ")
                .appendMinutes().appendSuffix("min")
                .toFormatter();

        Period p = formatter.parsePeriod("2d 5h 30min");
        Duration d = Duration.parse(p.toString());
        long milliseconds = d.toMillis();
        System.out.println(d);
        System.out.println(milliseconds);