code: protected long delayNanos(long currentTimeNanos) {
          ScheduledFutureTask<?> scheduledTask = peekScheduledTask();
          if (scheduledTask == null) {
              return SCHEDULE_PURGE_INTERVAL;
          }
  
          return scheduledTask.delayNanos(currentTimeNanos);
      }
docs: Returns the amount of time left until the scheduled task with the closest dead line is executed.