src/org/nutz/lang/Tasks.java
public static void scheduleWithFixedDelay(final Runnable task, Date startTime, final long period, final TimeUnit unit) {
        final Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                taskScheduler.scheduleWithFixedDelay(task, 0, period, unit);
                timer.cancel();
                timerList.remove(timer);
            }
        }, startTime);
        timerList.add(timer);
    }
public static void scheduleWithFixedDelay(final Runnable task, Date startTime, final long period, final TimeUnit unit) {
        final Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                taskScheduler.scheduleWithFixedDelay(task, 0, period, unit);
                timer.cancel();
                timerList.remove(timer);
            }
        }, startTime);
        timerList.add(timer);
    }
在指定的时间点启动，两次任务间保持固定的时间间隔
@param task 具体待执行的任务
@param startTime 首次运行的时间点
@param period 两次任务的间隔时间
@param unit 时间单位