With the Timer class, you can have a TimerTask that runs for a long time, blocking other tasks from running.
借助timer类，您可以拥有一个长时间运行的TimerTask，阻止其他任务运行。
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As such, they're tuned for a relatively small number of cores (two to eight) running coarser grained, possibly blocking transactional tasks that have few inter-task dependencies.