While a servlet holds a persistent request in a waitingstate, that servlet is monopolizing a thread.
当等待状态的servlet持有一个持久性请求时，该servlet会独占一个线程。
2
In the infinite loop case above, all threads except main are in a waitingstate (on a semaphore, or waiting for some event).
在上述死循环的情况下，所有除主线程之外的线程都处于某种等待状态(等待一个信号量，或等待某个事件)。
3
When the switch is closed, the variable pump has no oil supply, the current decline will keep the motor in empty waitingstate, thus effectively save energy.