==WaitUntil{{c|waitUntil()}}==

Alarm has a new instance variable, {{c|waitingThreads}}, which is a Java {{c|PriorityQueue }} of waiting threads with the target wake time as their priority. It also contains a new inner class named waitingThread{{c|WaitingThread}}, which contains a reference to a {{c|KThread }} and its associated {{c|wakeTime}}. The {{c|PriorityQueue waitingThreads }} will be populated with instances of this inner class.

* {{c|waitUntil() }} creates a new instance of {{c|waitingThread}}, which will associate the currentThread current thread with the give given time argument. It will then add this {{c|waitingThread }} instance to the {{c|PriorityQueue }} and put the current thread to sleep. This method is atomic. * {{c|timerInterrupt() peek }} peeks at the first {{c|WaitingThread }} in the {{c|waitQueue }} and check checks if its associated wake time is less than or equal to the current time. If it is, this method will pop the {{c|WaitingThread }} off the {{c|waitQueue }} and wake the associated thread. This process is repeated until the wake time of the first {{c|WaitingThread }} is greater than the current time.

* Have the timer interrupt print a debug statement, and have timed threads print the times they go to sleep and when they have woken up. Verify that they wake up relatively close to their expected exit wake time.