$8\mathrm{.}22$ LAB: Timeout manager with PriorityQueue

Timeout manager overview

A timeout manager stores a priority queue of timeout items, each a $($callback method, callback time$)$ pair. Ea method is called approximately $N$ milliseconds after the timeout is set, where $N$ is the delay specified when a timeout item. Ex:

At time $t=0,$ a $500$ millisecond timeout is set for method $A$

At time $t=100,$ a $3000$ millisecond timeout is set for method B

At time $t=2000,$ a $1000$ millisecond timeout i$$ set for method C

So the timeout manager should call the callbacks as follows:

Call method A at time $t=0+500=500$

Call method C at time $t=2000+1000=3000$

Call method B at time $t=100+3000=3100$

A timeout item with a callback time $$ the current time is said to be "expired".

Millisecond$-$level callback precision is often unfeasible. So a timeout manager typically has an update methor by external code every so often, ex: every $100$ milliseconds. The manager's update method calls each expired callback method.

Step $1$: Inspect Timeoutltem.java

Inspect the Timeoutltem class declaration in the read only Timeoutltem.java file. Access Timeoutltem.java b$)$ orange arrow next to LabProgram.java at the top of the coding window. The callbackTime private field stol item was added plus the item's delay. Ex: A Timeoutltem created at $t=500$ with a delay of $1000$ has callbackTi $1000=1500.$ The callbackMethod private field is the method to call after the timeout expires.