A super minimal implementation of a thread-pool-executor service / scheduler in Java. The goal is to provide a simple, easy to understand implementation. The implementation is not intended to be used in production, but rather to be used as a learning tool.
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There are 7 elevators in a building with 55 floors.
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Each floor has exactly one button to request an elevator.
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Elevators have the capacity of carrying an arbitrary, given number of people.
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Elevators don't change direction and don't stop mid-trip.
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People can only choose their destination freely, when they are on the ground-floor:
- up: ground-floor [0] − can only travel to ⟶ non-ground-floor [1;54]
- down: non-ground-floor [1;54] − can only travel to ⟶ ground-floor [0]
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The requests are handled globally.
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The elevator-scheduler assigns a chosen request to an elevator based on some arbitrary algorithm.
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If there are no elevators available, the request is queued up.
- Decided to use vanilla Java without any non-default libraries for the sake of simplicity.
- Got rid of the suggested "up"/"down" directions since they can be inferred from the current floor.
- Chose a poison-pill approach to terminate the scheduler (also see: this similar implementation)
- Chose JDK-19 to make use of type inferrence with
var
and other nifty features.