I have created a class CoffeeMachine representing the coffee machine.
It has a property Map<String, Integer> ingredientContainer representing the state of ingredients inside the coffee machine
It also has a thread pool executor ExecutorService executorService. This thread pool executor handles the workers that will be submitted to dispense beverage.
Each worker can independently check the state of ingredients anytime. But while performing update (Collecting Ingredients) the workers have to acquire a lock. During this process no other thread can update or read the state of ingredients.
This lock is implemented using property ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock()
The class also has a method getBeverage that takes the order and abstract all internal working
The internal working to dispense beverage is handled by method dispenseBeverage.
I have also added a 2 seconds delay simulating actual coffee being made after ingredients are collected.
There are 2 more threads Thread indicatorService and Thread refillService.
The indicator service continuously reads the state of Coffee Machine and writes whether a particular ingredient is running low. It logs the details in resources/indicators.txt.
The refill service continuously checks a file resources/refill.txt if it contains any entry in following format: <ingredientName>:<amount>, the service tries to refill the given amount.
I have assumed the initial values of ingredient are the maximum capacity of the container. These are stored in Map<String, Integer> containerSizes while creating the initial state of the machine.
Execution
I have used one external library jackson:2.2.3 to parse the json file
We need to compile the source code using below command
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