Project requires maven and Java8.
To compile, run the following in the main project directory:
mvn compile
To run unit tests:
mvn test
To run the interactive console:
mvn package java -jar target/OracleTest-1.0.jar
The API is specified by the VendingMachineChangeAPI interface, and provides the following endpoints:
void setup(Map<Coin, Integer> initialFloat) throws InvalidCurrencyException
Setup the vending machine with an initial float of value initialFloat, provided as a map of coin type to counts of each type
in the initial float.
Throws an InvalidCurrencyException if any value is negative.
void deposit(Coin coin);
Deposit a coin into the vending machine; adding the coin to the float.
- Assuming that checking of the coins being valid (not zero or negative) is done elsewhere by the vending machine, this may or may not be worth checking here too depending on the reliability of the API user
Map<Coin, Integer> returnChange(Double changeValue) throws NotEnoughChangeException, InvalidCurrencyException;
Calculate the change to return to the user that sums to the changeValue, returns a map of coin type to counts of coin type.
Throws a NotEnoughChangeException if the total cannot be made with the current coins, or an InvalidCurrencyException if the
total is not positive.
- If performance was an issue, throwing an exception might be inappropriate for the case of not enough change, since it may be a common operation and throwing exceptions is much slower than returning a value. However, I thought it was a clearer way of indicating the error.
- Could have used
Doubles for coins but think that theCoininterface makes it clearer - Could have also used something like an
Enumfor coins, but this restricts to one set of coins, but would help ensure correctness. Current implementation allows for VendingMachines outside the UK market in the future easily. - Could have used something like a list of coins rather than a Map. I think that a Map probably works best for what the hardware would have: storing some number of coins of each type, but it might be harder to interface with a lower level language as it is a higher-level datatype.
- Used
InvalidCurrencyExceptions for negative and zero numbers. I think this is nicer as it makes it clear why it is not allowed, but perhaps one of the native java exceptions would have been better. - Decided not to provide methods for bulk actions such as accepting a list of coins deposited, as I thought it was unlikely that the vending machine would need this and it would add to the code base that requires managing. However, it would not be an easy addition in future if the requirement arose.
- Unsure exactly what was meant by an interactive test harness, so built the simple console application that can be seen when running the jar, along with unit tests as I was developing
- Tried to keep the API limited to tracking change as was specified, rather than, for example, making sure the user had deposited enough coins to accept the item after change was requested