Developer Programming Exercise

User Story

As a trader I want to be able to monitor stock prices such that when they breach a trigger level orders can be executed automatically.

Exercise

Given the following interface definitions (provided)

public interface ExecutionService {
    void buy(String security, double price, int volume);
    void sell(String security, double price, int volume);
}

public interface PriceListener {
    void priceUpdate(String security, double price);
}

public interface PriceSource {
    void addPriceListener(PriceListener listener);
    void removePriceListener(PriceListener listener);
}

Develop a basic implementation of the PriceListener interface that provides the following behaviour:

1. Connects to a PriceSource instance
2. Monitors price movements on a specified single stock (e.g. "IBM")
3. Executes a single "buy" instruction for a specified number of lots (e.g. 100) as soon as the price of that stock is seen to be below a specified price (e.g. 55.0). Don’t worry what units that is in.

Considerations

• Please "work out loud" and ask questions
• This is not a test of your API knowledge so feel free to check the web as reference
• There is no specific solution we are looking for

Some libraries already available:

• Java 8
• JUnit 4
• Mockito
• EasyMock
• JMock