Between ~1.5 hour up to ~4 hours,
depending on your previous experience & development environment.

Weather

In weather.csv you’ll find the daily weather data of a single month. Read the file, then output the day number (column one Day) of the day with the smallest temperature spread (difference between maximum & minimum temperature of the day.) The maximum temperature is the second column MxT, the minimum temperature the third column MnT.

Countries

countries.csv contains a list of data about the 27 countries of the European Union. Use the columns Population and Area to compute each country’s population density. Read the file, then print the name of the country with the highest number of people per square kilometre.

Task

1. Write a single program which is able to solve the "Weather" challenge.

2. Then refactor and extend your solution such that it additionally supports the Countries challenge.

Process

• Favour the software design goals described under Goal over other goals like performance or feature set.

• Include unit tests to ensure the correctness of your implementation.

Your solution should focus on maintainability, reusability and readability. Here are some hints on how you may achieve these goals:

1. The most important aspect is separation of concerns. Think about the different concerns involved in the task and how they may need to change in the future. For example: one concern is reading the file. What others components can you think of? Try to design separate, concise software components for each concern.

2. Often a quick diagram illustrating the components and their interactions can be helpful. If you draw a diagram, feel free to include it in your solution.

3. Design intuitive interfaces for the components in a way that each component can be replaced. For example in the next evolution step of your solution you might need to support other data formats like JSON files or even Web services. The Reader for the CSV-files in your example could be replaced with a reader that implements the same interface but reads JSON-files.

4. Use meaningful names for classes, properties and methods. By reading the name, one should already have an idea of what something does.

5. Think about possible error cases, e.g. if a file is empty or contains invalid input, and how they should be handled. Use log messages where necessary.

6. You may use additional third-party dependencies as you see fit. Please include your reasoning for your choice of libraries in your solution.

For this project, the Java Development Kit 11 or above is required. You can download it from https://adoptium.net/.

The starting point for every challenge is provided as a branch in a GitHub hosted Git repository. Be careful to adjust the URLs below accordingly.

To start

or if you’ve forked the repository then

The project scaffolds provides a Maven pom.xml as starting point. You should be able to start with any IDE or text editor you are convenient with.

After installing Maven 3.x or by calling the included Maven wrapper (mvnw and mvnw.cmd, depending on your operating system) you should be able to

Build & test your project

mvn verify

Then to run the main class de.bcxp.challenge.App

mvn exec:java

To remove the compilation output

mvn clean

Or use your IDE functionality

to run & debug your program.