SKB – Scala abstract class


This article is part of the Scala knowledge bits Series.

Periodically, I will publish new exercises so you can slowly build up knowledge about Scala.

It is designed to be done in a very short amount of time and learn a little bit each day, just to create a routine.

This episode will teach you about Scala abstract class.

Hope you are going to enjoy it! It is designed for anyone to learn Scala from scratch and slowly learn, one Bit at a time.

After this Bit, I would love to hear your feedback in the comments down below.

Feel free to join the Discord server as well if you would like some help and support from the rest of our community.

What are we learning today?

Today we are going to learn about Scala abstract class !

This SKB is going to continue our progress in the Object Oriented Programming aspect of Scala.

abstract class are pretty similar to trait we saw before. But there are some slight differences.

Time to try on the exercise on your own and scroll down for more information when you are done or if you are stuck.


Here is an exercise to complete today.

If I did my job well, you should be able to guess by yourself the solution based on what you previously learned and based on the clues.

But if you get stuck, scroll down to get more information.

The goal of the exercise is to replace the ??? by a piece of code so that the exercise compiles and that’s how you win! Good luck!

You can fill the exercise right in here:

Or, if it does not load, go on to Scastie (fwuSQ1sSRhC5rURpo5vdvw).

More information about Scala abstract class

In this exercise you will learn (or have learned, if you have already solved the puzzle) about Scala abstract class.

You recognize the same keywords we learned about when we learned about trait. You can see extends, protected and override.

There are more differences but for the moment let’s go one step at a time.

The main difference you can notice compare to trait is that you are able to have a constructor directly when you extends the abstract class. This is pretty convenient to build simple pattern. We are going to see more about this in the context of enumeration.

To practice the concepts of Object Oriented Programming, Try to access the fields of Shape in the child classes. You notice that only lengthOfSides is protected and not the other ones. Remember class ? By default fields are private in a class. Try to add methods, maybe the area ?

Feel free to go back to the exercise, modify the code to try out new things and get a better intuition for Scala abstract class.


I hope you have learned something new or had fun during this Scala Knowledge Bit.

Please ask questions or post feedback in the comments below.

Feel free to try on the next Scala Knowledege Bit.

If you are curious about the previous Scala knowledge Bits, go check it out! 🙂

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