# SKB – Scala List Filter Method

## Introduction

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 List `filter` Method.

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 List `filter` Method !

In a previous SKB, we met the `map` method that the standard library offers. There are plenty more, but let’s focus on the `filter` method in this Scala Knowledge Bit.

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

## Exercise

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.

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 (EVfJS5WZRDWtIdzPHXOs6w).

## More information about Scala List `filter` Method

In this exercise you will learn (or have learned, if you have already solved the puzzle) about Scala List `filter` Method.

The `filter` method allows you to keep the elements of the list that return true for the test (Also called a lambda function).

For instance, for `list.filter(a => a > 2)`, the `list` will be filtered down to only keep the elements that are `> 2` (greater than 2). If the list was `List(1,2,3,4)` then the filter method would return a new list: `List(3,4)`.

Feel free to go back to the exercise, modify the code to try out new things and get a better intuition for Scala List `filter` Method.

## Conclusion

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

Feel free to try on the next Scala Knowledege Bit.

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

### 2 thoughts on “SKB – Scala List Filter Method”

1. I have one suggestion for this part:

If the list was containing List(1,2,3,4) then after the execution of the filter method, the list will only contain List(3,4).

This might confuse newcomers that filter method changes original list, in fact it return new list and leaves original untouched.

• That is very true !

I am going to edit the post to make it clearer. Thank you !