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Scala and Functional Programming, Why? By Mohammad Noor Abu Khleif

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Happy Saturday everyone! In this article Mohammad Noor Abu Khleif explains why his preferred functional language is Scala and explains a bit more about Scala.


"What is Scala?

“Scala combines object-oriented and functional programming in one concise, high-level language. Scala’s static types help avoid bugs in complex applications, and its JVM and JavaScript runtimes let you build high-performance systems with easy access to huge ecosystems of libraries”.

This is how Scala official website introduces the language to the world. In this blog, I will try to make this introduction some way simpler with a taste of real Scala examples, note that I’m assuming a general knowledge of other object-oriented languages like Java or C# but no functional programming knowledge is ok.


Scala is object-oriented

Scala is a pure object-oriented language in the sense that every value is an object. It’s even more object-oriented than Java, by that I mean that any value, even integers and doubles are objects! this opens a new world of no-special treatment for primitive values.


Scala is functional

Scala is also a functional language in the sense that every function is a value. That maybe sounds weird or even crazy, but it opens a whole new world and programming style/paradigm that Scala supports, which is the functional programming world. This is not a place to introduce functional programming style and benefits, but I will mention what help us here. Let’s back to the fact that every function is a value in Scala, that’s simply mean you can use a function anywhere you can use a value. Ummmm, a function?


A Method or a Function?

To be closer to understand what the functions are, we want to quickly compare them with methods. A method, in general, is a piece of code that does something and attached to a context, i.e, belongs to a class, while a function is simply a verb that does something or performs an action. In Scala, we can generalize (or converts) methods to functions, so we can use them outside the class they belong to!


Which is better?

The one should not treat OOP and FP as 2 worlds who should use one of them, even that’s possible in some cases, but to combine them both and use each of them when he/she needs to, and that’s exactly why Scala is found. In general, most of the programmers use OOP as the main paradigm and FP when they need to, which in most cases make the code simpler, shorter, and easier to understand and maintain.

Now, let’s start to discuss Scala,


Why Scala?

1. I will start with you, Java developers, because we share a lot together, we use the same base, yes, the JVM. That’s an incontestable point since JVM is mature enough, optimized enough, and have been in use for over than 15 years. You have a guaranteed very easy process to deploy and maintain applications, with a great performance!

2. The second point, which is that you have the best of both worlds! why should you use Java and stuck to OOP* or use Haskell and stuck to FP while you can get them together? Ok, I know that Java 8 introduced a lot of features to support FP, but that nothing compared to what Scala offers. May this seems to be a normal point for you but believe me, once you start to taste the FP, you cannot go back.

Let’s have a quick example, given a list of numbers, write a function/method that segregates even and odd numbers to 2 new lists.

Java Solution (Using Imperative Way):

import java.util.ArrayList;
import java.util.List;
public class MainJava {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
        List<List<Integer>> numberGroups = segregateNumbers(numbers);
        List<Integer> evenNumbers = numberGroups.get(0);
        List<Integer> oddNumbers = numberGroups.get(1);
    private static List<List<Integer>> segregateNumbers(List<Integer> numbers) {
        List<Integer> evenNumbers = new ArrayList<>();
        List<Integer> oddNumbers = new ArrayList<>();
        for (Integer number : numbers) {
            if (number % 2 == 0)
        ArrayList<List<Integer>> result = new ArrayList<>();
        return result;

Scala Solution (FP):

object MainScala extends App {
  val numberGroups = 0 to 10 partition (_ % 2 == 0)

3. That’s actually another point to mention for Java developers, Scala will give you more concise and short version of your code, let’s take another example of defining a simple class with basic methods in both languages:

Java Class:

import java.util.Objects;
public class JavaPerson {
    private final String name;
    private final String id;
    private int age;
    public JavaPerson(String name, String id, int age) { = name; = id;
        this.age = age;
    public String getName() {
        return name;
    public String getId() {
        return id;
    public int getAge() {
        return age;
    public void setAge(int age) {
        this.age = age;
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof JavaPerson)) return false;
        JavaPerson javaPerson = (JavaPerson) o;
        return age == javaPerson.age &&
                Objects.equals(name, &&
    public int hashCode() {
        return Objects.hash(name, id, age);
    public String toString() {
        return "JavaPerson{" +
                "name='" + name + '\'' +
                ", id='" + id + '\'' +
                ", age=" + age +

Scala Class:

case class ScalaPerson(name: String, id: String, var age: Int)

Yes, that’s it! and actually, the Scala class above explicitly contains even more methods than what I wrote on the equivalent Java one, how great is that?

4. Scala is a step ahead of Java, just think of lambda expressions on Java 8, and (limited) var and type inference on Java 10, and many other (new) Java features. They are in Scala since day 1, with much more use cases for them.

5. Scala is statically typed. It’s enough for Java, now let’s hit other languages, Python or Javascript? why those? because they are the most widely used dynamically typed languages. Wait, what is that mean? “Dynamically-typed languages perform type checking at runtime, while statically typed languages perform type checking at compile time. This means that scripts written in dynamically-typed languages (like Groovy) can compile even if they contain errors that will prevent the script from running properly (if at all). If a script is written in a statically-typed language (such as Java) contains errors, it will fail to compile until the errors have been fixed”[Oracle]. BTW, Groovy is another JVM language.

Let’s take this simple example in three languages, Python, JavaScript, and Scala:

Multiply 2 Numbers in Python:

def Multiply(num1, num2):
    answer = num1 * num2
    return answer

Multiply 2 Numbers in JavaScript (ES5):

var multiply = function(num1, num2){
    return num1 * num2;

Multiply 2 Numbers in Scala:

val multiply = (num1: Double, num2: Double) => num1 * num2

You see it, the ‘Double’ type, that’s mean that Scala will not compile at all if you call this function with non-numbers values! while this is OK for both Python and JavaScript, that’s maybe faster not to add that ‘Double’ type (is it?) but you lose a lot! you may compile this, release your product and there is 1 forbidden use in your code base that leads to huge bugs! so, keep your self safe and use a statically typed language.

6. Scala has type inference, that’s mean you still may not include the type of the value and let the Scala compiler infer it for you! just print val x = 5 and you are ready to go! there are rare cases where you have to declare the type yourself. so Scala is statically typed, and you can not write the type yourself, how amazing is Scala!

7. For Python users, a lot of you like the language to write quick scripts. And again, Scala can be used as a scripting language! did you read about REPL?

… Scala has a lot more to encourage you to choose it as your next journey."


Article originally posted on and written by Mohammad Noor Abu Khleif.