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What is Kotlin?

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Without programming languages, the world of technology and innovation would cease to exist. Kotlin, like other programming languages, is the building block of curation of the software. The article is curated after significant research of the programming language, which provides a holistic view of Kotlin.

Readers will cover the cutting-edge features that distinguish Kotlin from Java, safety features, coroutines, the use of Kotlin in curating Android applications, and lastly, how beginners can run the first-ever Kotlin program.

Kotlin offers a comprehensive take on writing programming languages by reducing the overall spent time and maintaining a similar code for a unique platform. Given that the programming language is relatively new, the programming language is perfect for multiplatform applications. As more and more developers are getting into creating applications for Android rather than relying on Java.

Let’s explore the concise, safe programming language, which is still fun to write and read.  In the blog, What is Kotlin cover the real essence of Kotlin and its avenue to aiding organizations in the foreseeable future?

What is Kotlin - Table of Contents

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What is Kotlin Used For?

  • Kotlin  is a free, general-purpose, open-source, pragmatic, and statically typed programming language curated specifically for Java Virtual Machine or JVM and Android OS. Kotlin combines the functionalities of programming features and object orientation. Kotlin also focuses on safety, interoperability, tooling support, and clarity. There are distinctive versions of Kotlin which target LLVM, the native code, and JavaScript ES5.1 for several processors which are in production.
  • Kotlin came into being in 2010 by JetBrains. By the looks of it, JetBrains is the company behind the groundbreaking Integrated Development Environment, IntelliJ IDEA. Kotlin garnered the status of being an open-source in 2012. The company revealed that Kotlin features a team that has over 90 members from helming from JetBrains. In addition to this, Kotlin on GitHub features over 300 contributors. Most of the products from JetBrains use Kotlin, such as the flagship product, IntelliJ IDEA.

Let’s dive deeper to know Kotlin, inside and out!

Kotlin, a streamlined Java language

  • Suppose a developer who hasn’t heard or seen Kotlin even takes a look at the programming language. In that case, they will immediately find Kotlin to feature Java in the most streamlined and concise manner. If you take a look at the figure below, you’ll find out that the language doesn’t feature a mindless repetition to exemplify the Java variables, which are already gone.
  • The Java idiom StringBuilder sb = new StringBuilder() in Kotlin converts into val sb = StringBuilder(). Here, the functions are further defined in terms of the “Fun” keyword alongside semicolons which becomes optional in newlines. On the other hand, the “Val” keyword also declares a local variable or read-only property. Likewise, the keyword “Var” turns either into a local variable or a mutable property.
  • Kotlin is undoubtedly a very strongly typed programming language. The keywords “Var” and “Val” can only be used when the type could be inferred. Else you’ll have to declare the class where the type inference would improve with the release of each Kotlin.

If you take a closer look at the figure near the function declaration on the top of the panes. The return type of Java will precede the whole prototype. Things are a little different in Kotlin as it does succeed in terms of the prototype, which is further demarcated in Pascal. Kotlin did relax the whole of Java’s requirement, which functions like class members. Functions in Kotlin can be found in the top-most file-level and locally in distinctive parts. Extension functions also provide a C# kind of ability that extends the class with a completely new functionality irrespective of inheriting a class or design pattern.

Kotlin also became famous for implementing builders; moreover, Kotlin builders could comprise of being type-checked. The languages offer support for authorizing properties which further implements observable, lazy, mapped, vetoable properties.

Asynchronous machines of other programming languages could witness implementation as libraries use the coroutines of Kotlin. Some of these machines are async/await from ECMAScript and C#, channels, go, and generators/yield from Python and C#.

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Kotlin Features

Kotlin has become increasingly popular due to its unique features. Let’s get into the numerous features that Kotlin has to offer:

  1. Interoperability: As a programming language, Kotlin is very much compatible with Java. Developers are not going to face any difficulty while using the language in any Java project.
  2. Easy: Learning Kotlin is very seamless. As the programming language is built from Java, learning Kotlin is very easy.
  3. Concise: The programming language is essentially more incisive than Java. This would further require you to write 40% fewer lines of code than Java. Given the Kotlin draws inspiration from Java, it offers more of a practical approach.
  4. Feature-rich: The programming language comes with numerous cutting-edge features like Lambda Expressions, Operator Overloading, String Templates, among others.
  5. Less error-prone: Basically, Kotlin is a holistic statically-typed language that ensures the developers catch errors during compile-time. It shares many traits with other statically-typed programming languages which are in existence.

Kotlin Functional Programming

In functional programming, the top-level functions are kept in the beginning. Kotlin supports anonymous functions, higher-order functions, closures, inline functions, generics, and tail recursion. In simple terms, Kotlin comprises all features alongside the advantages which constitute functional language. Check out the valuable idioms of Kotlin below:

1. Filtering a list in Kotlin

If a developer wants to add shorter expressions, then he can use the following command:


al positives = list.filter { x -> x > 0 }

Remember, developers can use this only when there is a single-most parameter in terms of the lambda function, like this:

Val positives = list.filter { it > 0 }

2. Traversing a map/pairing list in Kotlin

Traversing maps or lists of pairs would require for 

((k, v) in map) { println(“$k -> $v”) }

Here developers can call K and V into anything.

Use of ranges in Kotlin

The notable example of the use of ranges and “for” keyword is:

for (i in 1..100) { ... }  // closed range: includes 100

for (i in 1 until 100) { ... } // half-open range: does not include 100

for (x in 2..10 step 2) { ... }

for (x in 10 downTo 1) { ... }

if (x in 1..10) { ... }
  • Kotlin is a proficient and functional computer programming language that preserves the innate nature of being object-oriented in Java. Kotlin is also considered an alternative to a programming style that is extremely handy for developers while converting the Java code, which is already in existence.
  • Moreover, Kotlin comes with classes alongside constructors, anonymous inner, inner, and nested classes. The programming has a similar interface, just like Java 8. Remember, Kotlin doesn't come with a brand new keyword. Creating a class instance initiates a constructor's calling, which isn't different from a regular function.
  • Kotlin comes with single-most inheritance from any named superclass. The default superclass in Kotlin is "Any", which comprises three predetermined functions such as hashCode(), equals(), and toString(). Kotlin doesn't share any form of similarity with java. lang.Object.Any.
  • In Kotlin, classes are required to mark with the "open" keyword to allow different classes to be inherited. Java classes are a little other from Kotlin as they inherit the "final" keyword. Ov
  • overriding any superclass method would require to mark open, whereas subclass is used to keep override. These constitute Kotlin's philosophy to make things concise by being independent of defaults.

Safety Features

  • Kotlin comes with safety features that speak of avoiding some of the common errors. The programming language came into being to eliminate the overall danger that null pointer references had. It further streamlines null values handling. The only way Kotlin facilitates null values is by making "null" illegal, implementing notations, and adding different types of nullable.

String type regular variable can hold the null in this manner:

var a: String = "abc"
a = null // compilation error

If nulls are allowed to hold query results in SQL, then you can easily declare a question mark depicting a null, e.g., “String?”

var b: String? ="abc"

b = null // ok

As far as the protections are concerned, developers can utilize non-nullable immunity. However, you’ll also have to test nulls right before using it.

It is essential to avoid wordy grammar during null testing. The programming language comes with a feature called safe call, which functions in this manner: ‘b'?.length’ that returns to ‘b.length’ only if ‘b’ isn’t null. The expression is called ‘Int?.’

b?.length is the shortcut of

“if (b != null) b.length else null”, 

The syntax here chains up appropriately by eliminating a massive amount of prolix logic, especially at times when an object attains population from a series of database queries.

There is a specific action for non-null values that can be performed by using a safe call operator, i.e., ‘?'. alongside ‘let:’. Check out the following code:

val listWithNulls: List<String?> = listOf("A", null)

for (item in listWithNulls) {

  	item?.let { println(it) } // prints A and ignores null }

Developers often opt for a remarkable value return directly from nullable expressions. The action allows saving the value into non-nullable segments. Also, there is an exceptional syntax called Elvis operator, which is written as 

val l = b?.length ?: -1

Furthermore, the Elvis operator is equivalent to 

Val l: Int = if (b != null) b.length else -1.

This suggests that Kotlin omits the checked exceptions of Java which are found in the throwable condition. JDK signature is one such example of checked exceptions of Java.

Appendable append(CharSequence csq) throws IOException;

It requires developers to catch the IOException each time they call up to append method, in this manner:

try {



catch (IOException e) {

  // Do something with the exception


Initially, the Java designers thought this to be a great idea. The idea was a decisive win for the toy programs as long as programmers implement any sensibility alongside the catch clause. In massive Java programs, developers often see codes that are a compulsory catch clause featuring only a single comment, i.e., //todo: handle this. Sadly, the command didn’t seem to help anyone, and the exceptions did become a complete loss for more extensive programs.

Learn Kotlin Interview Questions and Answers that help you grab high-paying jobs


These are the lightweight threads in Kotlin. They can be started using this coroutine builder: ‘launch’ in the context of CoroutineScope. Additionally, runBlocking{} is regarded as a very useful coroutine that can be put into the code block.

import kotlinx. coroutines.*
fun main() = runBlocking { // this: CoroutineScope

	launch { // launch a new coroutine in the scope of runBlocking

    	delay(1000L) // non-blocking delay for 1 second





The code helps in producing this output:


World! (Note that there will be a one-second delay between both lines)

Kotlin for Android

  • Till May 2017, the programming languages were the only programming languages that supported Android OS were C++ and Java. During the official Google I/O, the streaming giant announced that Android would support Kotlin. Ever since Google came up with Android Studio 3.0, Kotlin has been built into Android OS's development toolset. Kotlin then brought support for the earlier versions of the Android Studio alongside a plug-in.
  • Kotlin shares a similar byte code just like Java, allowing the integration of Java classes in the most natural manner. Additionally, Kotlin also shares tooling with Java. It is a sensible decision to add Kotlin gradually to any Android application as it makes perfect sense. There are a few cases where standardization among Java and Kotlin code lacks grace.
  • One of the notable examples of an app made using Kotlin is Pinterest. The image-sharing platform came into being in November 2016. In 2017 Google I/O, the search giant unveiled the application Pinterest. Additionally, the team also cited some essential applications like Trello, Evernote, Coursera, and Square, which are made using Kotlin.

Kotlin vs Java

  • Developers often go through a dilemma when choosing between Java or Kotlin for developing new apps in the ever-growing Android community. Even when Kotlin 1.0 was released, developers kept asking how Kotlin would offer things differently from Java. Most concisely, the answer is Kotlin provides better safety, and it is increasingly more concise than Java code. Both Java and Kotlin could coexist inside of an Android application. Kotlin is not helpful for the new apps, but it also expands to the existing ones.
  • Java is the best programming language for beginners, mainly the ones who are new to the Android ecosystem. However, it is easier to convert Java into Kotlin using Android Studio. So, there is no need to put Java against Kotlin as both serve the same purpose.
  • However, Kotlin offers exciting android development. An android developer can learn the basics of Kotlin in a few hours. Kotlin offers 40% less time in writing the code as compared to Java.
  • Running the first Kotlin program
  • Before you learn how to get around curating the first-ever Kotlin program, developers will be required to install Intellij IDEA, preferably the latest version. In 2021, Kotlin comes with recent iterations of Intellij. Here, you’re not going to need an additional plug-in for running Kotlin programs.

[ Related Article: Comparision between Kotlin and Java ]

Here are the steps if you want to create an all-new Kotlin project using IntelliJ:

Step 1:

Choose ‘Create New Project’, which you notice on the welcome screen. You can also follow this order: File → New → Project. Now choose Kotlin, located on the left-hand side of the menu.

Step 2:

Specifically, put forward the name of the project as well as the location. Now, you’ll have to select the Java version present in the Project SDK. The moment all details are entered. Choose to click on Finish, and now the project will be created. The project will look something like this:

Step 3:

Now, you’ll be required to create a new Kotlin file, so make a right-click on the src folder → New → Kotlin File/Class. A new prompt will pop up where developers will have to provide a name specifically for a file.

Step 4:

 Follow the step of writing a simple Kotlin program like the one in the figure below.

Writing the program involves I and III line functions:





fun main (args: Array <String>)


println("Welcome to Kotlin Language")


In the first line, Functions serve as the building blocks of the Kotlin program. Functions in Kotlin begin with this keyword- ‘fun’. It follows a name alongside a list of several zeros and parameters separated by common. Developers can also find that the image and the command include the return type, body, taking one argument, and turning it into an array of things.

The third line displays the output message on the screen. Developers can also use println() if they wish to print out the standard code.


Since its inception, Kotlin did gain a lot of traction from developers from across the world. As the programming language is expressive, concise, and safe, it is a worthy competitor of JAVA and its replacement. As per Google, Kotlin has become the official Android development programming language. Kotlin is in for the long haul. If a developer is already aware of the avenues that Kotlin can fathom, then learning the programming language won’t just boost your career. Instead, it will change your entire perspective on Android app development while increasing productivity.

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As a content writer and storyteller, Raunaak Mitra regards himself to be a prodigy in writing. He firmly believes that language is borderless, and anyone can write as long as they have a strong narrative capability and the ability to emote feelings into words. Authors like F. Scott Fitzgerald and R. K. Narayan have influenced him to keep the writing as simple as possible for anyone to understand. Other than being well-versed about technological trends like AI, Machine Learning, AR, VR, Gaming, Microprocessors, Cloud Computing, Industry 4.0, literally any technological advancement (old or new), he also shares a knack to curate fiction on sci-fi, satire, and thriller genres.

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