Top 25 Kotlin’s Interview Questions and Answers in 2023

Kotlin is a popular Android programming language. Suppose you are looking for a career involving Kotlin programming. In that case, you should prepare to answer questions regarding your Kotlin skills and experience. This article provides solutions to some of the most typical Kotlin Android interview questions to help you prepare for your responses.

1. What Are The Essential Abilities A Mobile Developer Should Possess?

Communication and problem-solving are the two most essential talents for a smartphone developer. Communication is critical since it permits me to collaborate with other team members, share my ideas, and ask for assistance when necessary. Having good problem-solving abilities assists me in resolving any problematic issues that may occur during development. These abilities enable me to execute assignments on schedule and meet the client’s requirements.

2. How Familiar Are You With Using Android Studio?

I find Android Studio’s various features to be handy. I particularly appreciate using the emulator, which allows me to test my apps on many devices without purchasing them all. The code editor is particularly advantageous because it indicates problems as I type, allowing me to determine if something is not functioning correctly immediately. My only concern with Android Studio is that compilation occasionally takes longer than anticipated.

3. What Would You Do Differently Next Time If An Application You Created Was Unsuccessful?

In my previous position as a Kotlin developer, I created an application for a client whose need was that it be compatible with multiple devices. However, when I uploaded the application, the client stated that it did not function on their device. I discovered after conducting an investigation that I had neglected to add compatibility with one of the company’s operating systems. In the future, I will ensure that I test all operating systems before submitting a final product.

4. How Successfully Do You Communicate With Other Development Team Members?

I am proud of my communication abilities since they help me keep organized and guarantee that I always give my coworkers precise instructions. In my previous position, I collaborated closely with two other developers who were also new to the organization. We shared our progress and discussed any questions via Slack and email frequently. It meant we were all up-to-date on our projects and could execute our tasks efficiently.

5. Have You Previously Worked With Remote Teams?

I have worked on multiple projects where I was the sole developer, so I am accustomed to being my team’s primary point of contact. However, I also have expertise working with large, distantly located development teams. In such circumstances, I find that communication is crucial. I use platforms such as Slack and Jira to stay informed about the project’s status and provide comments as necessary.

6. Give An Example Of A Successful Kotlin Application You’Ve Created And Explain What Made It So.

Recently, I created an application for a customer who desired a mobile app that would enable users to place orders from their favorite eateries. The application required intuitive navigation, a menu of available food, and location details for each restaurant. I designed a user-friendly layout with a search function so clients could locate just what they desired. I also incorporated a loyalty program via which clients may earn points redeemable for discounts on future orders.

7. Are You Confident In Your Ability To Work Independently To Create New Applications Using Kotlin?

Yes, I am highly comfortable developing new Kotlin applications independently. Due to my skill in mobile application development, I was in charge in my previous position of developing new apps for clients. I appreciate working autonomously and utilizing my imagination to create one-of-a-kind customer solutions.

8. Describe Kotlin In Brief.

Kotlin is a general-purpose programming language that is open-source and statically typed. It operates on JVM and can be utilized in any setting where Java is now employed. It is possible to compile it using either Java source code or the LLVM compiler. It is typically utilized in the development of Android applications, as well as server-side apps and a great deal more. Kotlin, a programming language designed specifically for mobile applications, was given an official push by Google. Kotlin is now being evaluated as a potential replacement for the traditional Java compiler.

9. What Are The Main Characteristics Of Kotlin?

The most popular Kotlin features are:

  • Low Learning Curve: Due to its low cost of adoption, Kotlin is favored by many businesses. Most importantly, it is straightforward to learn for developers, especially those with programming experience.
  • Compilation Time: In terms of performance and compilation time, Kotlin is faster and superior to Java.
  • The programming language Kotlin is tools-friendly. Kotlin programs can be constructed using the command line or any Java IDE.
  • Kotlin is Concise: Kotlin decreases the extra code we must write, making it more concise.
  • Kotlin is an OOPs-based programming language that produces compact code. Its code lines are up to 40 percent less than Java’s, making it a good alternative for software development.
  • Kotlin is Simple: Kotlin is an easy-to-learn language. With Kotlin, code compilation is straightforward, enhancing Android programming performance. It also describes the data functions that we can use throughout the programming.
  • Kotlin is an open-source programming language for Android that uses the JVM to combine the advantages of OOPs and functional programming.

10. Why Do Most Software Engineers Prefer To Work In Kotlin Rather Than Java?

The programming language Kotlin appears to be easier and more organized than Java. Compared to Java, it eliminates numerous redundant code elements. Additionally, Kotlin offers specific critical capabilities that Java does not currently implement, making the code more idiomatic. Recently, Kotlin’s developers added it to Android Studio’s list of supported languages. Therefore, there is much to anticipate from Kotlin regarding lowering development efforts and future support.

11. What’s The Difference Between Open And Public Keywords In Kotlin?

The keyword “open” refers to “open for growth.” The open annotation on a class is the exact opposite of the final annotation in Java; it allows others to inherit from the course. In Kotlin, the code does not inherit types by default. An open method in Kotlin indicates that it can be overridden when by default, it cannot. Instead, all Java methods are overridable by default. By default, all classes in Kotlin are public. If no visibility modifier is present, the default is public, which makes our declarations available across the program.

12. Can You Define Higher-Order Functions And Explain Why They Are So Helpful?

Higher-order functions accept other functions as inputs and return another function. They are helpful because they enable you to find common abstract patterns and eliminate code duplication. You could, for instance, build a higher-order function that takes a predicate (a function that returns a Boolean) and applies it to a list to filter out the even integers. We might then reapply this higher-order function to other lists with distinct predicates.

13. What Exactly Are Data Classes? Are They Not Available In Java?

Occasionally, we utilize a class to hold data and nothing else. We refer to them as Data classes. These classes could be created using Java, but only with the explicit implementation of getter and setter methods for each property. Also, we may need to individually implement functions such as equals, toString, and copy. Kotlin natively implements all of them together with additional functions known as component functions. Eliminating superfluous code is an excellent practice.

14. Explain The Keyword “When” In The Context Of Kotlin.

Kotlin uses the “when” keyword to replace the switch operator seen in languages such as Java. When we fulfill a specific condition, we execute a particular code block. Each branch is compared individually within the when expression until it finds a match. When it finds the first match, it advances to the end of the when block and runs the code that follows the when block. Unlike switch cases in Java or any other programming language, we do not require a break statement at the end of each case.

15. What Is The Key Distinction Between Declaring Variables Using Var And Declaring Variables Using Val?

Both declare variables with var and variables with Val are utilized, although in distinct contexts and for different reasons. It would help if you used the var notation whenever you want to declare a variable that we can change. If you’re going to display a variable, we cannot alter it in any way; you should use the var keyword. We cannot modify the variables after they have been assigned.

16. What Is The Meaning Of Data Classes In Kotlin?

Data classes are classes that we design to store information. In Kotlin, we indicate them as data. The following illustration illustrates a data class: data class Developer (Val name: String, Val age: Int). When we designate a class as a data class, we are not required to implement or construct the following functions, as we must in Java: hashCode(), equals(), toString(), copy() (). The compiler generates these internally, which also results in clean code. However, there are a few more conditions that data classes must meet.

17. In Kotlin, What Is The Purpose Of @JvmStatic, @JvmOverloads, And @JvmFiled?

The primary uses of @JvmStatic, @JvmOverloads, and @JvmFiled in Kotlin include the following:

  • @JvmStatic: The @JvmStatic annotation informs the compiler that the method is static, and we can use it in Java code.
  • @JvmOverloads: When we pass default values as arguments from Java code to Kotlin code, the @JvmOverloads annotation is necessary.
  • @JvmField we use it to access the fields of a Kotlin class from Java code without using getters and setters. In the Kotlin code, we must use the @JvmField.

18. What Exactly Are Coroutines In Kotlin?

Kotlin, unlike many other programming languages with comparable features, lacks the async and await keywords in its standard library.JetBrains’ kotlinx. a coroutine is a comprehensive library for Kotlin coroutines. This library offers several high-level coroutine-enabled primitives, such as launch and async. Kotlin Coroutines provide an API for progressively writing asynchronous code.

According to the documentation for Kotlin, Coroutines are comparable to lightweight threads. They are lightweight because they do not allocate additional threads when we create them. They utilize specified thread pools and intelligent scheduling instead. Scheduling is determining the work in a sequential process and selecting the next task we want to perform. Coroutines can be suspended and resumed during execution. It allows us to have a long-running task that we can execute individually. We can halt it as often as possible and continue it as necessary.

19. What Exactly Is The Lateinit Keyword In Kotlin, And When Is It Used?

The term “lateinit” refers to a delayed startup. We use it in situations in which we do not want to initialize a variable in the constructor but would instead do it at a later time. Instead of utilizing the variable before declaring it with the latest keyword, which will guarantee the variable’s initialization, we should declare it first. We cannot use Lateinit for primitive type attributes such as Int, Long, or others.

20. What Are Some Of The Names Of The Extension Methods That Kotlin Makes Available To The Java.Io.File Class?

The following is a list of extension methods that Kotlin makes available to the File:

  • bufferedReader() is a function utilized in the process of reading the contents of a file into a BufferedReader.
  • readBytes() is the method we use to read the File’s contents into the ByteArray variable.
  • readText() is the function responsible for reading a file’s contents into a single String.
  • Kotlin programmers use the for each line() function to read one line from a given file at a time.
  • readLines() is the function responsible for reading lines from the File to the List variable.

21. When Compared To “Switch,” What Are The Benefits Of Using The “When” Keyword In Kotlin?

Java makes use of the “switch” keyword, whereas Kotlin changes “switch” to “when” for the same purpose. When it has a superior design compared to a “switch,” it is more concise and powerful than a conventional switch. When we want to make a remark or employ an expression, we might use the word “when.”

22. Explain Scope Functions In Kotlin’s Context. What Kinds Of Scope Functions Does Kotlin Support?

Various functions in the Kotlin standard library facilitate the execution of a block of code within the context of an object. When calling these functions, it produces a temporary scope using a lambda expression. These operations are known as Scope functions. It is possible to access the thing of these functions without knowing its name. Scope functions improve the clarity, readability, and conciseness of code, which are essential characteristics of the Kotlin programming language.

The following are the Scope functions supported by Kotlin:

  •  with:-‘with’ is preferred when invoking functions on context objects without passing the lambda result.
  • also:-We use it when we want to perform further operations after initializing the object members.
  • let:-We employ it for null safety calls. Use the safe call operator(?.) with let for null safety. It only executes the block if its value is non-null.
  • apply:-As the name says, “Apply these to the item,”.We use it to operate on the members of the receiving object, primarily to initialize them.

23. What Do You Understand By Kotlin Lazy Initialization?

Lazy initialization is a feature that is available in the Kotlin programming language. This feature states that your variable will not be initialized unless you utilize that variable in your writing code. Only one time will an initialization take place for it. After that, you continue to make use of the previous value.The lazy() function is used in lazy initialization. This function takes a lambda as an argument and returns an instance of lazy. An example of lazy can serve as a delegate for implementing a lazy property. The first call to get() executes the lambda passed to lazy() and remembers the result—subsequent calls to get() return the result.

24. What Types Of Modifiers Does The Kotlin Programming Language Offer?

The declarations can be made uniquely for each developer through modifiers. There are four different kinds of modifiers that we can use in Kotlin. They are as follows:

  • Public: All declarations are accessible to the public by default, regardless of location.
  • Internal: This modifier, used internally, makes it possible to utilize declarations anywhere within the module.
  • Private: Because of these modifiers, the declarations are only found in the file that has its access restricted.
  • Protected means that the declarations are safe and cannot be accessed by top-level declarations.

25. What Is The Difference Between Blocking And Suspending?

A blocking call to a function means that any subsequent function call from the same thread will halt the execution of the parent function. As a result, if you make a blocking call on the main thread’s performance, you effectively freeze the user interface. The user will observe a static display until the blocking calls conclude, which is undesirable.

In contrast, suspending does not necessarily halt the execution of your parent function. If you invoke a suspending function in one thread, you can quickly move it to another. Even if the process is intensive, it will not block the main thread. If the suspending function must suspend, its execution is halted. Thus, the thread is made available for other tasks. After pausing, it will obtain the following available thread from the pool to complete its function.


Kotlin is a flexible and robust language, but it also possesses several difficulties. There is always something new to learn, regardless of how long you have been using it. Before interviewing for your next Kotlin developer position, check this article’s Kotlin interview questions.

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