Top Kotlin Interview Questions For Beginners


Hello everyone; in this article, we will discuss a few questions and their solutions that can be crucial in advancing your understanding of Kotlin programming. At first glance, the questions in this article appear straightforward, but as you read further, the difficulty level of the questions rises, and you become more intrigued by the challenge. Hence, attempt to tackle the issues before looking for solutions.

Q. Has kotlin implemented null safety?

Answer- Yes, Kotlin has implemented null safety features. Kotlin is designed to reduce the number of NullPointerExceptions (NPEs) in code, a common problem in languages like Java. In Kotlin, null safety is achieved through a system of nullable and non-nullable types. A non-nullable type cannot hold a null value, while a nullable type can hold either a non-null value or a null value. The compiler will enforce null safety by checking whether null is possible in any given context.

To declare a variable as nullable, you add a question mark to the end of the type like this: String?. You can also use the safe call operator ?. and the null coalescing operator ?: to handle nullable values safely and prevent NPEs. In summary, Kotlin's null safety features provide developers with a safer and more concise way to write code that handles null values, reducing the risk of NPEs and making code more readable and maintainable.

Q. When was the first stable version of Kotlin released?

AnswerKotlin's version 1.0, the first stable version, was published in February 2016. As the first version of Kotlin that JetBrains, the business that created it, officially supported, this release was a significant turning point for the language. Due to this release's compatibility with Java, it was simple to incorporate Kotlin code into already-existing Java projects.

It also introduced many of the essential components of the language, including lambdas, type inference, and null safety. Kotlin has continued to progress and become more well-liked among developers since it was first released. Kotlin has been one of the fastest-growing programming languages since Google declared it a first-class language for Android development in May 2019.

Q. Can Kotlin create a website for you?

Answer- It is unquestionably true that Kotlin is a programming language that can be used to create various software applications, including web applications. It would be best to utilize a web development framework or library that supports Kotlin to create a website using this language. Ktor, Spring Boot, and Vert.x are a few well-liked choices.

You can create Kotlin code to manage HTTP requests, connect to databases, and implement business logic for your web application using one of these frameworks or packages.

Q. Which language program is more legible and concise, kotlin or Java?

Answer- Compared to Java, Kotlin is typically thought to be more readable and concise. Because Kotlin's syntax is intended to be shorter, it can make code simpler to understand and write. Boilerplate code and the verbosity of the Java language are two issues that Kotlin was created to alleviate.

To summarise, Kotlin is typically regarded as more readable and concise, despite Java being a strong and popular computer language. Its clear syntax, and contemporary features might make writing and maintaining code easier. For instance, Kotlin allows type inference and offers a shorter syntax for constructing variables and functions, so you don't always need to state the type of a variable or function argument explicitly.

Q. In Kotlin, can we define variables without specifying their types? 

Answer- Kotlin does, in fact, offer type inference, which enables you to declare variables without mentioning their types directly. The Kotlin compiler can determine its type based on the value assigned to a variable.

Q. How to start REPL in IntelliJ IDEA? 

AnswerTo start the Kotlin REPL (Read-Eval-Print Loop) in IntelliJ IDEA, follow these steps:

  1. Open IntelliJ IDEA and create a new Kotlin project, or open an existing Kotlin project.

  2. Open a Kotlin source file in the project.

  3. Click on the Kotlin logo in the upper-right corner of the editor window, or right-click anywhere in the editor and select "Kotlin REPL" from the context menu.

  4. The Kotlin REPL console will appear at the bottom of the IntelliJ IDEA window.

Alternatively, you can open the Kotlin REPL from the main menu by selecting "Tools" > "Kotlin" > "Kotlin REPL" or by using the keyboard shortcut Ctrl+Shift+Enter on Windows or Linux, or Cmd+Shift+Enter on macOS. Once the Kotlin REPL is open, you can enter Kotlin expressions and statements, which will be evaluated, and the result will be printed to the console. You can also define functions and classes in the REPL, which can be used in subsequent expressions.

Q. Which code compiles faster, Kotlin or Java?

Answer- Normally, Kotlin and Java have similar compilation speeds. Both use the Java Virtual Machine (JVM) to execute code, and the Kotlin compiler generates Java bytecode, which is then executed by the JVM. However, Kotlin's language features can sometimes make code more complex, which can increase compilation times, But it performs type-checking than Java compiler, which affects compilation speed. Additionally, the Kotlin compiler is designed to perform more type-checking than the Java compiler, which can also affect compilation speed.

Ultimately, Kotlin's compilation speed may not always be faster than Java's; generally, it is considered fast enough for most use cases. The language provides many other benefits that can make code easier to read, write and maintain.

Q. Which variable is changeable val or var?

Answer- Val is an immutable variable in Kotlin, which means that its value cannot be altered once it has been initialized. However, var can have its value modified after it has been initialized because it is a mutable variable.

Q. In Kotlin, can we assign null to any custom class object?

Answer- Kotlin by default, forbids assigning null values to variables or properties of a custom class type. This is because Kotlin prioritized null safety and was created to prevent null pointer exceptions and enhance code safety. However, a custom class type can be made nullable by explicitly declaring it as such with the? Operator.

Q. What will be the output of the following code? for (i in 1..5 steps 2) println(I)?

Answer- The code for (i in 1..5 steps 2) println(i) in Kotlin will output the values 1 and 3, with a step of 2. Let's dry-run the code:

  • 1..5 is a range that includes the integers from 1 to 5 (inclusive).
  • Specifies that the loop should iterate through the range with a step size of 2.
  • The loop assigns each range value to the variable i in turn.
  • On each iteration of the loop, the value of i is printed to the console using the println() function.

Q. What will be the output of the following code? for (i in 's'..'z' step 2)  println(I)?

Answer- The step function will work the same as the previous one, and since there are characters, the output of the following program will be 'suwy'.

Q. for (i in 'd' .. 'm' step 2) println (i)

AnswerThe step function will work the same as the previous one, and since there are characters, the output of the following program will be 'dfhjl'.

Quiz Complete


We have now gone through some key questions from this article about Kotlin. I hope you were able to learn something from this. If you run into any problems or have any questions about the problems, please feel free to contact me or leave a comment below. Thank you for reading.

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