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Kotlin Interview Questions 1

Kotlin Interview Questions

JetBrains’ Kotlin is a statically typed, general-purpose programming language that has inspired world-class IDEs such as IntelliJ IDEA, PhpStorm, Appcode, and others. JetBrains first announced it in 2011 as a new language for the JVM. Kotlin is an object-oriented language that is a “better language” than Java while remaining completely compatible with Java code.

Kotlin developers are in-demand professionals because of their ability to work on the front end of Android devices. Kotlin developers with industry knowledge and appropriate technical skills can earn to a greater extent and it’s a very diversified field. 

The demand for Kotlin developers is growing day by day. A large number of companies are hiring for this commendable position. Let’s learn about the common interview questions for Kotlin developers to help you ace your interview.

  1. What is Kotlin and what makes it a good choice for Android development? 

Sometimes we just use a class to hold data and nothing else. These are known as Data classes. Of course, these types of classes might be written in Java, but with explicit implementations of getter and setter methods for each of the class’s properties. You may also need to implement functions such as equals, to string, and copy independently. All of this is automatically implemented by Kotlin, coupled with special functions known as component functions. How wonderful is it that the duplicate code bloat has been removed?

Furthermore, Kotlin is fully compatible with Java, allowing developers to easily include existing Java libraries in their Kotlin code and vice versa. Overall, Kotlin is an enticing alternative for Android development due to its simple syntax, robust support for functional programming, and smooth interoperability with Java.

  1. What are the features you think are there in Kotlin but not in Java?

Kotlin has quite several features that Java doesn’t. To name some of them, they are

  • Extension Functions
  • Null Safety
  • Smart casts
  • Range expressions
  • Operator Overloading
  • Data classes
  • Companion Objects
  • Coroutines etc.
  1. What are Data classes? Aren’t they available in Java?

Sometimes we just use a class to hold data and nothing else. These are known as Data classes. Of course, these types of classes might be written in Java, but with explicit implementations of getter and setter methods for each of the class’s properties. You may also need to implement functions such as equals, toString, and copy independently. All of this is automatically implemented by Kotlin, coupled with special functions known as component functions. How wonderful is it that the duplicate code bloat has been removed?

  1. What are the high-order functions, give an example.

Higher-order functions in Kotlin are functions that accept one or more functions as parameters and return a function as a result. Because these functions may be passed around and utilized in multiple situations, they allow for more flexible and modular code. In Kotlin, here’s an example of how to use a higher-order function:

fun processNumbers(numbers: List<Int>, processor: (Int) -> Int): List<Int> { 

    val result = mutableListOf<Int>() 

    for (number in numbers) { 

        result.add(processor(number)) 

    } 

    return result 

 

fun main() { 

    val numbers = listOf(4, 5, 6, 7, 8) 

    val squaredNumbers = processNumbers(numbers) { it * it } 

    println(squaredNumbers) // prints [16, 25, 36, 49, 64] 

}

In this example, the processNumbers function takes two inputs: a function and a list of integers. The function is then applied to each entry in the list, and the results are appended to another list. The main function then calls the processNumbers function, passing a lambda function to square each number. The result is a list of squared numbers. 

These higher-order functions are ideal for modularizing code and increasing its flexibility. They are a powerful Kotlin feature that can dramatically improve the expressiveness and readability of your code. 

  1. Where does this Kotlin run ? Does it have some kind of different runtime environment ?

Kotlin programmes, once compiled, can run on a normal JVM just like any other compiled Java code. This indicates that Kotlin Compiler converts Kotlin programmes to byte-code that JVM can understand. So, Kotlin is a Java flavour that works alongside Java. It’s worth noting that Kotlin applications can be constructed using sections of Java code.

  1. What is the difference between val and var ? 

Val (Value) is similar to a constant. You cannot modify a value once it has been allocated. Var (Variable) on the other hand is intended to be a storage location that can accept the reassignment of values of the same data type or whatever is possible through data type casting.

  1. What is Null safety?

The goal of Null Safety in Kotlin is to eliminate the possibility of a NullPointerException occurring in real time. Kotlin can distinguish between nullable and non-nullable references. If a variable may store a null value, it must be declared with the null (?) operator.

  1. What are extension functions and how do they work in Kotlin ?

Extension functions in Kotlin allow you to add new functions to existing classes without needing to use design patterns like decorators or inherit from existing types. All you need to do is supply the name of the class you want to extend, the dot operator, and the name of the function. 

For example, let’s say you want to add a test() function to the Sample class. You can do this using an extension function like this: 

fun Sample.test() { 

    println(“Testing…”) 

}

Now, you can call the test() function on any object of type Sample just like you would with any other member function: 

val t = Sample() 

t.test()  // Output: “Testing…” 

One of the primary benefits of extension functions is that they allow you to extend the functionality of a class without modifying the class or creating a new subclass. This can help you avoid inheritance overhead and make your code more flexible and reusable. 

Overall, Kotlin’s extension functions are a powerful and valuable tool that can help you write more expressive and readable code. 

  1. What is lambda expression in kotlin and how are they used ?

It is equivalent to an anonymous function in other programming languages, and it allows you to write code that is both straightforward and expressive.  To define a lambda expression in Kotlin, wrap the code block in curly braces and, if necessary, provide the input arguments and return type. The lambda expression can be assigned to a variable or used as a function argument. As an example: 

val sum: (Int, Int) -> Int = { x, y -> x + y } 

val result = sum(4, 2)  // result is 6

The lambda expression sum returns the sum of two numbers as input in this case. The lambda expression is assigned to a variable of type (Int, Int) -> Int, a function type that represents a function with two integer arguments and an integer return type. 

Lambda expressions are commonly coupled with higher-order functions in Kotlin, that is, functions that accept or return them as arguments. Higher-order functions are a good approach to abstract away operations and improve the expressiveness and readability of your code. 

  1. How does Kotlin support destructuring declarations, and how do you use them?

Destructuring declarations in Kotlin allows you to segregate variables from a data object. This can be a helpful approach to access an object’s distinct properties and operating with them independently. 

In Kotlin, destructuring declarations are used to extract individual properties of an object and assign them to independent variables using the component1, component2, etc. functions. These functions are generated automatically for data classes and can be manually implemented for other types. 

For example, consider the following data class: 

data class User(val name: String, val age: Int) 

You can use destructuring declarations to extract the name and age properties of a User object like this: 

val user = User(“Mice”, 55) 

val (name, age) = user 

println(name)  // prints “Mice” 

println(age)   // prints “55” 

In this example, the val (name, age) = user statement decomposes the user object into its name and age properties and assigns them to the variables name and age, respectively. 

Destructuring declarations can be a helpful approach to accessing and operating with an object’s properties individually. They’re especially handy when used with higher-order functions like map and filter, which let you apply a function to a set of data and get back a new set of results. 

I hope you got the idea of what some of the Kotlin developer interview questions could be in your next interview. If you are looking for challenging opportunities at some of the fastest-growing global companies, join Talent500. Sign up here.

 

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Saumya Saxena

Saumya Saxena

iOS enthusiast with 3+ years of experience in the IT industry.
As an iOS developer, I have a strong passion for developing applications. Apart from being into Mobile development, I have been constantly working towards Technical Writing. Working for my passion provides up thrust to me and aids me in pursuing the same as my future career. I believe in working hard.

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