Kotlin interview questions

When it comes to finding a position or job in the Android Development field, Kotlin is one of the most popular programming languages. Kotlin is a new age, open-source statically typed programming language used by the majority of professional Android developers that helps boost code safety, productivity, and developer satisfaction. 

To succeed in Kotlin and to ensure that we secure a Kotlin interview, we must give it our best shot. Here are some Kotlin Interview Questions to assist us in meeting and achieving our objectives.

In this article, we will discuss some top Kotlin interview questions for freshers to assist them to land a secure job in the field. Let’s get started with the Kotlin interview questions. 

Kotlin Interview Questions

1. How does Kotlin work on Android?

Solution: Kotlin code is compiled into Java bytecode and executed at runtime by the Java Virtual Machine, or JVM, just like Java code. When a Kotlin file named Main.kt is built, it will eventually become a class, and the class's bytecode will be created. The bytecode file will be called MainKt.class, and it will be run by the JVM.

2. What do you understand about Companion Object in the context of Kotlin?

Solution: In some languages, such as Java, there are static keyword to declare class members and utilise them without constructing an object, i.e. by simply calling them by their class name. There is no such thing as a “static” keyword in Kotlin. As a result, we employ companion objects to achieve the functionality of static member functions.

3. What are the types of variables declared in Kotlin?

Solution: 

var s = “kotlin”

• Immutable variables: Read-only variables are another name for immutable variables. The val keyword is used to declare them. We can't change the values of these variables once they've been defined.
• Mutable variables: In a mutable variable, the value of the variable can be changed. We use the keyword “var” to declare such variables.

4. Explain the concept of null safety in Kotlin.

Solution: Kotlin's type system aims to eradicate null references from the code. When a program throws Null pointer exception there is a chance of system failure, to avoid these conditions Kotlin provides Safe Call (?.), Elvis (?:) and Not Null Assertion (!!) operators which define what needs to be done in case of a null encounter.

5. What are the different types of constructors available in Kotlin?

Solution: 

• Primary Constructor  – This type of constructor is initialised in the class header and is provided after the class name. It is declared using the “constructor” keyword.
• Secondary Constructor – This constructor allow for the initialization of variables as well as the addition of logic to the class. They have the constructor keyword prefixed to them

6. Explain the various methods to iterate over any data structure in Kotlin

Solution:

• For Loop – In this case, the for loop is used to scan any data structure that provides an iterator.
• While Loop – It consists of a code block and a condition that must be verified for each iteration. The while condition is checked first, and if it is true, the code within the block is run untill the condition turns false.
• Do While Loop – After all of the statements in the block have been executed, the condition is evaluated. The code block is re-executed if the do-while condition is true. The code block execution procedure is repeated as long as the expression evaluates to true.

7. What do you understand about function extension in the context of Kotlin?

Solution: We can use extensions in Kotlin to add or remove method functionality without inheriting or changing them. Extensions are resolved statistically. Rather than changing the existing class, it provides a callable function that can be invoked with a dot operation.

Function Extension – The function extension feature in Kotlin allows users to specify a method outside of the main class.

8. What do you understand about Companion Object in the context of Kotlin?

Solution: The companion objects are used to achieve the functionality of static member functions (as in java). Object Extension is another name for this.We must use the companion keyword in front of the object definition to construct a companion object.

9. Differentiate between open and public keywords in Kotlin.

Solution: The keyword “open” refers to the phrase “open for expansion.” The open annotation on a class allows others to inherit from it. In Kotlin, a class cannot be inherited by default. An open method in Kotlin can be overridden, whereas it cannot be overridden by default. Rather, any Java method can be overridden by default.

All classes in Kotlin are final by default. If no visibility modifier is specified, the public is used by default, implying that our declarations will be visible throughout the program.

10. Explain about the “when” keyword in the context of Kotlin

Solution: The “when” keyword is used in Kotlin to substitute the switch operator in other languages such as Java. A specific block of code must be run when a certain condition is met. It compares all of the branches one by one until a match is found inside the when expression. It proceeds to the end of the when block and executes the code immediately following the when block after finding the first match.

11. What are the advantages of Kotlin over Java?

Solution: 

• In Java, you must create getters and setters for each object, as well as properly write hashCode, toString, and equals. In Kotlin, data classes take care of everything.
• In kotlin we have extension functions whereas in Java we don’t have that feature.
• Android which have got lots of APIs needs better support for Null safety which is provided by Kotlin.
• There is less space for error because it is more concise and expressive than Java.

That was all about kotlin interview questions.

Conclusion

In this article, we have extensively discussed the kotlin interview questions and answer series covering the beginner-level kotlin Interview questions.

akshaysharma12 Member since May 18, 2022