30 Asked Kotlin Interview Questions and Answers (2024)

Ques 26. What do you understand about sealed classes in Kotlin?

Kotlin introduces a crucial new form of class that isn't seen in Java. These are referred to as "sealed classes." Sealed classes, as the name implies, adhere to constrained or bounded class hierarchies. A sealed class is one that has a set of subclasses. When it is known ahead of time that a type will conform to one of the subclass types, it is employed. Type safety (that is, the compiler will validate types during compilation and throw an exception if a wrong type has been assigned to a variable) is ensured through sealed classes, which limit the types that can be matched at compile time rather than runtime.

Ques 27. What do you understand about the backing field in Kotlin?

A backing field is an auto-generated field for any property that may only be used inside accessors (getter or setter) and will only be present if it utilizes the default implementation of at least one of the accessors, or if a custom accessor refers to it through the field identifier. This backing field is used to avoid an accessor's recursive call, which would result in a StackOverflowError.

Fields are not allowed in Kotlin classes. When employing custom accessors, however, it is occasionally required to have a backing field. Kotlin includes an automatic backing field for these purposes, which may be accessed by the field identifier.

For example,

var marks: Int = someValue       
get() = field       
set(value) {           
  field = value       
}

Explanation:- Here the field identifier acts as a reference to the property “marks” value in the get() and set() method. So, whenever we call the get(), we get the field’s value returned. Similarly, whenever we call the set(), we set the “marks” property value to “value”.

Ques 28. Differentiate between launch / join and async / await in Kotlin.

launch / join:-

The launch command is used to start and stop a coroutine. It's as though a new thread has been started. If the code inside the launch throws an exception, it's considered as an uncaught exception in a thread, which is typically written to stderr in backend JVM programs and crashes Android applications. Join is used to wait for the launched coroutine to complete before propagating its exception. A crashed child coroutine, on the other hand, cancels its parent with the matching exception.

async / await:-

The async keyword is used to initiate a coroutine that computes a result. You must use await on the result, which is represented by an instance of Deferred. Uncaught exceptions in async code are held in the resultant Deferred and are not transmitted anywhere else. They are not executed until processed.

Ques 29. What are some of the disadvantages of Kotlin?

Following are some of the disadvantages of Kotlin:

In Kotlin, there are a few keywords that have non-obvious meanings: internal, crossinline, expect, reified, sealed, inner, open. Java has none of these.
Checked exceptions are likewise absent in Kotlin. Although checked exceptions have become less prominent, many programmers believe them to be an effective technique to ensure that their code is stable.
A lot of what happens in Kotlin is hidden. You can almost always trace the logic of a program in Java. When it comes to bug hunting, this can be really useful. If you define a data class in Kotlin, getters, setters, equality testing, tostring, and hashcode are automatically added for you.
Learning resources are limited. The number of developers who are moving to Kotlin is growing, yet there is a small developer community accessible to help them understand the language or address problems during development.
Kotlin has variable compilation speed. In some situations, Kotlin outperforms Java, particularly when executing incremental builds. However, we must remember that when it comes to clean builds, Java is the clear winner.

Ques 30. What’s the Target Platform of Kotlin? How is Kotlin-Java interoperability possible?

Java Virtual Machine(JVM) is the Target Platform of Kotlin. Kotlin is 100% interoperable with Java since both, on compilation produce bytecode. Hence Kotlin code can be called from Java and vice-versa.

Kotlin Interview Questions and Answers

Related differences

Ques 26. What do you understand about sealed classes in Kotlin?

Ques 27. What do you understand about the backing field in Kotlin?

Ques 28. Differentiate between launch / join and async / await in Kotlin.

Ques 29. What are some of the disadvantages of Kotlin?

Ques 30. What’s the Target Platform of Kotlin? How is Kotlin-Java interoperability possible?