Kotlin Basic interview Question : most asked Kotlin interview Question and answer for Freshers

Kotlin Basic interview Question: The developer of well-known IDEs like Android Studio and IntelliJ IDEA, JetBrains, is the brains behind the contemporary programming language Kotlin. Kotlin is a language designed to be secure, expressive, and compact. It has become quite popular in the past few years, especially among Android developers.

Because Kotlin and Java are completely compatible, you can easily include Kotlin code into already-existing Java projects. Because of this, developers can more easily transition to Kotlin over time without having to completely redo their apps. Null safety, which helps avoid frequent programming problems associated with null pointer exceptions, is one of Kotlin’s primary characteristics. Furthermore, Kotlin has a number of features including data classes, coroutines, and extension functions that help streamline development and enhance the readability of code.

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

When expressions, like switch statements in other languages, are useful for conditional branching in Kotlin. It offers a clear and understandable method for checking various situations and executing particular code blocks in response to those criteria. When in Kotlin offers significant benefits over typical switch statements.

First, when has the ability to function as both a statement and an expression. It returns a value based on the matching condition when used as an expression. This enables you to use the outcome of a when expression directly in other expressions or assign it to a variable. Second, Kotlin’s when expressions support more conditions, such as regular expressions, in-ranges, and ranges. Complex problems are easier to address because of this versatility. Lastly, to handle scenarios that don’t match any of the given requirements, expressions can include an else branch. This helps to ensure that your code is thorough and prevents unexpected errors.

2. Differentiate between open and public keywords in Kotlin.

In Kotlin, open and public keywords both control the visibility of classes, members, and functions, but they serve different purposes.

Classes, members, and functions are all reachable from anywhere in the project thanks to the public keyword. For members and classes, this is the visibility modifier by default. It permits extensive access and reuse across several application components.

Inheritance and overridability are the main uses of the open keyword. A class that has been declared open can use inheritance to be expanded by other classes. Open can also be used on members and methods to enable subclasses to override them. This allows for the creation of class hierarchies that are more adaptable and versatile, facilitating polymorphism and code reuse.

3. What do you Know about Companion Object in the context of Kotlin?

In Kotlin, companion objects are a unique concept that enables you to attach static functionality to a class. Companion objects are independent of class instances, in contrast to static members in other languages. Rather, they are connected to the class itself.

This lets you define members, functions, and other attributes in a companion object that you can use without having to make an instance of the class. Frequently, companion objects are utilized to offer factory methods, utility methods, or constants associated with a specific class. For instance, you could use a companion object to offer static-like constants that are frequently used throughout the application or to construct a factory function that generates instances of the class based on particular parameters.

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

Kotlin’s function extensions are a strong feature that let you extend the functionality of pre-existing classes without changing the source code. To do this, functions that are defined outside of a class are linked to a particular receiver type.

The compiler automatically gives the object as a hidden argument to an extension function when you call it on an object. This gives you access to the methods and properties of the object from within the extension function. When adding common or commonly used actions to pre-existing classes, function extensions come in handy because they eliminate the need to establish new subclasses or alter the original class specification. Your code may become more manageable, legible, and succinct as a result.

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5.Explain the concept of null safety in Kotlin.

One important aspect of Kotlin that helps avoid typical programming problems associated with null pointer exceptions is null safety. Kotlin has a distinction between nullable and non-nullable types, unlike many other languages.

The inability to assign a null value to non-nullable types guarantees that their variables and attributes always have a meaningful value. By doing this, you can lessen the likelihood of runtime problems happening when you try to access a null object’s function or property. However, nullable types have the ability to be assigned a null value; this is denoted by a question mark (?) following the type. Working with nullable types requires you to use methods like the let function, the Elvis operator (?:), or the safe call operator (?.) to deal with the potential of null values. By doing this, you can make sure that your code is resilient and treats null data with care.

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6.  How does Kotlin work on Android?

Kotlin effortlessly incorporates into the environment for Android development. Use of Kotlin as the primary programming language is an option available to you when creating an Android project with Android Studio. Because of Kotlin’s compatibility with Java, developers who know both languages can work on the same project and combine Kotlin and Java code.

The Android Virtual Machine (AVM) runs Java bytecode that has been compiled from Kotlin code underneath. This procedure makes sure that Kotlin apps don’t need extra runtime support to function on a variety of Android devices. Android developers can write cleaner, more dependable, and more manageable code with the help of Kotlin’s succinct syntax, null safety, and other capabilities.

7.What is a primary constructor in Kotlin?

In Kotlin, a unique type of constructor implicitly defined as part of the class header is called a main constructor. The primary constructor has a separate constructor keyword, in contrast to secondary constructors, which are defined directly within the class body. Rather, it is stated in parenthesis after the class name.

It is possible for the main constructor to take parameters, which are automatically transformed into class properties. Either the class header or the class body may explicitly define these properties. Initializer blocks are invoked after the parameters are initialized in the main constructor. This gives the constructor a practical means of carrying out extra initialization logic.

8.What is a data class in Kotlin?

In Kotlin, classes that are primarily used to hold data can be succinctly defined using data classes. Based on the attributes declared in the class, they automatically build a set of boilerplate methods, like equals, hashCode, toString, copy, and componentN functions.

By doing away with the necessity to manually implement these methods, this makes the process of constructing classes—which are mostly used to represent data structures—much simpler. When working with collections of data or creating models for Android applications, for example, you frequently need to store and handle data objects. In these cases, data classes come in handy. You may ensure that your data objects are correctly compared, hashed, and represented as strings while writing code that is easier to read and understand by utilizing data classes.

9.What is the default behavior of Kotlin classes?

Kotlin classes are not inheritable and are final by default. This suggests that you can’t create subclasses of a class unless it’s marked as open explicitly. This prevents unintentional modifications to pre-existing classes and promotes code encapsulation.

Still, Kotlin has an abstract class creation technique as well. Although abstract classes are not immediately instantiable, they can serve as basis classes for other classes. Concrete subclasses of abstract classes are required to implement any abstract members that they may include. This lets you specify an interface that all linked classes will use, but the subclasses will handle the implementation details.

10.Does Kotlin provide support for primitive Datatypes?

Unlike languages like Java, Kotlin does not contain primitive data types. Rather, every data in Kotlin—including those that translate to Java primitive types—uses reference types. Null safety and the ability to execute operations on these types more consistently are two benefits of this approach.

In Kotlin, an object is internally represented by the compiler when a primitive type variable is declared. This implies that you can call methods and access properties on these kinds using the same syntax as you would for regular objects. Furthermore, to help avoid frequent programming errors, Kotlin’s type system makes sure that these primitive types are not nullable by default.

11.What are the advantages of Kotlin over Java?

• Simple Process: In Java, every object requires the creation of getters and setters. In addition, writing equals and hashCode is necessary. Nevertheless, classes in the Kotlin programming language handle everything, simplifying the process.
• Rewriting the method: If you use Java, you must replicate or rewrite the getter and setter methods for each variable. This takes time. The rewriting portion is much faster in Kotlin.
• Support for Extensions: Extension functions are not available in Java. On the other hand, Kotlin offers robust support for extension functions that help to clarify the overall workflow and programming language.
• No/less Errors: Compared to Java, Kotlin has less opportunities for errors.

12.How do you differentiate val and var declaration?

In Kotlin, val and var are used to declare variables, but they differ in their mutability:

“Value” (abbreviated “val”) is used to declare variables that are immutable, which means that once they are initialized, their values cannot be altered. A val variable maintains its value across its scope after it is assigned one. This is comparable to Java’s last keyword.

“Variable” is denoted by the symbol “var,” which is used to declare variables whose values are modifiable at any moment. A var variable can have several values assigned to it during the course of its lifespan. This is similar to a Java regular variable.

12.What’s the Elvis Operator?

In Kotlin, handling null data can be done succinctly and readablely with the Elvis Operator (?:). It is a ternary operator that, in the event that the expression on the left is not null, returns that value; in the other case, it returns the value on the right.

When working with nullable types, this operator is very helpful because it offers a practical means of providing a default value or carrying out other actions in the event that a value is null. For instance, if a nullable property is null, you can use the Elvis Operator to provide a default value for a variable:

13. What’s the entry point of the Kotlin Program?

The primary purpose of a Kotlin program is its entry point. Your code runs from this function as its initialization point. The Java Virtual Machine (JVM) searches the designated class or package for a main function when you execute a Kotlin program.

14.Define the type of constructors in Kotlin?

Primary: The class headers highlight the primary constructors. They cannot coexist in a way that makes sense. As a result, each class has a single primary constructor aligned.

Secondary constructors : Secondary: The class body identifies secondary constructors. They can coexist with rationality. More than one secondary constructor can be specified.

15.Define the init block in Kotlin?

An init block is a unique code block in Kotlin that is run automatically when a class instance is created. It’s a practical method of doing out initialization operations, including initializing resources or setting default values for attributes, that are shared by all instances of a class.

Init blocks are implicitly executed, as contrast to constructors, which are called explicitly to build objects. A class may have more than one init block, and those blocks are performed in the sequence that they appear. This facilitates the organization of initialization logic and guarantees that some jobs are completed before others.

16.Do you identify ‘new’ as a keyword in Kotlin?

No, the new keyword is not available in Kotlin. Compared to languages like Java, where new is used to generate new instances of objects, this is a big shift.

Object instantiation is done more directly and succinctly in Kotlin. Once a class is declared, all it takes to generate instances of it is to call the class name, just like you would a function.

17.What is a range in Kotlin?

A sequence of numbers with an ordered start and end point is referred to as a range in Kotlin. A continuous set of numbers, letters, or other values can be represented using ranges.

In Kotlin, there are two primary categories of ranges: closed ranges and half-open ranges. Half-open ranges contain the start value but not the end value, whereas closed ranges have both the start and end values. The range operators until (half-open range) and.. (closed range) can be used to generate ranges.

18.How do you use the “invoke” operator in Kotlin?

In Kotlin, the invoke operator is a unique operator that lets you call an object that behaves like a function just like a conventional function would. This is very helpful when making objects that can be callbacks or higher-order functions.

All you have to do to utilize the invoke operator is define a class or object that has an invoke function. This object automatically invokes the invoke function when you call it as a function.

19.What is String Interpolation ?

You can embed expressions within strings using a powerful feature called string interpolation, which is supported by a wide range of computer languages. It offers a clear and understandable method for creating dynamic strings by simply replacing function calls or variable values into the string template. This makes the code cleaner and easier to maintain by doing away with the necessity for manual concatenation using string operators.

When you use string interpolation, the expression is enclosed in delimiters (usually dollar signs or curly brackets). The interpreter of the language then evaluates the expression and replaces it with the value that corresponds to it within the string. Because of this runtime dynamic substitution, you can write strings that change their meaning based on context or varying input values.

20.Can you explain the concept of extension functions in Kotlin?

With Kotlin’s strong extension functions, you may extend the functionality of existing classes without changing the original source code. Declaring functions outside of the class with a receiver type that indicates the class to be extended is how this is accomplished. An object of the receiver type responds to an extension function call as though it were a member of that class.