Top 10 Kotlin Interview questions

Although both Java and Kotlin are used for Android app development, it is hard to choose a better one. This is because both have their pros/cons and are dominant programming languages.

Advantages of using Java:

• It has a straightforward and readable syntax.
• It is a pure form of OOPS
• It has a faster compilation speed than Kotlin
• Some features of Android studio, like auto-complete and compilation, run faster.

Advantages of using Kotlin:

• It is comparatively easy to learn than Java
• It does not have the legacy baggage that Java has been carrying around for a long time.
• It is packed with modern programming features, making development a lot easier.
• It has a safer and smarter compiler as compared to Java.

As you can see, both of these languages have their advantages and disadvantages. So, the actual question you must be asking yourself is, what are my needs and what’s best for my project.

Yes, you can execute a Kotlin code without the help of a JVM.

String interpolation is a variable substitution having its value inside a string. In Kotlin, the $ character is used for interpolating a variable, and the ${} is used to interpolate an expression. Kotlin allows users the liberty of accessing variables and expressions directly from the string literals, thus eliminating the need for concatenation.

Kotlin is an open-source programming language that entirely runs over the virtual machine for its proceeding. This language executes utilizing the Java platform and it was developed by JetBrains. This language is quite simpler than most of its variants specially Java.

All of its codes are converted into native quotes that are processed by the byte code conversion where it refers to the object-oriented programming language.

Structural expressions refer to the representative form of the loops in Kotlin. There are three important expressions which are:

• Break- this expression helps the user to break the nearest enclosing loop
• Return- this expression helps the user to return the nearest functions or any other default functions.
• Continue- this expression helps the user to proceed further for the next loop.

If you are looking for a decent set of questions then you can categorize it under the best Kotlin interview questions for experienced professionals.

Developers which are used to personalize declarations are known as modifiers and there are four types of modifiers available in Kotlin.
These modifiers are

• Public- all the declarations are visible here
• Internal- it uses the declarations present on specific locations
• Private- declarations are contained in restricted files
• Protected- here declarations are secured and usually not available for top-level declarations.

Some of the significant extension methods used in Kotlin are-

• Read texts () - it is helped to read the content present in files to a single string
• Buffer reader () - it is used to read the files to buffer reader
• Read each line () - it is used to read the lines by the following line after line
• Headlines () - it helps to read the content for listing.

The classes which are used to hold the data or content are known as data classes. Earlier these data classes were only used to build the codes in Java but following the explicit implementation of its higher and greater set of properties, it is significant in kotlin as well. Along with this language, functions like tostring, equals are also combined with it. Kotlin offers a variety of these functions by implementing them along with the component functions.

Basically, strings refer to a collection of various characters altogether. There are two types of strings present in Kotlin which are-

• Raw strings
• Escaped strings

Under these strings, templates can also be evaluated easily and this evaluation is known by term as string template interpolation.

Data types are the instances of consonants or variables tending to decide the type of variable. It also specifies the space required for the storage of these variables.

The data types are-

• Numbers
• Characters
• Strings
• Arrays
• Booleans

Note: This is one of the significant kotlin interview questions asked in most interviews.

There are two types of constructors in Kotlin which are-

• Primary constructor- It is a specific section of class header and mostly it is always declared after the class name.
• Secondary constructor- This section of the constructor is always declared inside the class.

Inline Functions

Used to prevent the object allocations for the functions or lambda expressions that have been called.

Infix Functions

It is used for calling functions without any parentheses or brackets.

If you give default values to all the primary constructor values, you shall automatically create an empty constructor for data class.

For example, if you have a data class like this:

data class Activity(
   var updated_on: String,
   var tags: List,
   var description: String,
   var user_id: List,
)

And you want to initialize the data class with an empty constructor, all you have to do is assign the default values to all the primary constructors, like this:

data class Activity(
   var updated_on: String = "",
   var tags: List = emptyList(),
   var description: String = "",
   var user_id: List = emptyList(),
)

Here’s how to initialize an array in Kotlin.

In Kotlin, you should use var where the value of the variable is changing very frequently. A good example would be getting the location of an android device: var integerVariable : Int? = null

Whereas, Val should be used in a case where there would be no change of value throughout the whole class. For example, setting the value of text view or maybe a button’s text through code:

val stringVariables : String = "Button's Final Text"

Here is the best way to create a singleton class in Kotlin:

In Kotlin, if you need to write a code for a function that can be called without a class instance but it needs access to the internals of a class, you can use a companion object declaration in that specific class.

Null safety, also known as void safety is a guarantee that no object references shall have null or void values.

Nullable types in Kotlin are a type of reference which are declared by putting a “?” behind the String.