Ans: It is an open-source programming language that combines object-oriented programming features.
The features like Range Expression, Extension Function, Companion Object, Smart casts, Data classes are considered to be a surplus of the Kotlin Language.
Ans: Kotlin was developed by JetBrains.
Ans: In programming, we use classes to hold data and these classes are called as data classes.
An object can be initialized in the data class and to access the individual parameters of these data classes, we use component functions.
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fold - takes an initial value, and the first invocation of the lambda you pass to it will receive that initial value and the first element of the collection as parameters.
listOf(1, 2, 3).fold(0) { sum, element -> sum + element }
The first call to the lambda will be with parameters 0 and 1.
Having the ability to pass in an initial value is useful if you have to provide some sort of default value or parameter for your operation.
reduce - Doesn't take an initial value, but instead starts with the first element of the collection as the accumulator (called sum in the following example)
listOf(1, 2, 3).reduce { sum, element -> sum + element }
The first call to the lambda here will be with parameters 1 and 2.
Ans: Kotlin supports only two types of programming, and they are:
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Ans: There are two types of constructors in Kotlin:
Ans: Since Kotlin simplifies many syntactical elements of Java, it’s easier to write concise, well-documented code. Additionally, since it runs directly on JVM, enterprises hardly need to invest in new tech stacks. So the cost-benefit adjustment is excellent.
Moreover, Kotlin has already started to replace many Java-based Android apps, alongside iOS apps written in Swift. This number will only increase over time and adapting to Kotlin will become a must for modern enterprises. So, to stay ahead of the competition, developers should embrace Kotlin today.
Ans: Some of Kotlin’s best features are-
Ans: Kotlin comes with in-built protection against unwanted null references which allows it to be more fault-tolerant. It thus allows programs to reduce NullPointerExceptions during runtime and prevents unwanted program crashes. This is a common problem faced by most existing Java software and causes losses costing millions of dollars. This is often coined as Null Safety among Kotlin developers.
Ans: There are three Structural expressions in Kotlin.
They are:
Ans: The modifier in Kotlin provides the developer to customize the declarations as per the requirements.
Kotlin provides four modifiers.
They are:
Ans: In Kotlin, you can assign null values to a variable by using the null safety property. To check if a value is having null value then you can use if-else or can use the Elvis operator i.e. ?: For example:
var name:String? = "Mindorks"
val nameLength = name?.length ?: -1
println(nameLength)
The Elvis operator(?:) used above will return the length of name if the value is not null otherwise if the value is null, then it will return -1.
Ans: Steps to convert your Kotlin source file to Java source file:
Ans: In Kotlin, we can't use primitive types directly. We can use classes like Int, Double, etc. as an object wrapper for primitives. But the compiled bytecode has these primitive types.
Ans: Abstraction is the most important concept of Objected Oriented Programming. In Kotlin, the abstraction class is used when you know what functionalities a class should have. But you are not aware of how the functionality is implemented or if the functionality can be implemented using different methods.
Ans: Data types of a constant or variable decide what type of variable it is and how much space is required to store it.
The basic data types in Kotlin are:
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Advantages:
Kotlin is simple and easy to learn as its syntax is similar to that of Java.
It is the functional language that is based on JVM (Java Virtual Machine), which removes the boilerplate codes. Upon all this, Kotlin is considered as an expressive language that is easily readable and understandable and the performance is substantially good.
It can be used by any desktop, web server or mobile-based applications.
Disadvantages:
Kotlin does not provide the static modifier, which causes problems for conventional java developers.
In Kotlin, the function declaration can be done in many places in the application, which creates trouble for the developer to understand which function is being called.
Ans: Kotlin functions are first-class functions that are easily stored in variables and data structures and can be pass as arguments and returned from other higher-order functions.
Sample function declaration and usage in Kotlin
fun double(x: Int): Int {
return 2 * x
}
val result = double(2)
Ans: Some of the extension methods are:
Ans: Inline function instruct compiler to insert complete body of the function wherever that function got used in the code. To use an Inline function, all you need to do is just add an inline keyword at the beginning of the function declaration.
Ans: While using an inline function and want to pass some lambda function and not all lambda function as inline, then you can explicitly tell the compiler which lambda it shouldn't inline.
inline fun doSomethingElse(abc: () -> Unit, noinline xyz: () -> Unit) {
abc()
xyz()
}
Ans: Formal inheritance structure does not compile in the kotlin. By using an open modifier we can finalize classes.
open class B
{
}
class c = B()
{
}
Ans: Init is a login block and it is executed in the primary constructor and initialized. If you want to revoke in the secondary constructor then it starts working after the primary constructor in the chain form.
Ans: String processing comprises an essential portion of any app development. Interviewees are often asked how to handle this during Kotlin interview questions. You can use the equality operator ‘==’ to do this, as demonstrated by the following example.
val a: String = "This is the first string"
val b: String = "This is the second" + "string"
if (a == b) println("The Strings are Similar")
else println("They don't match!")
Ans: Loops are a crucial programming construct that allows us to iterate over things as our program requires. Kotlin features all the commonly used loops such as for, while, and do-while. We’re describing the for loop in a nutshell in the following section.
val sports = listOf("cricket", "football", "basketball")
for (sport in sports) { // for loop
println("Let's play $sport!")
}
The above snippet illustrates the use of the for loop in Kotlin. It’s quite similar to Python and Ruby.
Q28. What is the Purpose of Object Keyword?
Ans: Kotlin provides an additional keyword called object alongside its standard object-oriented features. Contrary to the traditional object-oriented paradigm where you define a class and create as many of its instances as you require, the object keyword allows you to create a single, lazy instance. The compiler will create this object when you access it in your Kotlin program. The following program provides a simple illustration.
fun calcRent(normalRent: Int, holidayRent: Int): Unit {
val rates = object{
var normal: Int = 30 * normalRent
var holiday: Int = 30 * holidayRent
}
val total = rates.normal + rates.holiday
print("Total Rent: $$total")
}
fun main() {
calcRent(10, 2)
}
Kotlin data types define the procedures available on some data. The compiler allocates memory space for variables using their data type. Like many popular programming languages, Kotlin features some often-used data types. Take a look at the below section for a short overview of various Kotlin data types.
Ans: String interpolations work with multiple placeholders and first evaluate their value to display the final string output. This final output will contain the corresponding values of the placeholders. The below code snippet will illustrate a simple example of Kotlin string interpolation.
fun main(args: Array<String>) { // String Interpolation
print("Please enter your name here:")
val name:String? = readLine()
print("Hello, $name!")
}
Here, the Kotlin compiler first receives the user input and interpolates this value in place of the placeholder $name. The last line of the snippet is translated by the compiler as shown below –
new StringBuilder().append("Hello, ").append(name).append("!").toString()