Kotlin First introduced in 2011 by JetBrains, and was found to be a major participant in the world of software engineering and made a major impact across various communities of developers. By the Java development team of JetBrains, Kotlin was built with the intention of being a more concise and expressive alternative to writing in Java which at the same time still easily interfaces with Java. This thorough guide will meticulously explore Kotlin's components, syntaxes, and the dos and don’ts along with the best practices, therefore, you will be able to gain the optimal knowledge of this contemporary programming tool and implement it in your own projects if you wish.
Core Syntax and Language Features
Variables and Data Types
Kotlin is all about simplicity that means its code is usually close to plain English hence; declaring a simple and clear logic for this programming language is not the hardest thing. By using 'val' keyword, we can create a new immutable variable and 'var' keyword in order to make a new mutable variable as follows.
val I_can_t_be_changed: String = "I can't be changed"
var number_of_mutable: Int = 42
number_of_mutable = 50 // This is allowed
Another feature of Kotlin is type inference, which means that sometimes you don't have to declare the type of the data at all:
val is_inferred_as = "Kotlin will infer this as a String"
var is_inferred_as = 100 // Inferred as Int
Null Safety
Yet another favorite space for many tech minds is Kotlin that has been inserted because of its effective approach to null safety that is responsible for preventing the users from unintended errors when using classes. Variables cannot be null by default unless question marks are added after them, that is, when nullable only.
var can_be_null = "This can't be null"
var result: String? = "This can be null"
result = null // This is allowed
Moreover, Kotlin enables the user to employ its "safe call operator (?)." and "Elvis operator (?:)" to successfully work with such a type as nullable:
val length = result?.length ?: 0
Functions
The declaration of Kotlin functions goes with the 'fun' keyword to start with, which is followed by the parameters, the return type, and the default arguments in brackets:
Now I have a function of Kotlin called "greet" for greeting some areas in the name of "World" but in case of no name has been entered in this line, it calls "Hello, World!".
Kotlin has, for the rest, become equipped with single-expression function, and then, we can write them in a more concise way:
fun area(x: Int) = x * x
Control Flow
What factors are exceptional in Kotlin in the place of other available ones, are familiar control flows with certain improvements. The "when" expression is strongly recommended to be treated as a common usage instead of switch statements:
fun describe(obj: Any): String =
when (obj) {
1 -> "One"
"Hello" -> "Greeting"
is Long -> "Long number"
!is String -> "Not a string"
else -> "Unknown"
}
Object-Oriented Programming in Kotlin
Classes and Objects
Kotlin simply and efficiently employs class declarations that can directly contain properties within the primary constructor:
class Person(val name: String, var age: Int)
// Usage
val alice = Person("Alice", 30)
println("${alice.name} is ${alice.age} years old")
Data Classes
In addition to the classic classes that can contain or may not contain a certain number of fields whose states are fixed, there are the so-called data classes that are generally concretely presented and ought to be used in architecture, DTO, or other like things, for example, a vehicle/data class is the best choice when they are only intended to keep a set of records. They are then also primarily used for getting the string, checking if they are equal, or hashing the contained variables respectively:
data class User(val name: String, val email: String)
Inheritance and Interfaces
Kotlin with the facilities of single inheritance and substitutable implementation of one or more interfaces makes it possible to develop whole programs without using the complex classes of C++ and Java. Kotlin offers runtime polymorphism, that is, it can have two or more methods with the same name and different behavior that is automatically recognized by the parameters used for calling them. Also, the use of interfaces allows you to add a new ability to another class well in the future. This way "animal" will be the parent class the other classes like dog and fish will derive from "animal" class and thus take advantage of the "makeSound" procedure which does an animal noise (takes the name of an animal as an argument), and the rest of the program stays the same with the only addition of the child classes "Dog" and "Fish".
open class Animal(val name: String) {
open fun makeSound() {
println("The animal makes a sound")
}
}
class Dog(name: String) : Animal(name) {
override fun makeSound() {
println("The dog barks")
}
}
interface Swimable {
fun swim()
}
class Fish(name: String) : Animal(name), Swimable {
override fun makeSound() {
println("The fish doesn't make a sound")
}
override fun swim() {
println("The fish swims")
}
}
Functional Programming in Kotlin
Lambda Expressions
Google's new environment of Kotlin will give the freedom possibility for many companies from generating fairly expensive and time-highly demanding projects for whatever typically are quantified by productivity through the developments and modifications in the software of their products or the software that sustains their businesses based on the user experience by greatly including user involvement in this process. That is, Kotlin, in conjunction with functional programming, can do more than just processing data, it can provide first-class functions and lambda expressions as well:
val numbers = listOf(1, 2, 3, 4, 5)
val number_squares = numbers.map { it * it }
println(number_squares) // Output: [1, 4, 9, 16, 25]
Higher-Order Functions
The functional parts in the Kotlin programming language allow both acceptance and returning the functions in the functions:
fun operation(x: Int, y: Int, op: (Int, Int) -> Int): Int {
return op(x, y)
}
val sum = operation(10, 5) { a, b -> a + b }
val product = operation(10, 5) { a, b -> a * b }
Extension Functions
A unique feature of the Kotlin programming language is the allowance to add new functions (extension functions) to existing classes without rewriting them:
fun String.removeFirstAndLast(): String {
return this.substring(1, this.length - 1)
}
println("Hello".removeFirstAndLast()) // Output: ell
Coroutines for Asynchronous Programming
Kotlin’s coroutines are not designed only to help programmers but also to make the code done while asynchronous programming. It is a way of writing code where some parts of the program are executed not in order (for example, the main program does not execute printing one line after the other but either orange is first or red is second as a result). However, the execution of the remaining part of the code is not delayed (the program still goes on running) by not executing that part immediately, yet you will be able to control when it will be done through the launching mechanism used in these cases. It is a wonderful technique that will enable you to write asynchronous code in a linear-like way thus it is easier to follow and maintain even for a developer who has just begun his/her career in Android development or any other programming field.
import kotlinx.coroutines.*
fun main() = runBlocking {
launch {
delay(1000L)
println("World!")
}
println("Hello")
}
// Output:
// Hello
// World!
Structured concurrency is a term used in computer science that refers to the practice of organizing concurrent code into a fixed structure or pattern. It makes the code easier to understand and maintain. There are some details but they are too technical.
Interoperability with Java
The main advantage that will be crucial to Java language in its long life ahead is the built-in version to kotlin-jvm-standalone in case you don't use a suitable plugin, but Maven or Gradle can help in this using the commands:
// Java class
public class JavaClass {
public static void sayHello() {
System.out.println("Hello from Java!");
}
}
// Kotlin code
fun main() {
JavaClass.sayHello()
}
With the interoperability between Kotlin and Java, you can even combine Kotlin and Java projects. It also makes it easier for you to gradually migrate from Java to Kotlin in case you have already had some existing Java projects and now you want to incorporate Kotlin for better performance and new features.
Real-World Applications of Kotlin
Android Development
The growing usage of the Kotlin programming language on Android was a breakthrough for Android developers and was a real innovation. It is just a matter of choice now whether to be a Java-only developer or a multi-linguist Android developer who has added Kotlin as the second language. Kotlin includes lots of beneficial features such as Guarded Objects(Pattern) and Streamed Exception model that significantly enhance the overall development process. It's not a big deal that you have not taken these benefits, in any case, the Handbook and web Pages about Kotlin the advocate is a good chance for programmers to learn Kotlin as an example since they can follow its steps to get started, rather than forcefully do the work.
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
findViewById(R.id.button).setOnClickListener {
Toast.makeText(this, "Hello, Kotlin!", Toast.LENGTH_SHORT).show()
}
}
}
Server-Side Development
Kotlin is also a good server-side development language. Ktor is just a top platform for server-side development. It has various tools like Unit tests, performance tests, maintenance scripts, and others. Besides, the framework builds the server using threads, thanks to the Netty handler. It creates the server that will be used in the tutorial by adding a route to it.
import io.ktor.application.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
fun main() {
embeddedServer(Netty, port = 8080) {
routing {
get("/") {
call.respondText("Hello, Ktor!")
}
}
}.start(wait = true)
}
Data Science and Analysis
Kotlin's strong typing and syntactic shortcuts facilitate practical data manipulation and avoid the kind of errors that plague weakly-typed and/or verbose languages. Furthermore, with an ample list of libraries specifically built for Kotlin, such as Kotlin for Apache Spark, the program development will be very convenient as the program is supposed to be written in a set of instructions. Such programs should be written in mainly kotlin language as before and also be run from the linux terminal; mainly, not any special tools are needed to be run to conduct these programs like setting up the python environment on a windows/linux machine and then importing crawling libraries.
import org.apache.spark.sql.SparkSession
import org.jetbrains.kotlinx.spark.api.*
fun ArithmeticExcercise() = withSpark {
val numbers = spark.range(1, 100).toDS()
val sum = numbers.map { it * 2 }.reduce { acc, value -> acc + value }
println("Sum: $sum")
}
Kotlin's Ecosystem and Tools
Build Tools
It's common to use Gradle or Maven as build tools for JVM languages, otherwise, you won't be able to use the IntelliJ IDE. Invoking these tools as automation tools is very important to have your system built and deployed successively. Their full names are Gradle-based and Open-source and by their help accessibility, the management of Android.context class will be released and introduced into the open-source community.
plugins {
kotlin("jvm") version "1.5.0"
}
repositories {
mavenCentral()
}
dependencies {
implementation(kotlin("stdlib"))
}
Testing Frameworks
Kotlin is a language that is used in the automotive industry and in the industries that have to do with sales. It is a general language that is being used in various industries and various applications are being developed using Kotlin. Nonetheless, there are still concerns about programming languages and how they are used and work.
import io.kotlintest.shouldBe
import io.kotlintest.specs.StringSpec
class MyTests : StringSpec({
"length should return size of string" {
"hello".length shouldBe 5
}
})
IDE Support
Kotlin has a great relationship with the IntelliJ IDEA Integrated Development Environment (IDE) and the Android Studio. Proper integration is what is mostly appreciated by the commentator in this question that the Kotlin provides the programs with features such as code completion, refactoring, debugging, that could only be provided to it by the Android Studio and other editors and discover code which is inaccessible to the human eyes and are mostly written in the woods behind the Eiffel Tower.
Best Practices and Idioms
Use Expression Bodies
Developers have found that it is much faster and simpler in writing the code of them by taking the progressive development methodology as the preferred one in a growing number of regulation-compliant programming environments that demand the teamwork of specialists of different disciplines. Usually, for simple functions, you want to return a value in a few lines of code, so use expression body instead of a block body as it is more concise.
fun double(x: Int) = x * 2
Prefer Val over Var
Using 'val' on read-only variables most of the time helps one to become a coder who, for the most part, does not likethen to modify the variables, who finds it easy to work with code that needs to be changed by few options, which have the possibility of showing the list of constants that don't change.
val pi = 3.14159
Use Data Classes for DTOs
When a class is all about holding data, making it a data class is the best approach:
data class CustomerDto(val name: String, val email: String)
Leverage Kotlin's Standard Library
Kotlin, on the other hand, supplies an opportunity and requires that one not code the solution of a problem through the usual well-outlined paths, but let him/herself to follow through his/her innovative thoughts of how to do it with the help of Kotlin's implemented standard library:
val numbers = listOf(1, 2, 3, 4, 5)
val evenNumbers = numbers.filter { it % 2 == 0 }
Use Scope Functions
Scope functions are a way which Kotlin, a very easy-to-use programming language and designed language for that matter, treats objects by applying special functions to them. 'Let' is quite possibly the best tool for optional work especially now that the language has different alternatives. These include: run, with, let, and also as examples of these subtyping concepts. However, which one to apply exactly depends on the situation.
person?.let {
println(it.name)
println(it.age)
}
Conclusion
Kotlin has successfully stepped into the software development world by slightly making its own way for modern, versatile, and powerful kinds of programming while being lightweight, concise, and natively interoperable with Java. Notably, Kotlin is chosen widely for its reliability of delivering clean and safe code. A developer should exploit new possibilities for creating applications run more easily, safely, and elegantly by understanding Kotlin. The language is mainly known for developing applications for Android devices. However, it can be used on a server-side, for example, with the use of the Ktor framework which makes the task of creating asynchronous servers easy.
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1 Comments
Thx Guys For Support .. !!
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