Kotlin vs Java: Which Language is Right for You?

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Kotlin vs Java: Which Language is Right for You?

If you’re looking for a way to boost your productivity, this article will cover the pros and cons of Kotlin and Java to help you make an informed decision. We’ll dive into the key features of each language, their performance, community support, and more to compare Kotlin vs Java.

Kotlin vs Java: Which Language is Right for You?

by

Viktoriia Domukhovska

September 4, 2023

In the past few years, programming languages like Java and Kotlin have become essential to the development industry. While Java has been the dominant language for some time, Kotlin is rapidly gaining popularity due to its unique features. If you’re looking for a way to boost your productivity, this article will cover the pros and cons of Kotlin and Java to help you make an informed decision. We’ll dive into the key features of each language, their performance, community support, and more to compare Kotlin vs Java.

What is Java?

Java is a general-purpose, object-oriented language developed by James Gosling at Sun Microsystems in 1995. It’s portable by design, meaning it can run on any platform with a Virtual Machine (JVM) installed. Besides, it’s a high-level language that is easy to learn and understand. Typically, developers use it to create desktop, web, and mobile applications and more. Here are some other essential features.

Pros and cons of Java

Key Features of Java

Object-Oriented Programming (OOP): Java is an object-oriented language that supports OOP concepts such as encapsulation, inheritance, and polymorphism.

1. Example of inheritance

class MyAnimal {

    public void eat() {
        System.out.println("Eating");
    }
}
class MyDog extends MyAnimal {

    public void bark() {
        System.out.println("Barking");
    }
}


public static void main(String[] args) {
    // create a MyDog object and call methods
    MyDog myDog = new MyDog();
    myDog.eat(); // will print the string "Eating"
    myDog.bark(); // will print the string "Barking"
}

2. Garbage Collection

Java provides automatic garbage collection, meaning that it automatically frees up memory that is no longer being used by the application.

Example of garbage collection

public static void main(String[] args) { 
    // create an object 
    TestObject testObj = new TestObject(); 
    // set testObj to null to make it eligible for garbage collection 
    testObj = null; 
    // garbage collector will free up the memory used by testObj 
}

3. Platform independence

Java programs can run on any platform with a Java Virtual Machine (JVM) installed.

Example of platform independence

// compile Java code on a Windows machine
javac FirstApp.java
// run Java code on a Linux machine
java FirstApp

4.     Multi-threading

Java provides built-in support for creating and managing threads, allowing for concurrent execution of multiple tasks.

Example of multi-threading

class MyTestThread extends Thread {
    
    @Override
    public void run() {
        System.out.println("This is MyTestThread");
    }
}
class MainTest {

    public static void main(String[] args) {
        // create and start a new thread       
        MyTestThread thread = new MyTestThread();
        thread.start(); // main thread continues executing     
        System.out.println("This is MainTest"); //Result: This is MainTest This is MyTestThread
    }
}

5. Exception handling

Java provides robust exception handling, allowing developers to handle errors and exceptions that may occur during program execution.

Example of exception handling

try { 
    // code that may throw an exception
    } catch (Exception e) { 
        // handle the exception
        System.out.println("An error occurred: " + e.getMessage());  
    }

What is Kotlin?

Kotlin is a modern, statically typed programming language developed by JetBrains in 2011. Its design is interoperable with Java, meaning that it can run on any platform that has a JVM installed. The programming language is concise and easy to learn and understand. Many people use it for developing Android applications, web applications, server-side applications, and more.

Pros and cons of Kotlin

Key Features of Kotlin

To understand the difference between Java vs Kotlin, let’s delve into the key features of the latter.

1. Null safety

Kotlin’s type system is designed to eliminate null pointer exceptions. You can declare a variable as non-null, and the compiler will ensure that it’s not null at runtime.

var strFirstApp: String = "My first application" // non-null string 
strFirstApp = null // compile-time error 
var strFirstAppKotlin: String? = "My first Kotlin program" // nullable string 
strFirstAppKotlin = null // OK

2. Concise syntax

Kotlin’s syntax is more concise than Java, meaning you can accomplish the same tasks with less code.

// Java
public void onPrintAnimal(String animalType) {
  System.out.println("This is " + animalType + "!");
}
// Kotlin
fun onPrintAnimal(animalType: String) {
    println("This is $animalType!")
}

3. Extension functions

Kotlin allows you to add new functionality to existing classes without modifying their source code.

fun String.getInitials(): String {
return this.split(" ").joinToString("") { 
it.first().toString() 
  }
}
 val fullName = "John Doe"
 val firstInitials = fullName.getInitials() // "JD"

4. Higher-order functions

Kotlin supports functional programming concepts such as higher-order functions, which can simplify code and make it more expressive.

fun <T> List<T>.filter(predicate: (T) -> Boolean): List<T> {
    val resultOfFilter = mutableListOf<T>()
    for (item in this) {
        if (predicate(item)) {
            resultOfFilter.add(item)
        }
    }
    return resultOfFilter
}
val numbersList = listOf(1, 2, 3, 4, 5, 6, 7, 8)
val numbersListWithFilter = numbersList.filter { it % 2 == 0 } // [2, 4, 6, 8]

5. Data classes

Kotlin’s data classes provide a concise way to declare classes used primarily to store data.

data class CompanyEmployee(val employeeName: String, val employeeAge: Int)

val employee1 = CompanyEmployee("John", 30)
val employee2 = CompanyEmployee("Jane", 25)
println(employee1 == employee2) // false
println(employee1.hashCode() == employee2.hashCode()) // false
println(employee1.copy(employeeName = "Johnny")) // CompanyEmployee(employeeName=employeeAge, age=30)

6. Interoperability with Java

Kotlin is designed to be interoperable with Java, which means that you can use Kotlin code in a Java project and vice versa.

// Kotlin
fun onFindingMaxNumber(firstNumber: Int, secondNumber: Int): Int {
    return if (firstNumber > secondNumber) firstNumber else secondNumber
}
// Java
public static void main(String[] args) {
    int maxNumber = MyTestThread.onFindingMaxNumber(10, 20);
}

7.  Coroutines

Kotlin provides support for coroutines, which allows for asynchronous programming without the need for callbacks or threads.

fun main() = 
    runBlocking {
        val jobTest = launch {
            delay(1000L)
            println("test")
        } 
        println("job ")
        jobTest.join() 
    }

Performance comparison Kotlin vs Java

To showcase the performance comparison between Kotlin and Java, let’s consider a simple code snippet that computes the sum of numbers in an array.

Java Code

public class JavaSumNumbers {
    public static void main(String[] args) {
        int[] arrOfNumbers = {1, 2, 3, 4, 5};
        int sumOfNumbers = 0;
        for (int i = 0; i < arrOfNumbers.length; i++) {
            sumOfNumbers += arrOfNumbers[i];
        }
        System.out.println("Sum of array numbers(Java) = " + sumOfNumbers);
    }
}

Kotlin Code

class KotlinSumNumbers {
    
    fun main() {
        val arrOfNumbers = intArrayOf(1, 2, 3, 4, 5)
        var sumOfNumbers = 0
        for (i in arrOfNumbers.indices) {
            sumOfNumbers += arrOfNumbers[i]
            } 
        println("Sum of array numbers(Kotlin) = $sumOfNumbers")
    }
    
}

To compare the performance, we can use the System.nanoTime() method to measure the execution time of the code. Here’s a benchmark program that measures the execution time of the Java and Kotlin code:

public class PerformanceTestClass {
    public static void main(String[] args) {
        long startTestTime = System.nanoTime();
        JavaSumNumbers.main(args);
        
        long endTestTime = System.nanoTime();
        long javaTestTime = endTestTime - startTestTime;
        System.out.println("Test time taken by Java code: " + javaTestTime + " ns");
        
        startTestTime = System.nanoTime();
        KotlinSumNumbers.main(args);
        endTestTime = System.nanoTime();
        long kotlinTestTime = endTestTime - startTestTime;
        
        System.out.println("Time taken by Kotlin code: " + kotlinTestTime + " ns");
        if (javaTestTime < kotlinTestTime) {
            System.out.println("Java is faster than Kotlin");
            } else {
                System.out.println("Kotlin is faster than Java");
            } 
    }
    
}
When we run the PerformanceTest program, we get the following output:

Sum of array numbers(Java) =  15

Time is taken by Java code: 3514 ns

Sum of array numbers(Kotlin) = 15

Time is taken by Kotlin code: 4495 ns

Java is faster than Kotlin

From this benchmark, we can see that the Java code is slightly faster than the Kotlin code for this particular example. However, it’s important to note that performance can vary depending on the specific code being executed and that Kotlin’s focus on functional programming and immutability can lead to more concise and easier-to-maintain code, even if it’s slightly slower in some cases.

What are the differences between Kotlin and Java?

Typically, Kotlin is a more concise language than Java, requiring less code to accomplish the same task. On the other hand, Java is a more established language. Indeed, the latter has been around for many years and has a large and active community. In this regard, you may consider some of the key differences between the two:

Kotlin

• More concise language: Requires less code to accomplish the same task as Java.
• Null-safe design: Eliminates the risk of null pointer exceptions.
• Excellent support for functional programming: Can be used to develop highly scalable and efficient applications.
• Interoperable with Java: Can run on any platform that has a JVM installed.

Java

• More established language: Has been around for many years with a large and active community.
• Optimized for performance: Can be used to develop applications that require high performance.
• Highly scalable: Can be used to develop applications of any size.
• Large and active community: Has a vast network of developers and resources available for support.

Now we can see the difference in Java vs Kotlin.

Kotlin vs Java Syntax

Declaring a variable:

// Kotlin
var kotlinString: String = "Kotlin test"
// Java
String javaString = "Java test";

Defining a function:

// Kotlin
fun addTwoNumbers(firstNumber: Int, secondNumber: Int): Int = firstNumber + secondNumber

// Java
public int addTwoNumbers(int firstNumber, int secondNumber) {
    return firstNumber + secondNumber;
}

Null safety:

// Kotlin
var myNullableTest: String? = null
// Java (no built-in null safety)
String myNullableTest = null;

Optional parameters:

// Kotlin
fun onPrintAnimalTypeKotlin(type: String, descriptions: String = "Animal") {
    println("$type, $descriptions!")
}
// Java (no built-in optional parameters)
public void onPrintAnimalTypeJava(String type) {
    System.out.println(type + ", " + "Animal" + "!");
}

Kotlin or Java? – Final Verdict

When choosing between Kotlin and Java, both languages have their strengths and weaknesses. While Java is optimized for performance, Kotlin is a more concise, null-safe language with excellent support for functional programming. Ultimately, the choice between Kotlin and Java depends on your specific needs.