Java is a widely popular programming language that has been used for years in various domains, including web development, mobile app development, desktop applications, and game development.

On the other hand, Kotlin is a relatively new programming language that has been gaining popularity in recent years. Both languages are used to build applications for the Java Virtual Machine (JVM), but they differ in terms of syntax, features, and performance.

Java has been around for quite some time and has a vast community and a plethora of libraries. On the other hand, Kotlin is a relatively new language that offers contemporary features and concise syntax, which makes it an appealing alternative for developers.

In this article, we will discuss the differences between Kotlin and Java.

Differences Between Kotlin and Java

Syntax

One of the most significant differences between Kotlin and Java is the syntax. Kotlin has a more concise syntax than Java, which means that it requires less code to perform the same operations.

For example, let's compare the syntax for creating a class in both languages:

//java

public class MyClass {
   private int myField;

   public MyClass(int myField) {
      this.myField = myField;
   }

   public int getMyField() {
      return myField;
   }

   public void setMyField(int myField) {
      this.myField = myField;
   }
}

//kotlin

class MyClass(private var myField: Int) {
   fun getMyField() = myField
   fun setMyField(value: Int) { myField = value }
}

As you can see, the Kotlin version is much more concise and readable than the Java version. In Kotlin, we can define the class and its fields in a single line, and the getters and setters are replaced with property accessors.

Additionally, Kotlin supports type inference, which means that you do not have to specify the data type of a variable explicitly.

//kotlin

val myString = "Hello, world!"

As seen in the Kotlin code above, we can use type inference to declare a variable without explicitly specifying its data type. The compiler will automatically determine the data type based on the value that we assign to the variable. This can make our code more concise and easier to read.

//java

String myString = "Hello, world!";

In the Java code above, you are required to specify the data type of the variable which can make your code more verbose.

Here is another example showing the difference between the verbose syntax of Java and a more concise Kotlin syntax.

//java

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

The code above is a simple "Hello, World!" program in Java that prints “Hello, World!” to the console.

//kotlin

fun main() {
    println("Hello, World!")
}

As you can see, the Kotlin version is much shorter and more expressive. Kotlin achieves this by eliminating unnecessary boilerplate code, such as type declarations and semicolons, and using more natural language constructs.

Null Safety

Both Kotlin and Java compile to bytecode that runs on the JVM, which means they have similar performance characteristics.

But Kotlin has some performance advantages over Java in certain cases. For example, Kotlin's null safety feature can help reduce the number of runtime exceptions and improve the overall performance of the application. And Kotlin's use of immutable data structures can also lead to improved performance.

Null safety is another area where Kotlin differs from Java. In Java, it's possible to have null values assigned to a variable, which can lead to null pointer exceptions at runtime. Kotlin, on the other hand, requires you to explicitly define whether a variable can be null or not. This makes it easier to avoid null pointer exceptions during runtime.

For example, in Kotlin, all variables are non-null by default, meaning that they cannot hold a null value unless explicitly declared as nullable using the "?" operator. This helps to prevent null-related errors at compile-time, rather than waiting until runtime.

//kotlin

var name: String = "John" // non-null variable
var age: Int? = null // nullable variable

Functional Programming

Another significant difference between Java and Kotlin is their support for functional programming. While Java has added some support for functional programming in recent years with the release of Java 8, Kotlin was designed from the ground up to support functional programming concepts.

For example, Kotlin supports lambda expressions, higher-order functions, and extension functions. These features make it easier to write code that is both concise and expressive and can help to improve code quality. Here is a code sample showing this:

//kotlin
// lambda expression
val list = listOf(1, 2, 3)
val doubledList = list.map { it * 2 }

// higher-order function
fun higherOrderFunc(x: Int, y: Int, f: (Int, Int) -> Int): Int {
    return f(x, y)
}
val result = higherOrderFunc(3, 4) { x, y -> x + y }

// extension function
fun Int.isEven() = this % 2 == 0
val isFourEven = 4.isEven()

Conclusion

In summary, Kotlin and Java are both awesome programming languages that have some significant differences. While Java is a more established language with a large community and extensive libraries, Kotlin provides modern features and concise syntax, making it an attractive choice for many developers.

Kotlin's focus on null safety and support for functional programming make it well-suited for modern application development, while Java's performance and library ecosystem make it a good choice for enterprise applications.

Ultimately, the choice between Java and Kotlin will depend on the specific needs of your application and your development team's preferences and skills.

I hope this article was informative.
Happy learning.