Java vs Kotlin: What is difference between Kotlin and Java?

If you are interested in developing an android application and you are in a dilemma about which language to choose, then this article is for you. In this article, we will help you to decide which language to pick i.e., Java or Kotlin.

So, let's get started.

What is Java?

Java is an object-oriented programming language, developed by Sun Microsystems(now the product of Oracle). It is widely used as the server-side language for most backend development projects. It is a platform-independent, easy-to-learn programming language that is designed for building object-oriented programing language. Also, it is a multithreaded programming language with automatic memory management. It is considered as one of the fast, secure, and reliable programming languages that are preferred by most of the organization for project building.

Example of Java Program

public class Main
{ 
	public void Name(String fName, String lName) {
    	String Name = fName + " " + lName;
		System.out.println("The student's name is : " + Name); 
	}     
    public void Age() { 
	    int age = 18;
        System.out.println("The student's age is : " + age); 
	}     
    public void Address() {
        String address ="Mumbai";
        System.out.println("The student's address is : " + address); 
    }
	public static void main(String args[]) { 
		Main m = new Main(); 
		m.Name("John","Stewart");
        m.Age();
        m.Address();
	} 
} 

The student's name is: John Stewart
The student's age is: 18
The student's address is: Mumbai

Advantages of Java

1. It is an open-source language that ensures safety.
2. It is easy to use and compile. Also, it makes debugging and deploying simpler.
3. It is an object-oriented programming language that reuses the parts which contribute to robustness.
4. It is platform-independent.

What is Kotlin?

Kotlin is a newly created programming language developed by Google. It is inspired by Java but is an improved version of it with many additional features. It is widely used for Android App Development. It is an open-source statically typed programming language that targets the JVM, Android, JavaScript, and Native. It is faster to compile and easy to learn. It is mainly focused on interoperability, safety, clarity, and tooling support. It is supported by all the major IDEs including AndroidStudio, Eclipse, and NetBeans.

Example of Kotlin Program:

class Main {
    fun Name(fName: String, lName:String) {
        var Name = "$fName $lName"
        println("The student's name is : $Name")
    }
}
fun Age() {
	var age : Int
    age = 19
    println("The student's age is: $age")
}
fun Address(){
    var address : String
    address="Delhi"
    println("The student's address is: $address")
}
fun main(args: Array<String>) {
    Main().Name("Mike","Stewart")
    Age()
    Address()
}

The student's name is: Mike Stewart
The student's age is: 19
The student's address is: Delhi

Advantages of Kotlin:

1. It can use all JavaFrameworks and Libraries.
2. It is easy to learn and is approachable.
3. It compiles to JVM bytecode or JavaScript.
4. It is faster to compile, light-weight, and prevents the application from increasing its size.

Java Issues that are addressed in Kotlin:

These are some of the Java issues that are addressed by Kotlin:

1. Function Types - Kotlin has proper function types, as opposed to Java’s SAM-conversions. In simpler terms, in Kotlin, a lambda expression or an anonymous function can access the variables declared in the outer scope.
2. Exceptions - Java supports the concept of checked Exceptions whereas Kotlin does not have any checked Exceptions. This is because in Kotlin all the exception classes are the descendants of the class Throwable.
3. Null Safety - Kotlin uses in-built null safety variables whereas Java uses a class for null handling.
4. Invariant Arrays - Kotlin helps to overcome the Runtime failure which is one of the major issues faced in Java. Arrays in Kotlin are invariant as it does not allow a user to assign an Array<Sring> to Array<Any>.
5. No Raw Types
6. Use site variance without wildcards - Kotlin doesn't have any Wildcard Types. So, to use any site variance just Type Projections and declaration-site variances.

Why Choose Kotlin?

These are some of the following concepts that Kotlin has, but Java doesn't:

• Extensions Functions: This is a new feature that is introduced in Kotlin that allows a class to have new functionality without extending it.
• Smart casts: In Kotlin, we use '!is' or 'is' to check on a variable, the compiler tracks this information and automatically casts the variable to the targeted type.
• Singletons: Sometimes a user wants to create an object with slight modifications of some class, but without explicitly calling declaring a new subclass for it. This can be generalized in Kotlin by using object expressions and declarations. Moreover, this is not restricted to final variables like in java.
• Null Safety: It is safe against NullPointerException
• Data Classes: Data Class in Java is used for creating classes to hold the data. Basically, they are regular classes but with some additional functionality. One of the major advantages of using data classes in Kotlin is that it helps to reduce the amount of boilerplate code.
• Coroutines: Kotlin uses the concept of coroutines. Coroutines are light-weight threads that excel in short non-blocking tasks. But there is a difference between coroutines and threads. Coroutines are sequential in nature whereas threads can work in parallel.
• Companion Objects: In Kotlin, if any function or any member of the class needs to be called without having the instance of the class, then it can be written as a member of the companion objects inside the class.
• Lambda Expression: In Kotlin, brackets are always required and hence helps with readability.

Why Choose Java?

These are some of the following concepts that Java has, but Kotlin doesn't:

• Concurrency: Java uses the concept of threads to support concurrency.
• Lambda Expression: In Java, the parenthesis are more lenient i.e., it depends on the number of parameters. For example, if the number of parameters is one then there is no need for parenthesis.
• Checked Exceptions: Java supports the concepts of checked exceptions.
• Static members: Java supports the concept of static members.
• Model Class: Java uses the concept of getters and setters, along with the isEqual or toString methods when accessing the properties.

Comparison Chart

Let us look at the comparison table for a better understanding.

Basis Of Comparison	Java	Kotlin
Null Safety	No	Yes
Lambda Expression	No	Yes
Invariant Array	No	Yes
Non-Private Fields	Yes	No
Smart Casts	No	Yes
Static Members	Yes	No
Wildcard Types	Yes	No
Singleton Objects	Yes	Yes
Compilation	Bytecodes	Virtual Machine

So, in this article, we saw what is the difference between Kotlin and Java. And I hope this article will help you decide which language to choose Java or Kotlin.

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