Well, it’s a better option to develop Android apps for driving success to your business, but choosing the best programming language is quite challenging. 

When it comes to programming language, Java reaches many minds as it’s everywhere and used the most. 

But, after Kotlin came to the surface, the popularity of Java started getting weaker, and programmers started getting confused between Java or Kotlin, which one to choose. 

So, to pick you out from such confusion, this post will offer you a clear vision and let you know which one is best for developing an Android app

So, let’s start. 

About Kotlin Programming Language

kotlin logo

First, let’s start with the significant milestones from Kotlin’s history:

  • Kotlin was released in 2016, and Google announced the top-class support of Kotlin in Android in 2017.
  • In 2018, Kotlin v1.3 was launched, carrying coroutines for asynchronous programming. 
  • Next, in 2019, Google proclaimed Kotlin as its most-preferred programming language for Android app developers. 

About Java Programming Language

java logo

Now, let’s know the significant milestones from Java’s history:

  • Initially, Java was known as OAK. Initially developed for managing set-top boxes and portable devices, Oak proved to be a massive failure. 
  • Next, in 1995, Sun named OAK as Java and revised this language to reap the benefits of the burgeoning www (World Wide Web) development business.
  • In the last quarter of 2009, Oracle Corporation acquired Sun Microsystems and caught up with three critical Sun software assets: MySQL, Java, and Solaris. 

What Is Kotlin?

An improved version of Java, Kotlin embraces various add-on features of Java. It is easy to clean, learn, and demands fewer formalities and rules than Java. The developers need to know the basic programming language to understand Kotlin better. 

Offerings of Kotlin

Kotlin carries along with various traits, like:

  • SafetyBy design, safety is likely to avoid common software defects. 
  • ReadabilityLanguage features, such as data classes, type interface, and infix functions, assist with readability. Such traits assist in writing compact code maintaining easy readability. 
  • InteroperabilityBecause of interoperability, Java, and Kotlin can coexist, which facilitates Kotlin libraries and frameworks in Java. 
  • Implicit DelegationKotlin supports implicit delegation by using the composition over inheritance design pattern. Ahead, class delegation offers the possibility of holding multiple inheritances. 
  • SingletonsKotlin eases the declaration of a singleton just by declaring an object. Ahead, the initialization of singleton object is achieved on the first access and is also thread-safe. 
  • Range ExpressionsKotlin supports the range expressions using the rangeTo function which is quite useful to craft and iterate over a range of values, hence promoting readable and shorter code. 
    Similarly, the downTo operator is useful to iterate over a range in the reverse order. 
  • Infix NotationIt’s a function with just one parameter. Infix Notation permits us to call it with no parentheses that make the function call looks like natural language
  • Named and Default ArgumentsKotlin offers an alternative to method overloading. A function can hold named parameters that permit us to call a function with its parameters in a distinct order. Moreover, named parameters can enhance the code’s readability. 
  • PragmaticAs Kotlin is crafted for large-scale enterprise software development, pragmatism holds importance, and JetBrain uses it to develop its IDEs. Resultantly, Kotlin merges feedback from the industry and locates the difficulties relevant to large-scale software development. 

What Is Java?

An open-source and object-oriented, general-purpose programming language, Java includes fewer dependencies. Being secure, fast, and reliable, Java is mostly used for developing supercomputers, game consoles, cell phones, and data centers.

  • Offerings of JavaJava is mostly picked as it arrives with its various offerings, like:
  • Application Environment – Java is a standalone program and doesn’t need a browser for code execution.
    Moreover, it’s viewed as a general-purpose language, and that’s why it runs on any machine installed with JRE. 
  • Independent FeaturesJava includes 83 libraries and is comparatively more accessible for developers to use its libraries. Despite compiling and optimizing native code on various devices, Java facilitates independent features for Android development. 
  • Robust Memory ManagementThis language is robust as it arrives with fantastic memory management. Moreover, Java doesn’t use pointers to prevent security issues; instead, it utilizes the idea of references. 
  • Development Environment – Java technology contains many tools, such as an interpreter, compiler, documentation generator, and packaging tool.

Kotlin App Development Architecture

app development with Kotlin clean architecture
Source: Cobeisfresh

Java App Development Architecture

java architecture
Source: Javatpoint

Difference Between Kotlin And Java

Now, after getting some picks from the history of both the languages, their definitions, offerings, and more, we will move on to the difference between them. 

1. Checked Exceptions

In Kotlin, we can’t find checked exceptions. So, developers don’t require to catch or declare the oddities that come with advantages and disadvantages. 

Whereas, in Java, we have the checked exceptions that demand declaration and catch the exception by developers, resulting in robust code with better error handling. 

Winner: Java is winning as it offers checked exceptions to maintain code robustness. 

2. Smart Casts

In Kotlin, smart casts help handle these casting checks with the “is-checks” keyword that holds the caliber to perform implicit casting and check for immutable values. 

In Java, we must check the type of variables and cast them as per the operation. 

3. Functional Programming

Kotlin is a blend of functional and procedural programming language that includes various valuable methods, like operator overloading, lambda, lazy evaluation, higher-order functions, etc. 

Until Java 8 was released, Java didn’t include functional programming. But, while building Android apps, it backs just a subset of Java 8 features. 

Winner: Kotlin wins here as it was released to lower down the code and make the complete process easy for the developers. 

4. Coroutines Support

Kotlin facilitates the creation of various threads to run such long-running intensive operations. Still, we have coroutines support that at a certain point stops execution without blocking the threads while executing the long-running intensive operations. 

Whenever we start a long-running network CPU Intensive operations or I/O, the connected thread gets blocked in Java. Android is by-default single-threaded, and Java offers the caliber to craft various threads in the background and next run them. But, their management is quite complex. 

5. Null Safe

By default, in Kotlin, all sorts of variables are non-nullable, which means we can’t assign null values to any objects/variables). If we attempt to return or give null values, the Kotlin code will fail during compile time. Still, if we want a variable to hold a null value, we can declare it as:

value num: Int? = null

In Java, NullPointerExceptions make the developers frustrated. It permits users to assign null to any variables. Although accessing an object reference holding a null value boosts a null pointer exception that users have to handle.

6. Data Classes

In Kotlin, if we want classes for holding data, we can declare a class using the keyword “data” in the class definition. Next, the compiler handles further acts, like creating setter methods for different fields, constructors getter, etc. 

In Java, if we want to have a class that can hold data and nothing else, we need to define variables to store data, constructors, getter and setter methods, toString(), hashcode(), and equals() functions. 

Winner: Here, Kotlin is the winner as it facilitates the accessible design of the data classes compared to Java. 

7. Extension Functions

Kotlin offers the developers the caliber to improve an existing class with the new functionality. Also, it permits the creation of extended functions by prefixing the class name to the new function name. 

In Java, when it comes to extending the functionality of the existing class, we need to build a new class and inherit the parent class. So, in Java, Extension functions are not available. 

8. Type Inference

Inference type is called the type constraint issue, which a type constraint can resolve. You don’t need to declare the type of every variable based on the assignment. In Kotlin, it will automatically be handled. 

Moreover, explicit specification is allowed in this. 

In Java, while declaring, you need to mention the type of each variable. 

9. Lambda Expression

Ahead, with Kotlin, you can use lambda expressions or anonymous functions. These are known as “functional literal.” Therefore, it showcases a function that’s not declared and instantly passes as an expression. 

Java arrives with lambda expressions, a function that can be crafted without even belonging to a class. In Java, lambda expressions can be passed as objects and executed on demand. 

10. Variable Datatype Specifications

Kotlin doesn’t need any variable datatype specifications. 

Java needs variable datatype specifications.

11. Semicolon

Kotlin programs don’t need semicolons in their program. 

Java programs demand a semicolon. 

12. Language Scripting Capabilities

Kotlin provides language scripting power to use the language directly into your Gradle build scripts.

Java doesn’t permit programmers to use language scripting power. 

13. String Templates

There are two types of string literals in Kotlin: escaped string and raw string.

Kotlin string template also supports expression.

Available in Java too, but it doesn’t support expressions like Kotlin. 

14. Operator Overloading

Kotlin facilitates the users to emerge with a way to invoke functions. Moreover, it allows performing equality checks, an arithmetic operation, or comparing any object we need through the symbols, such as +, -, *, /, <, >, %

In Java, operators are linked to specific Java types. For example, String and numeric types can use the + operator for addition and concatenation in Java, and other Java types can’t use this operator again. 

15. Type System

Kotlin offers type interfaces, nullability support, and universal guards. 

In Java, there are many sorts of reference types relevant to the class’s basic concept. 

16. Static Members

In Kotlin, the companion object makes static members of the class. Inside a class, an object declaration can be written with the companion keyword. 

Static members in Java are used mainly for memory management. You can apply Java static keywords with methods, variables, nested classes, and blocks. 

17. Constructors

In Kotlin, we can have one or even more secondary constructors. 

In Java, users can’t have secondary constructors but multiple constructors. 

18. Use Cases

Kotlin is another most-popular programming language that is also the most picked language for Android development.

Java is the general-purpose JVM programming language. That’s why, it’s usually preferred for varied projects, such as backend apps and standalone apps. 

19. Wildcard Types

No, wildcard-types are not there in Kotlin but hold two other things, embracing type projections and declaration-site variance. 

In Java, you can find a wildcard that showcases an unknown type, and you can use it in distinct situations. 

20. Public Fields

Kotlin doesn’t come with public fields. 

In Java, public fields and non-private fields are convenient when the object callers need to change as per the exact object’s representation. It permits the developer to modify an object’s representation with no need to change the callers. 

21. Implicit Conversions

Kotlin doesn’t support implicit widening conversions. That’s why smaller types can’t be converted to bigger types. To fix this, Kotlin developers need to execute an explicit conversion to attain the required type of conversion. 

On the contrary, Java supports implicit conversions, which means the developers don’t need to conduct explicit conversions. 

22. Platform Compatability

Apart from supporting bytecode, Kotlin supports JavaScript also, but native code compilation. 

Java compiles to bytecode for JVM and to JS using Rhino and Nashorn JS Engines. 

23. Primitive Types

In Kotlin, as you create a variable of a primitive type, it will automatically be considered as an object. 

In Java, variables of a primitive type are not the objects, instead, they are predefined Java’s data types. Java comes with the right distinct primitive data types: int, byte, float, short, double, boolean, long, and char. Hence, these variables can’t be an object depicted from a class or a struct. 

Although, primitive types are not classes. Java developers can utilize classes that can hold primitive type values. To accomplish this using Java, the developer should explicitly indicate it.

24. Lazy Keyword

Yes, it’s available in Kotlin. It lowers startup time that holds significance in the development of apps using Kotlin. 

It’s not available in Java.

25. Sealed Classes

Kotlin implemented the sealed classes concept from the beginning only. 

Whereas Java introduced it as a preview feature in Java 15. As of Java 17, sealed classes are part of the language altogether. In Java, a sealed class should define explicitly which classes can extend it. For that, we can utilize the reserved identifier ‘permits.’ 

In Java, you can inherit only classes in the same module.

In Kotlin, you need to define subclass in the same file. 

In Kotlin, you can inherit any class in this file from a sealed class. In Kotlin, an object type is used in the switch statement.

Whereas Java showcases pattern matching for its switch statement just as a preview feature in Java 17. 

Top Apps Developed Using Kotlin

Some of the top Android apps built using Kotlin programming language are:

  • Uber
  • Airbnb
  • Tinder
  • Pinterest
  • Netflix

Advantages Of Kotlin

Let’s check out the benefits of Kotlin:

  • Kotlin comes with in-built safety support that proves to be a lifesaver, specifically for Android as it’s packed with old Java-style APIs. 
  • It assists the developers to build extension functions. 
  • Kotlin provides understandable and user-friendly coding norms. 
  • It uses various specialized languages structures and function types, such as lambda expression. 
  • It offers an almost automated and simple way to create data classes.
  • Moreover, Kotlin is easy to read and write as it’s a statistically-typed language.
  • It divides big apps into smaller layers.
  • Kotlin permits the use and exchange of information from Java in many ways. 
  • Furthermore, it is more expressive and concise than Java, which says there’s no possibility of errors. 
  • In Kotlin it demands less time to write new code.
  • Utilizing the Kotlin Multiplatform framework, we can extract one common codebase that will mark all simultaneously.
  • Moreover, in Kotlin, it’s quite simple to deploy code and maintain it at scale.

Disadvantages Of Kotlin

Now, it’s time to know the cons of Kotlin as we need to pick the best to develop our apps. 

  • The proficient Java programmers find it tough to choose Kotlin. Hence, it may need extra expenses to arrange Kotlin training. 
  • Kotlin was released almost 6 years back and 8% and even more developers have switched onto Kotlin. Because of limited support from the community and resources, it’s becoming tough for the developers to meet the challenges in the development phase. 
  • With Kotlin, we will witness the slow performance and this is the main restriction of Kotlin. In some situations, Kotlin performs well than Java when it comes to compilation speed, but it’s usually considerably lower. 
  • While conducting incremental builds, Kotlin pace up faster. Although, to craft clean build for Android apps, Java is the champ. 
  • Bytecode is the compiled format that’s used for the Kotlin programs. It states, once the developer programs code and assembles it, it doesn’t run through the computer’s processor, instead of through a virtual machine. 
  • When a new feature gets integrated by JetBrains into IntelliJ, a developer can convert from Java to Kotlin easily and save time. Also, you don’t need to retype mundane code for Kotlin. 
  • The main benefit of using this language is that we can still use every existing Java library and framework. 
  • The best part of Kotlin is that developers can easily integrate with Gradle, Maven, and other developed systems. 
  • With Kotlin, you don’t need to fret about NullPointerExceptions. Kotlin’s system will assist you to prevent null pointer exceptions. If we compare both Kotlin and Java, Kotlin’s system doesn’t compile code that returns or assigns null. 

Major Projects In Java

Let’s check out the top projects in Java that are gaining success:

  • LinkedIn
  • Twitter
  • Spotify
  • Cash App

Advantages Of Java

Java is also widely used by developers for developing Android apps. Let’s check the benefits of Java below:

  • It is a multi-threading language, it states that the program allows parallel execution of various parts of the program and makes the best use of the CPU. 
  • Java is object-oriented and simple to write code and develop modular programs. 
  • Moreover, Java is a platform-independent language and embraces the WORA (Write Once Run Anywhere) feature.
  • Java is as flexible as it’s required to move from one PC to another as it’s platform-independent language. 

Disadvantages Of Java

Now, let’s move on to the cons of Java:

  • In Java, unsigned char and unsigned int are not supported. Although, unsigned int and unsigned long APIs are available in Java 8. 
  • Java may become memory-consuming and lead to poor performance even compared to C and C++. That’s why Java demands the conversion to machine-level code.
  • In Java, GUI builders are still not mature and reliable. Popular frameworks, such as JavaFX, SWT, JSF, are used for building UI. It may make you invest more in research before choosing the right GUI builder. 
  • Java just targets storage despite data backup. 

Issues Of Java Got Resolution In Kotlin

Well, after learning about the disadvantages of Java, you might have understood that Java faces varied issues. Let’s check some with the resolutions in Kotlin. 

  • Null references in Java are controlled by the type system in Kotlin. 
  • There are no raw types.
  • In Kotlin, arrays are invariant. 
  • Kotlin comes with proper function types as compared to Java’s SAM-conversions. 
  • Kotlin uses site variance with no wildcards.
  • Kotlin doesn’t have checked exceptions. 

Kotlin or Java – Which To Choose For Mobile App Development?

After knowing about Kotlin and Java, their pros and cons, and past stories, it’s time to decide which one is the best for developing an app. So, let’s start:

A new and statically typed programming language, Kotlin was developed by JetBrains. It’s best suitable for building server-side apps, allowing users to write concise code as compared to Java, permitting app developers to resolve the same issues with fewer lines of code. 

Kotlin improves code readability and maintainability that means developers can read, write and change code efficiently. 

While considering the benefits of Kotlin vs. Java, the developers can use Kotlin easily for almost anything where Java is preferred, including client, server, web apps, and for building Android apps. 

Targeting benefits of Kotlin, there are some more reasons to choose Kotlin before Java:

  • Smarter and Safer Compiler
  • Type Inference
  • Easier to Maintain
  • Less code
  • Boost Productivity
  • Eliminating Null References
  • Safer Code
  • Data Classes

Business Benefits Of Kotlin

Let’s separate the benefits of Kotlin when preferred in businesses. 

  • Businesses pick Kotlin for any development, embracing client-based, server, Android, or web. 
  • Kotlin adoption is a shallow risk because of its interoperability with Java. 
  • Kotlin is a mix of procedural and functional programming.
  • When differentiating between Kotlin and Java, the former language holds a strong customer service team with a robust reputation. So, there’s no downtime. 
  • Kotlin has the caliber to resolve more issues with fewer lines of code. Its concise nature permits developers to read and alter code more efficiently to lower down a project’s time-to-market.
  • The learning curve and code review of Kotlin are easy, and developers find it easy to learn. 

The Future Of Java Programming Language

In this 21st century, if the developers are looking to build an enterprise solution, the name of Java is recalled as the market leader. 

In 2021, almost 35.35% of developers use Java and if not Java, they prefer picking one the JVM language, such as COBOL. 

In fact, the tech giants, such as Amazon, Google, and Microsoft are still working with Java to simplify their software development process. 

Future Of Kotlin

Well, while talking about Kotlin, we can say its future is bright. Its impact on the IT sector has grown exponentially in the last few years. 

Even the big web portals, such as Flipboard, Pinterest, or Basecamp are using Kolin previously also as is supported by the chief frameworks. 

As per the recent reports by Google, Kotlin is going to shine brighter and holds the caliber to challenge Java.

Is Kotlin Replacing Java? 

Well, many people are having questions like will Kotlin replace Java, and more like this. We will know what’s the right answer to such queries. 

As we can witness, everything is moving towards Kotlin. Although, Java still holds a lot of value and can’t be neglected. 

Java is still holding its place when it comes to general-programming language. Even for Android development, it’s believed to be a perfect language and is completely understandable. That’s why it’s picked the most by the developers.

Also, it depends on the development team also, with which language they feel comfortable working. 

These are valid concerns, also Java has been a widely known language for years. 

So, the chances of replacement are low right now. 

Kotlin vs. Java – A Quick Recap 

Parameters Kotlin Java
Invariant ArrayYes No
Lambda ExpressionYesNo
CompilationBytecodes Virtual Machine
Wildcard TypesNoYes
Smart CastsYes No
Null SafetyYesNo
Singletons ObjectsYesYes


Consequently, the debate over which programming language is better is not that simple and is likely to result in deep and exciting discussions.

Furthermore, there are various aspects that one should consider to understand the difference between these two. 

In this post, we have discussed almost every detail that will help you choose a suitable programming language for developing your app. 

In case, if you are still confused about which one to pick, you can hire an app development company. It will guide you on how to pick the best and suitable programming language for Android app development

FAQs Of Kotlin vs. Java

Is Kotlin The Same As Java?

No, Kotlin and Java are different from each other in various factors, like performance and speed. 
Java is a faster programming language as compared to Kotlin. 

What Is Kotlin Good For?

Kotlin is best for many things, such as unchecked exceptions, null safety, smart casts, property access, and lazy loading. Furthermore, various other smart features of Kotlin are there that make it the best programming language. 

Is Kotlin Better Than Java?

When we compare Java and Kotlin, choosing the one that’s better for app development is quite difficult. But, many developers pick Kotlin because of its documentation, its code’s implementation is quite simple. 
Even Kotlin is quite better than Java code when it comes to compatibility, security, syntax, type inference, boilerplate code, data classes, and functional programming. 
Simultaneously, various features of both the programming languages are similar, such as type system, lambda expressions, and annotation processing. 

Should I learn Java before Kotlin?

If you are new to the programming languages and the developer community, then of course, first you should Java code as Android code is still written using Java. 
Java is an object-oriented programming language. After you understand its basics, you can switch to Kotlin code. 
If you are an experienced developer, you can kick start with Kotlin’s course that makes you learn everything that you want to know. 

Is Kotlin good for web development?

Yes, why not! You can use Kotlin for developing apps. 
You can use Kotlin for back-systems instead of JavaScript. 
In brief, Lotlin is a full-stack solution that you can use in the browser, on the server, and on mobile.

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CTO at Emizentech and a member of the Forbes technology council, Amit Samsukha, is acknowledged by the Indian tech world as an innovator and community builder. He has a well-established vocation with 12+ years of progressive experience in the technology industry. He directs all product initiatives, worldwide sales and marketing, and business enablement. He has spearheaded the journey in the e-commerce landscape for various businesses in India and the U.S.