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Java vs Kotlin: The Best Framework For Android App Development

A recent report published by Statista indicates that the number of smartphone users worldwide has crossed 3 billion and is forecasted to further grow by several hundred million in the next few years. We’re officially in the era of smartphones.

As a result of the growing smartphones market, the mobile app development market has become highly competitive, making it hard for developers to choose the right framework for their mobile apps.

Unfortunately, a one-size-fits-all or a one-size-fits-most approach is not the best one when it comes to choosing a framework for Android app development. This is because there is a sea of mobile frameworks available to serve multiple needs.

Java, Kotlin, React Native, Xamarin, Flutter, Corona SDK, and Ionic are some of the popular mobile app development frameworks.

Because of the overwhelming framework options that exist today, most businesses struggle to choose a framework that meets their specific project and business requirements.

There is no quick fix when it comes to Android app frameworks.

Of all the frameworks available, Java and Kotlin seem to rule the Android app development industry lately. This post compares these two frameworks for Android app development.

Lets’ begin with a small introduction to both the frameworks.

Java is one of the most well-known programming languages that has been in existence for 24 years. It tops the list of the most popular programming languages of all time. In fact, it is one of the most used frameworks by developers.

According to a recent Statista report, JavaScript and HTML/CSS were the most commonly used programming languages among software developers around the world, with nearly 68 percent of respondents stating that they used JavaScript and 63.5 percent using HTML/CSS. SQL. Python, and Java made it to the top five most widely used programming languages around the world.

Do you know why this popular programming language rules the enterprise programming language field?

Thanks to big tech giants like Google, eBay, and Amazon that are primarily using Java to build their Android mobile applications, it has become a ruling framework in the enterprise programming language realm.

How Java works:

Java is a platform-independent framework that works on the principle of ‘Write Once & Run Everywhere’.

It is concurrent, class-based, and object-oriented, meaning that it is easy for developers to attain fluency with this programming language. It requires executing an engine, compiler, and a set of libraries.

Believe it or not, most of the syntax used in this framework is derived from C & C++.

Kotlin is a general-purpose, modern programming language that introduces functional features to support Java interoperability. It aims for heightened productivity and improved coding experience.

Although Java has an undisputed reputation of being ahead than Kotlin and most other frameworks due to its long existence, there was a need for a newer framework that could fill the gaps that Java leaves.

Kotlin proved to be that modern app development framework which turned the tables.

Do you know that it is now the official language for Android apps? Google officially announced this big news at Google IO in May 2019.

A recent developer survey for Kotlin by JetBrains suggests that the framework is being targeted by developers most (the figure is 66%) for Android app development. It further indicates that Kotlin is used mainly for new projects (96%), and only 38% use it for pre-existing projects.

How Kotlin works:

Based on JVM, this modern, open-source framework is completely compatible with Java stacks. This concise programming language is a combination of object-oriented and functional programming features and can be used everywhere Java is used.

Java vs Kotlin in Android app development

Let’s compare the two popular frameworks on different parameters now:

1. Development speed- Developing a mobile app is an expensive process. One way to keep the costs down is to keep the app development time down. The faster the app development speed, the lower are the costs. Here’s a comparison of the development speed in Java vs Kotlin.

Java- If you choose Java, you will probably have to type more code than in Kotlin for the same task. But what’s important to note here is that you will have to spend less time thinking of the solution in this case than in Kotlin. Also, despite being a highly verbose language, it provides type safety which catches all potential errors at compile time rather than at runtime.

Kotlin- Although Kotlin has more cognitive load than Java, it requires typing fewer codes. Moreover, it has clean and intuitive syntax. But it would require you to spend more time thinking of the solution. It generates a byte-code that’s essentially the same as Java byte-code, meaning that there’s no measurable difference. It does not have any runtime semantics (over and above Java) or meta-programming, which means its performance is very close to that of Java. It has more laconic constructions which means you can control the coding speed by writing expressive codes.


It’s a draw.

Since both of them run on the Java Virtual Machine (JVM), it would be somewhat naive to say or ask which one of the two offers faster development. There’s no noticeable difference between the two frameworks in terms of the speed of coding. Both offer the same speed of development.

If you prefer to write more codes but spend less time thinking of the solution, Java is your best choice. And if you prefer to write fewer codes, while spending more time thinking about the solution (i.e you’re a fantastic abstract thinker), Kotlin is your best bet.

2. Community support- Imagine you face a problem while using either of the two frameworks for your Android app development. What do you do? Where do you go? Well, this is where community support comes into play. Let’s look at the community support in Java vs Kotlin for Android app development.

Java- It has a solid and active community support since it has existed for a long time. There are many online Java-related resources available to help Java programmers. Stack overflow, Oracle, and Java Ranch are some of the most popular Java communities that exist on the web, ensuring long-term support for the programming language. The Java developer community boasts in-depth information on Java technologies and aims to bring you up-to-date on any new development.

Kotlin- It doesn’t have very active community support when compared to Java. This is because the framework has been in existence only since February 2016. Yet, its global community is growing fast with its contributors increasing by every passing day. Though younger than Java, Kotlin has evolved into quite an established framework now. It further aims to become a rich ecosystem with an extensive range of community libraries soon.


In terms of community support, Java is clearly ahead of Kotlin, simply because it is an old framework that has existed for quite some time now. Kotlin, on the other hand, is a newer framework with a not-so-evolved community support.

3. Extension functions- These functions allow methods defined outside of a class to be used with objects of that class (using the ‘.’ notation) as if they are part of the class. Without them, adding functionality to a class isn’t possible without modifying the entire class. Let’s look at the extension functions in Java vs Kotlin for Android app development.

Java- Extension functions, although available in many other programming languages and frameworks, aren’t available in Java. Think about a class like String where adding functionality is necessary. Unfortunately, extending classes to add functionality by adding new methods is not possible in Java.

Kotlin- Unlike Java, Kotlin has extension functions which allows developers to extend a class with new functionality. It is easy to create an extension function in Kotlin. All you have to do is prefix the name of the class that needs to be extended to the name of the function being created. In order to call the function on the instances of the extended class, you will need to use the ‘.’ notation.


Is Kotlin better than Java? No.

It’s all about your personal preference.

If it’s crucial for you to be able to implement features in a way that enables you to reuse them without the need to implement complex functionality, then Kotlin is a better choice. Also, if it is necessary for you to add functionality to an existing class in a way that it doesn’t require you to modify the entire class, Kotlin is your best bet.

What Java Has That Kotlin Does NotWhat Kotlin Has That Java Does Not
Checked exceptionsLambda expressions and higher order functions
Primitive types that are not classesExtension functions
Static membersNull safety
Wildcard typesSmart casts
Ternary operation a?b:cStrong templates
Faster compilation speedPrimary constructors
Unlimited resourcesFirst-class delegation
Faster auto-complete featuresSingletons
Wide open-source ecosystemRange expressions
Faster build processOperator overloading
Accelerated assembly with GradleCompanion objects
Data classes

Java vs Kotlin for Android app development: Pros and Cons

Pros of JavaCons of JavaPros of KotlinCons of Kotlin
Ease of learningMore chances of errors and bugsFewer errors and bugsSteep learning curve
Works well for both Native and cross-platform appsExperiences inherent limitationsSeamless transition from Java to KotlinDifficult to find experienced developers
Plenty of Java librariesProblems with Android API designAids in the building of clean APIsSome features of Android Studio tend to rub slower
Wide open-source ecosystemAbsence of null in its type systemHas null in its type system
Lighter, more compact appsRequires more memory, hence it tends to be slowerAn active Anko library for developersLimited learning resources (The community still being young)
Faster build processType-heavy languageHighly-concise codes; faster to typeSlower compilation speed

Still confused?

If you do not want to miss out on the advantages of either of the two frameworks (discussed above) for Android app development, there’s a way around.

You can use the two frameworks interchangeably to get the best of both worlds.


You have the flexibility to use them simultaneously in your Android app development project by calling Java code from Kotlin and vice-versa since both frameworks compile to bytecode in the end.

Although there are several differences between the two programming languages in terms of stability, community support, null value, code conciseness, and extension functions, among others, they are fully interoperable.

As a leading provider of mobile app development services, Jellyfish Technologies knows the trade-offs of each framework and can help you select one that will meet your business needs in the best possible way.

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