Kotlin vs Java: Which is Better for Android Development?

When Google declared Android a Kotlin‑first platform in 2019, it sent a clear signal to the mobile ecosystem: Kotlin had become a priority. That doesn’t mean Java is obsolete. Each language brings its own strengths and tradeoffs, and the “right” choice depends on business context and roadmap demands.

So, which one should you choose? Should you follow Google’s advice and pick Kotlin? Or should you go with a tried-and-proven language like Java?

Below, I’ll lay out a decision framework, rather than advocate for one side. Then you can match it to your product strategy, team, and risk profile. For most teams, the choice comes down to a few factors: existing codebase, team skills, hiring market, interoperability needs, and long-term Android roadmap.

Side‑by‑Side: Kotlin vs. Java

Kotlin: A Modern Programming Language for Pragmatic Teams

When Google introduced Kotlin, its intentions were clear – they wanted to provide developers with a more practical and efficient programming language for Android development services. Though Java was the right choice for developing applications, Google felt it needed some more modern features and better performance.

Google’s push for Kotlin surely affected the mobile development community. Since the Kotlin-first announcement, Google has been working on all of its Android apps with it. Big companies like Twitter, Netflix, Airbnb, and Pinterest have all switched to Kotlin. And many other developers are looking into it to make a move, charmed by the possibilities brought by the newest kid in the neighborhood.

Kotlin brings solutions to common issues and improvements to the Java programming experience as a whole. Some of them include:

• Interoperability. Kotlin was born out of a clear goal: to become a dominant language that would eventually sip into all platforms. That focus led its creators to provide Kotlin with high interoperability that allows you to use a vast amount of libraries and write modules that will work seamlessly with Java code.
• Code Economy. Java isn’t precisely known for being concise, something that Kotlin addresses full-on by offering a concise and readable syntax. It allows you to develop your Android projects faster while also reducing the likelihood of errors, especially in applications with a broad scope, an increased number of features, or high complexity. Kotlin’s emphasis on concise code and reduced boilerplate makes it easier to maintain and read compared to Java.
• Modern Programming Capabilities. Since Kotlin is so new, it was built on top of more modern approaches to programming. That means you can use fresh programming concepts for your development, including extension functions, high-order functions, delegates, and other options to build APIs. Kotlin supports operator overloading, making code more natural and expressive when working with custom types, a feature often called operator overloading Kotlin. Structured concurrency in Kotlin also helps manage asynchronous tasks in a predictable and organized way.
• Data Classes and Constructors. Kotlin simplifies data management with data classes, which automatically generate methods like getters, setters, equals(), hashCode(), and toString(). You can define a data class using a primary constructor, and Kotlin allows default values for constructor parameters, reducing boilerplate. For example, data class Person(val name: String, val age: Int = 30) uses a primary constructor with a default value for val age, making the code concise and easy to maintain.
• No Raw Types: There was a time when everybody was using raw types but as generics started to pop up, they were kept around to ensure backward compatibility. However, developers know that raw types can cause issues during execution. To cut that problem from the root, Kotlin doesn’t allow raw types, which leads to more type-safe code. Kotlin’s type system, along with features like data classes and primary constructors, contributes to concise and safe code.
• No Checked Exceptions. Certain Java developers might point out that checked exceptions are useful to perform error handling. However, these exceptions often cause empty catch blocks, which leads to developers losing time identifying the exception that caused it in the first place. Kotlin deals with this problem by removing checked exceptions altogether.
• Non-nullable Variables. One of the most well-known problems during Android development is NullPointerException. Kotlin deals with it by building null safety that prevents variables from taking a null value. Naturally, there’s a workaround for cases when a variable needs to have a null value, but, on a general level, the language doesn’t allow it.

All of those benefits might have you believe that Kotlin is better than Java, and that’s that. Yet, it’s better to outline Kotlin’s limitations and cons to provide you with a full picture. Some of the language drawbacks include:

• Steep Learning Curve. This might seem contradictory. How can a language that’s concise and highly readable be hard to learn? Yet, that brevity can be hard to grasp for developers used to other languages. Learning Kotlin requires a shift in how we think.
• Slow Compilation Speed. When compared to Java, Kotlin’s compilation is slower in most cases. You might find some projects where Kotlin beats Java speed, but that’s more like an exception than a rule.
• Boilerplate Code. Since Kotlin is a highly declarative language, it often tends to create boilerplate code in the corresponding JVM bytecode, leading to a verbose code that doesn’t need to be that way.
• Small Community. While Kotlin’s ecosystem is mature and growing, it’s still smaller than Java’s decades-old ecosystem in terms of libraries, tools, and community content.

Java: Mature, Ubiquitous, and Battle-Tested

Java is a developer favorite, especially in Android app development. That has a simple reason: Android used to be written in Java. However, since Kotlin’s introduction, many developers are questioning how useful it can genuinely be to stick to it when building Android apps.

The answer, again, might seem simple: just ditch Java and adopt Kotlin. Yet, there are plenty of reasons why Java has passed the test of time. Being one of the most popular programming languages around, it’s only natural that some want to stick with it without even considering an alternative.

Here’s why teams still choose Java:

• Easy to learn. Java is straightforward to learn, write, and understand. There are many resources available online to help you with training, but the syntax also presents ease of use and comprehension that make any Java project simple.
• Portability. Thanks to the Java Virtual Machine, Java is platform-independent, which means it can run virtually anywhere. This means that anything you develop with it might be ported easily to other platforms. Java also benefits from extensive libraries, supporting a wide range of applications from enterprise systems to Android apps.
• Legacy Android projects. Android might be choosing Kotlin as its go-to language, but that doesn’t mean it has cut its ties with Java. The Android SDK still contains many standard Java libraries, making it easier for Java developers to work on Android.
• More compact apps. Java apps tend to be more compact and far more optimizable. That’s a great thing when you want to create a new version of an app that’s desperately calling for better performance. What’s more – you can achieve that with lighter apps, thanks to Java’s imperative nature. Java uses primitive types (such as int, byte, short, double, float, boolean, char, and long), which are stored directly in memory and are more efficient than objects. In contrast, Kotlin treats all types as objects, which can impact memory usage.
• Static members and entry point. Java supports static members, which are shared across all instances of a class. The entry point of any Java application is the public static void main method, which is essential for program execution.
• Generics and wildcard types. Java supports generics with wildcard types (such as ?, ? extends T, and ? super T), allowing for flexible and type-safe collections and APIs.
• Large community. You’ll find issues when programming with any language. That’s a fact. So, it’s great for Java development teams to have a large community of experts supporting them. If you use Java and run into an issue, chances are you can find help online to solve it.

As you can see, there are plenty of benefits of working with Java in Android, even if Kotlin feels more tailor-made. Naturally, there are some drawbacks to Java, which you should consider before making a decision. Those cons include:

• Verbose. Java is a verbose language, which means you’ll have to write more code to power the same functionality that Kotlin would have with far less code. For one, there’s an increased risk of incurring errors and bugs. Then, there’s the possibility of bloating the application. Finally, there’s also an increased development time to get to the final product. Java’s lack of features like smart casts and operator overloading often results in more verbose code compared to Kotlin.
• Slow performance. Anyone who has used Java knows that it’s unfortunately slow, especially if you compare it to more modern languages – like Kotlin. That’s not all, as Java requires a lot of memory to perform correctly, which might be a dealbreaker to some.
• Absence of modern functions. Just as Kotlin is capable of using newer concepts and approaches to app development, the opposite is true for Java. Though we’re now seeing more and more updates for it, Java still feels like an old language in certain aspects, which can be challenging for new developers with a different approach to development. However, recent Java versions have introduced features like virtual threads for asynchronous programming, string templates (as a preview feature in JDK 21), and improvements to string literals, helping to modernize the language.

Null Safety and Error Handling: Avoiding the Billion-Dollar Mistake

Null pointer exceptions—long a pain point in Java—are a major source of crashes and hard-to-debug issues in backend and Android applications. Kotlin tackles this directly with built-in null safety.

In Kotlin, developers must explicitly declare whether a variable can hold a null value by using nullable types (e.g., String?) versus non-nullable types (e.g., String).

As a result, the compiler helps catch potential null pointer exceptions before your code ever runs, making your Android development process smoother and your applications more reliable.

Java, by contrast, allows any object to be null, leaving developers to rely on discipline and defensive coding. Without native null safety, bugs are more likely to slip through—especially in large codebases.

Kotlin also simplifies error handling. Features like smart casts, extension functions, and more concise try-catch blocks reduce boilerplate and improve readability.

For teams working in mixed Java/Kotlin codebases, Kotlin’s interoperability means you can adopt it gradually. You get the benefits of null safety without rewriting everything.

For Android and backend projects alike, Kotlin’s null safety and cleaner syntax lead to fewer bugs, less boilerplate, and more maintainable code.

Which One Should You Choose?

All of the above might feel like you’ll be forced to make the switch to Kotlin development services soon. This is not the case.

The key differences between Kotlin and Java—such as type inference, null safety, and concise syntax—should guide your decision. Java can do a great job in Android development and can be a perfect choice, especially in the hands of seasoned developers. When the time comes to make that language switch, Java development companies won’t have that much difficulty, as Kotlin is intertwined with Java in some sense.

The choice between Kotlin and Java often depends on project needs and developer experience. In many cases, Kotlin and Java can be used together, allowing teams to leverage the strengths of both languages. As a new language, Kotlin brings modern features and concise syntax to Android development, supporting contemporary programming paradigms.