31 January 2025
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Android is one of the most popular mobile platforms in the world. The technology is behind millions of apps, ranging from various utilities to world-spanning products. An important aspect when developing an Android app is choosing the programming language. This decision may affect how quickly you build, how easily the code can be handled, and how seamlessly the app works.
When we compare Kotlin vs Java, Java was the world’s primary language for making Android applications for many years. It is stable and reliable, and has high utilisation. However, in recent years, Kotlin has attracted much attention. In fact, Google also recommends using Kotlin, a preferred language for Android apps.
Therefore, which one should you pick, Kotlin or Java? That is what this blog aims to help with . We shall analyse the strengths and weaknesses of Android Java vs Kotlin. You can get a better idea of what works for you, post this!
Let’s understand both Kotlin vs Java, briefly:
Java is a relatively old programming language developed in the mid-90s. It is one of the most popular languages worldwide. When Android was released in 2008, Java became an official language for building Android apps.
It is known to be stable, reliable, and easy to scale. Many Android apps today are still coded in Java, but on a massive scale. It also boasts a vast support community and mountains of libraries and frameworks.
If you have worked with Android apps before, you have probably used Java. It’s still common in many companies who are comparing Java vs Kotlin Android, especially those with legacy codebases.
Kotlin is a modern programming language created by JetBrains (the group that makes IntelliJ IDEA, which drives Android Studio). It was launched in 2011 but became quite popular in 2017, specifically when Google announced its support for it in Android development.
Kotlin has been designed to be modern and developer-oriented. It solves some of Java’s frequent pain points, including lengthy, repetitive code and null pointer exceptions. With Kotlin, you can write cleaner and shorter, easier code to maintain.
Yes, absolutely. Kotlin vs Java are both used in developing Android applications nowadays. Google has concluded that Kotlin is the best choice, but it has not completely replaced Java.
Many apps are still being developed on Java, and new projects are usually initiated in Kotlin. The two languages are commonly seen in the same Android project. They work well together, allowing developers flexibility and choice.
Let’s unravel the main differences between Kotlin vs Java to give you a clear picture of what makes them different.
When comparing Java and Kotlin, one of the first things you will notice is the visual difference in the code.
Java is usually verbose. In most cases, you have to write many more lines of code to make things happen. It’s not always bad, though, as it’s organized and familiar to many developers. But it may feel bulky, especially with small tasks.
Kotlin, on the contrary, has a clean, to-the-point syntax. Not having many lines allows you to get the desired results. This not only makes the code more readable but also minimizes the likelihood of making mistakes. Developers claim the Kotlin code seems more modern and natural, especially for novices.
Null pointer exceptions (NPEs) are one of the most frequent causes of app crashes. Java has no built-in security from them. You may get a NullPointerException if you attempt to use a non-initialised variable.
Kotlin handles this problem differently. It has null safety that is baked into the language. You are required to declare explicitly whether or not a variable can be null. In this manner, many potential bugs are identified at compile time instead of at runtime.
Java and Kotlin can perform background functions that are vital to Android development. Imagine loading data from the internet, images, or computing without freezing the app’s screen.
Java uses threads and executors. It works, but keeping track of multiple threads is not easy. Proper threading usually requires writing massive amounts of boilerplate code.
Kotlin uses coroutines, and that’s when things become much simpler. Coroutines ensure that asynchronous code looks and feels like standard sequential code. This makes maintenance easier for you when reading the code. You don’t have to be too concerned about callbacks and handling various threads.
Another convenient function of Kotlin is extension functions. These enable you to introduce new functionality to existing classes without inheriting from the classes or altering their source code.
If you want to inject a new method into some standard Android class, such as TextView. In Java, you must make a utility class or inherit from an existing one. However, in Kotlin, you can declare an extension function, which seems to belong to the initial class.
This makes the code readable and reusable. It also helps organize the code, mainly in large projects.
Java has been in the market for a long time. It has a massive developer community and many libraries, tools, and frameworks. If you encounter an issue, there is a greater chance that someone has already faced it, and you will find numerous solutions online.
As Kotlin is new, it has a smaller community. However, it is rapidly improving, especially after Google officially supported it in 2017. More and more libraries have been supporting Kotlin, and many modern Android libraries have been developed to be used with Kotlin.
The good news is that Kotlin is completely interoperable with Java. You can use Java libraries in your Kotlin code and vice versa. Although Kotlin’s ecosystem is not as big right now, you are not deprived of anything.
Kotlin vs Java performance concerns will always be present, especially for huge or resource-intensive apps.
In practice, Kotlin and Java provide nearly identical runtime performance. Both can be compiled into bytecodes on the Java Virtual Machine (JVM). However, Kotlin’s features, such as extension functions and lambdas, may cause a little overhead.
Java almost always compiles faster than Kotlin when it comes to compile time. However, Kotlin is improving with each new release. Most Kotlin for Java developers working on everyday apps, the difference in speed won’t matter daily.
If you are not deploying extremely performance-critical apps, both of the languages should prove helpful to you.
Kotlin is safer, more modern, and concise. Java is a stable and well-supported programming language. If you are beginning from scratch or want a more pleasant coding experience, this often involves Kotlin. However, staying with Java can still make tremendous sense if you’re dealing with an older code base or already working with a Java team.
| Feature | Java | Kotlin |
|---|---|---|
| Year of Release | 1995 | 2011 |
| Official Android Support | Yes (since 2008) | Yes (official support since 2017) |
| Syntax | Verbose, more boilerplate | Concise and expressive |
| Null Safety | No built-in null safety | Built-in null safety reduces crashes |
| Coroutines vs Threads | Uses threads and callbacks | Uses coroutines for easier async code |
| Extension Functions | Not supported | Supported, adds functionality without inheritance |
| Community Size | Larger, older ecosystem | Growing fast, strong Google support |
| Library Support | Huge library base | Interoperable with Java libraries |
| Performance (Runtime) | Very fast, highly optimized | Comparable to Java, slight overhead in some cases |
| Learning Curve | Easier for beginners (more tutorials available) | Slightly steeper, but more modern and beginner-friendly |
| Code Interoperability | Java only | Can mix with Java easily |
| Preferred by Google? | No longer preferred | Yes, now the recommended language for Android |
Kotlin has gained popularity, and nowadays, it is the top language for developing an Android application, especially after Google officially supported it. However, like any other tool, it also has its own set of advantages and disadvantages. Let’s look closely at both options to help you decide whether they are right for your app or project.
Kotlin makes you do more with less code. What will take several lines in Java can be accomplished in a few lines in Kotlin. This makes the code less wordy, easier to maintain, and faster to code. This means fewer bugs and increased speed of development for teams.
Kotlin is designed for modern developers. It has valuable features such as brilliant casts, type inference, lambda expressions, and extension functions. These modern tools help make your code more flexible and powerful while not contributing to its harder readability.
The most significant benefit of Kotlin is its built-in null safety that is inbuilt. It prevents null pointer exceptions that cause crashes in Android apps. With Kotlin, variables are nullable or non-nullable by default, leaving you with fewer issues in the code, as they can be identified at compile time.
Google has officially supported Kotlin for Android development since 2017. Notably, it has become Google’s choice of language for Android nowadays. This has improved integration with Android Studio, provided more documentation, and provided more updates for Kotlin users.
Kotlin works smoothly with Java. Calling Java code from Kotlin and vice versa without any special setup is possible. This makes it easy to transfer projects from Java to Kotlin or use the two languages in one project.
Kotlin is easier in the long run, but things can be tricky initially, especially if you have been working with Java. New developers may feel lost regarding ideas such as coroutines, higher-order functions, and extension functions. If your team is unfamiliar with Kotlin and uses it for the first time, then there will be a learning curve when you get used to it.
Kotlin is slower than Java at compilation in some cases. Although Kotlin’s runtime performance is almost equal to Java’s, its compile time, particularly annotation processing, lags. This may be a problem only for bigger projects, but the gap is typically small.
Kotlin is still growing. Although it has gained popularity relatively quickly, it has a smaller community than Java. Java has been in the market for more than two decades; therefore, there are many developers, more Stack Overflow answers, and a larger number of third-party tools. Kotlin is quickly gaining popularity, but at some point, you may realize you don’t find enough help on the Internet.
Kotlin is a new programming language; therefore, there are not as many tutorials, courses, or forums for it as there are for the old one, Java. The official documentation is not inadequate, but teen-friendly guides are more challenging to locate. Java will probably seem less challenging to learn from the ground up if you start learning Android development due to the amount of information available on the subject.
Java has been the foundation of Android since its inception. It is a general language with the ability to apply objects, and it’s known for its reliability and vast industry applications. In fact, a large number of Android apps were and are still being developed or managed using Java today.
Java has existed since the mid-90s. That is to say, it has had years to develop, perfect, and find its feet as a reliable, stable language. It has been used in millions of apps, websites, tools, and systems, so it has stood the test of time. People trust it because it is reliable.
From day one, Java has been the prevailing language for Android. Many apps on the Play Store are in Java or use Java code heavily.
One of Java’s most significant advantages is its massive ecosystem. There are thousands of libraries, tools, and frameworks. If you’re creating something, there is a Java library available to assist you.
This is also the case with Android development. Java covers all major libraries, from networking to loading images to databases.
Due to its long use, Java has one of the largest developer communities worldwide. There are heaps of online tutorials, guides, blogs, and Q&A forums. Getting stuck? Chances are that someone else has had the same problem and the solution, too.
This is an excellent addition for starters. The learning curve becomes less rocky when help is merely at the other end of a speedy surf on Google.
Java’s runtime is still excellent. There are situations when Java apps will build and execute faster than Kotlin ones, especially if you don’t use features like annotation processing or reflection. It may not be obvious, but for huge apps, performance still counts.
There are many repetitions in Java code, and it is usually long. You’ll write boilerplate code to do basic things, such as setting getters/setters, defining constructors, implementing listeners, etc. With time, this may make your code hard to read and maintain.
Java can get clunky and old-fashioned compared to Kotlin, which is much shorter.
There is no null safety within Java. In other words, one can inadvertently over-assign a null value where they shouldn’t, but the app won’t complain until it blows up. This is one of the most frequent Java-based Android apps where bugs and crashes occur.
Although you can minimize this issue by writing more checks or utilising Optional and other such tools, you have to handle it manually. Kotlin, by comparison, handles this much better right out of the box.
Since Java is old and widely used, alterations to its language creep in gradually, and new features are implemented. Although this makes it more stable, it also explains why Java always lags behind more modern languages, such as Kotlin, in innovation.
From the beginning, Kotlin featured such things as lambda expressions and streams, whereas Java introduced them only recently. When comparing Kotlin vs Java for Android, you may find Java a tad restrictive if you like modern, expressive code.
While Java is still fully supported for Android, Google recommends Kotlin as the default language. Most new Android tools and libraries are being developed using Kotlin, and tutorials follow this movement. Java is not outdated; however, it is no longer at the forefront of Android.
Kotlin was a language of choice for many Android developers, but not all projects are suitable for it. When can you use Kotlin, when comparing Java vs Kotlin? Now, let’s consider a few of the ideal situations in which Kotlin excels. Wondering to hire Android Developers get in touch with Dev Story now!
Kotlin can be the best option for starting a new Android project from scratch. It is also constructed with modern development in mind, providing a more succinct and terse syntax than Java. This means you can do the same things with a smaller amount of code. To developers, this means faster development times and easier-to-maintain, cleaner code.
If you do not work with a large team or in agile mode, then Kotlin can be a game changer. Thanks to the short syntax and high-level features, development cycles are shortened, making it crucial if you are required to build and iterate fast. Its compatibility with Java is seamless; therefore, if you have to incorporate Kotlin into a project based on the Java language, that won’t be a problem.
One of Kotlin’s advantages over Java is that it can prevent common errors in code, especially when it comes to null pointer exceptions, which are notorious when Kotlin’s null safety feature comes at no extra cost to the developer since it does not require developers to subscribe to it. On the contrary, Kotlin’s null safety feature is built-in, meaning null-related errors detected at runtime are caught during compilation, resulting in fewer crashes in production.
Since Google formally backed Kotlin as the first choice of language for developing Android, it has gained significant traction and is now the common pick. Most new Android tools, libraries, and SDKs have been optimized for Kotlin. The Android community has maintained this trend as it concentrates more on Kotlin development. Therefore, Kotlin will be the best way to keep up with the trends and best practices on Android apps.
Kotlin makes your code more elegant and allows you to be more productive. Features such as data classes, default arguments, and extension functions allow developers to do more with less code. This enables them to create apps at a faster pace and with reduced bugs, allowing the teams to stay on schedule.
The compactness of Kotlin syntax also makes the code you are working on easier to manage. For teams working on a long-term project, having clean and organized code is very beneficial, as this can save you a lot of time when updating or fixing bugs.
While Kotlin is the rising star in Android development, Java isn’t going anywhere. In specific situations, sticking with Java is still the best choice for your project. Here are some scenarios where Java remains a solid, reliable option.
If you are dealing with an existing project entirely based on Java, it will often be prudent to use it for further development. Rewriting a large codebase into Kotlin may seem tempting, but it can also cause unnecessary risks, delays, and expenses. The Kotlin migration from Java consumes much time, as good planning is required to avoid functionality breaking, and it is laborious.
If your team is already excellent at using Java, it might be wiser to keep using it in the short run. Learning Kotlin’s syntax and its features might require time, and it can temporarily slow down your development process. If your team is accustomed to how Java does things, switching might result in a learning curve and lower production in the initial stages.
Java’s ecosystem and community are huge, so if your team is familiar with them, they will be able to solve problems quickly and effectively. In addition, many resources are available, which makes it easier for experienced Java developers to overcome the challenges that may arise.
Now let’s talk about Java vs Kotlin performance. Java provides better control over optimizations when you compare Java vs Kotlin, in certain situations. For instance, if an app requires performance, real-time apps, games, or when resources are limited, Java can be more appropriate.
You may be wondering, is Kotlin similar to Java in performance? Although Kotlin’s performance is similar to Java’s, in some instances, Java provides developers with finer control over memory management and execution. If you need to tweak your app’s performance fine-grained, Java’s older and more solid tools and practices might provide the room you need.
Java has existed for decades, and developers have gained a lot from its performance nuances. In regions where micro-optimizations are of great importance, between Java vs Kotlin, Java could remain the better tool for the job.
Although Kotlin has 100% interoperability with Java and similar libraries with Java in most cases, some old and niche libraries might not support Java. If you rely on a set of third-party tools that are very much Java-focused, you may spare yourself the trouble of making sure you can interoperate with Kotlin if you stick to Java.
Java is an old language; therefore, a wide range of established libraries, APIs, and tools exist for almost any use-case scenario. This is especially true in a legacy industry or an enterprise environment where stability and backward compatibility are critical.
Java is ubiquitous when it comes to supporting older Android versions. While Kotlin targets Android API levels 16 and above, Java has been supported since its inception and is more compatible with legacy systems. If your app requires supporting users in older versions of Android or if it needs to be backward compatible, Java might offer fewer headaches.
Now, Kotlin is rapidly gaining the position of the most popular and best language for developing Android apps. Big companies such as Google, Pinterest, and Uber, among others, are actively switching to Kotlin because of its modern features, simplicity, and efficiency. When we talk about Java vs Kotlin, the growth of Kotlin has received a further boost from Google’s official endorsement as the preferred language for Android development.
Based on job listings and industry statistics, Kotlin is highly sought after. Given the increasing popularity of such demand, we can only imagine how many Android developer positions actually require expertise in Kotlin. But Java still occupies a strong position, particularly in organizations with legacy arrays of code or for large existing groups of programmers.
Generally, Kotlin’s rise can be seen in the market, with more developers and companies switching to this technology for new projects. However, Java is still relevant, particularly for teams accustomed to it or developing so-called legacy applications. The trend indicates that Kotlin is the future, but Java still has an essential position in the present.
To conclude, both Kotlin and Java offer distinct advantages and are widely used in Android app development services. Kotlin stands out for its modern features like concise syntax, null safety, and seamless integration with Android development tools, making it an ideal choice for new projects, smaller teams, or developers aiming for clean and secure code.
On the other hand, Java remains a reliable option for legacy codebases, experienced developers, and high-performance applications where its maturity and robust ecosystem are key factors.
However, there is no one-size-fits-all solution when it comes to choosing between Java and Kotlin. The best choice depends on the specific needs of your project, your team’s expertise, and your long-term objectives. If you’re building a new Android app and focusing on efficiency and modern features, Kotlin is a fantastic option.
