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For years, Java has been the staple of Android development, but times change, and now Kotlin seems to be a new rising star. Some developers believe that Kotlin will soon replace Java completely, while others claim that Java is here to stay.
What’s the truth, and which programming language is better? In this article, our Java specialist compares Kotlin vs Java and discusses the pros and cons of both.
The difference between Java and Kotlin: a quick overview
Java was first introduced back in 1995, and since then, it has seen lots of changes and transformations. Now it’s among the top programming languages in the world and is suitable not only for web and mobile development but also for reactive programming and machine learning.
Kotlin, on the contrary, is a new kid on the block. In 2017, Google announced first-class support for this language during the “Google I/O,” and since then, the language skyrocketed in popularity. Many developers claim that Kotlin is a valid replacement for Java due to its functionality and interoperability. One of its biggest advantages is the fact that the language is suitable for JVMs and is 100% Java-interoperable.
Now, let’s look at both languages in a bit more detail.
What is Kotlin?
Kotlin is an open-source, statically typed language that is mostly used for Android development. One of its core features is interoperability with Java, meaning that developers can call into Java code from Kotlin (and the opposite) as well as use both Java and Kotlin code in their projects.
Kotlin was created in 2011 but it was officially released only in 2016. And just one year later, in 2017, Google announced its first-class support for Kotlin on Android. Since then, Kotlin has been gaining massive popularity and great support from the community.
The most notable features (that we’ll discuss in detail below) include:
- Interoperability
- Null safety
- Smart casts
- Coroutines
- Delegated properties
- Data classes
Before discussing what makes Kotlin superior to Java, it is important to to briefly review the latter.
What is Java?
Java is an object-oriented programming language that follows the Write Once, Run Anywhere (WORA) approach. Java is widely used not only for Android development but also for backend development and design of high-performing web applications.
Java’s first public implementation was released back in 1996 but since then, Java has not lost its popularity. Its constant evolution and huge community contribute to Java remaining among the top programming languages.
Some of the most interesting Java features that help it reman competitive are:
- Cross-platform compatibility
- Object-oriented programming
- Multithreading
- Distributed computing
- Architecture neutral
Now that we’ve answered the “what is Kotlin?” and “what is Java?” questions, let’s look at the Kotlin features that prove superior in comparison to Java functionality.
Benefits of Kotlin over Java
Now that we’ve briefly reviewed both languages, it’s time to move on to the next question. Why exactly do so many people believe that Kotlin is a new Android development standard if both languages have their pros and cons? Here are some of the biggest advantages of this language over Java.
No more null pointers
Named a billion-dollar mistake, the null pointer exceptions cost many companies lots of time and money as they attempted to fix these exceptions or avoid them in code.
With the Optional type boxing, Java tried to overcome this problem in its latest releases. But in my opinion, this just adds more complexity and more boilerplate code. It turns out that it might be easier to use the good old conditional null check.
Keeping this issue in mind, Kotlin was designed as a null-safe language. The language incorporated inherent null safety, which successfully prevented developers from fixing potential null-related issues. The only possible reasons for null pointer exceptions in Kotlin may be:
- An explicit call to throw NullPointerException(),
- Some data inconsistency related to initialization,
- Use of the !! operator.
No raw types
One more difference between Java and Kotlin is lack of raw types in the latter. The usage of raw types in Java can lead to spoiling type integrity of a collection and, therefore, to the occurrence of exceptions. Joshua Bloch, a former Google software engineer, even recommends not using raw types in code because of this issue.
Unlike Java, Kotlin doesn’t have raw types. The type of the collection should either be always defined explicitly (when passed as a parameter) or detected by a compiler when initialized.
Arrays are invariant
This is another problem with Java which can lead to spoiling the data integrity. The arrays in Java are designed to be covariant. So the following code is possible:
Integer[] myInts = {1,2,3,4};
Number[] myNumber = myInts;
What is wrong with that code? In fact, if we always use the Integer type we will be fine. But if we try putting some other type inside a collection we will have an ArrayStoreException during the runtime because the compiler doesn’t know the actual type of the variable.
myNumber[0] = 3.14; //attempt of heap pollution
In Kotlin arrays are invariant so the compiler will not allow such assignment.
No checked exceptions
The benefits of checked exceptions are a rather arguable topic. Take a look at this code:
Appendable append(CharSequence csq) throws IOException;
This exception is placed here because one of the implementations of the Appendable interface can use IO (the author implements Appendable as well). That means that for all other implementations of the append method (like StringBuilder, console, etc.) we should wrap this call with try {} catch {} block. The other way is to add throws IOException to each method signature in the call chain. This seems unnecessary and affects code readability in a bad way.
Kotlin doesn’t have checked exceptions and therefore you don’t need to add redundant try catch blocks and throws signatures.
Smart casts
In Java, you have to use the instance of operator and then explicitly cast type. Kotlin provides the is operator instead and the compiler casts objects automatically:
fun demo(x: Any) {
if (x is String) {
print(x.length) // x is automatically cast to String
}
}
Concise code
It goes without saying that brevity is a key to productivity. If we look at Java, the boilerplate code is still a big issue even though it tends to have a high level of readability. As for Kotlin, it combines brevity with readability and allows developers to write code in fewer lines if compared to Java.
Introduction of coroutines
To enable seamless functioning of the main thread while handling lengthy operations, Java allows the creation of multiple background threads. In this way, Java tried to facilitate the management of several threads without disrupting the work of the main one but this approach has several drawbacks. The biggest one is that management of multiple threads often causes errors and complications in the code, negatively affecting the app’s performance.
Kotlin took this feature further and introduced coroutines. Because they are stackless, developers can suspend the code execution and simply resume it later, whenever they need to. In this way, coroutines help avoid having too many threads while Java does not have such function. On top of that, coroutines are more concise and clear, which is also a big benefit.
Kotlin drawbacks for consideration
Even though Kotlin seems to be more efficient and high-performing than Java, it has certain drawbacks that are to be addressed. They are:
- Ambiguous compilation speed: many developers claim that they observed fluctuations in Kotlin code compilation speed. While it might be really fast, it might also be really slow so you can never know.
- No primitive types: Kotlin completely lacks the primitive types that Java has and that can guarantee memory footprint and better performance.
Java vs Kotling: functionality comparison
Both languages have rich functionality and are designed to help developers code in a faster and more efficient manner. At the same time, both languages have certain features that are not present in the other. Let’s have a closer look at Java vs Kotlin.
Java features that Kotlin does not have
Even though the list is not too long, it’s still worth mentioning:
- Primitive types
- Static members
- Wildcard types
- Non-private fields.
Kotlin features that Java does not have
As for Kotlin, the list of brand-new features will be longer:
- Inline functions
- Null safety
- String templates
- Singletons
- Smart casts
- Extension functions
- Range expressions
- Companion objects
- First-class delegation.
And that’s not even a full list.
The business benefits of deploying Kotlin
One more thing left to discuss is the way Kotlin benefit one’s business:
Faster development
Because Kotlin is known for its brevity, it requires less time for developers to write code and check it for bugs and errors. In addition, it has more concise and expressive syntax compared to Java. This makes Kotlin easier to read and understand, reduces boilerplate code greatly, and minimizes the number of errors in the code.
Higher-quality applications
No null pointers, fewer lines of code, and an array of features that ensure seamless performance – Kotlin takes really good care of the app’s quality. The minimal number of code lines also leaves less space for bugs and errors, which is a plus.
Cost-saving
First, Kotlin ensures robust and high-quality performance, which means saving money on debugging. Second, Kotlin is fully interoperable with Java so its integration does not mean you will need to revamp your whole ecosystem.
Community support
Community support is important for any programming language as it helps developers quicker resolve issues, find answers to their questions, and access useful documentation. Not to mention that the community is responsible for creating and maintaining an ecosystem of tools and libraries around the programming language, which is also highly important. Kotlin has both extensive community support and official support from Google, thus being a very developer-friendly language to use.
Versatility
Thpugh Kotlin is mostly associated with Android app development, it is not limited to it. Kotlin can also be used for web development and backend development – for the latter, we recommend using Ktor and Spring Boot frameworks.
Also, Kotlin is very scalable, thus being a great choice for enterprise-grade solutions. As your business grows, the language can grow together with it, adapting to your evolving needs.
When to choose Kotlin or Java: use cases
We’ve already figured out that, despite Kotlin’s popularity, Java remains highly relevant. The big question is what language to choose for your specific project? To help you with that, we’ve listed the main use cases for both Java and Kotlin.
Use Kotlin if:
- You need to develop a powerful and scalable Android application
- You need to enhance and optimize existing Java projects
Use Java if:
- You need a reliable tool for backend development
- You want to build an enterprise-grade system
- You build an app that calls for high backward compatibility
In short, Kotlin is a better choice for Android app development while Java is a solid option for backend and web development. But is Kotlin better than Java? Not entirely since they are quite different in specific aspects.
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Should you choose Kotlin or Java? Summing up
I’d say you should choose both. Java, without a doubt, is the backbone of thousands of flawless applications in dozens of domains, such as healthcare, education, e-commerce, or telemedicine. With the help of Java, developers can create responsive and user-friendly apps that will display a high level of quality and security.
On the other hand, Kotlin is a really hot trend and to be a good developer, one needs to be aware of modern trends. Even if you are not going to fully switch from Java to Kotlin or can’t decide between Kotlin vs Java, you might at least try to implement Kotlin partially and see how it turns out. Maybe you will become a Kotlin evangelist or stay loyal to Java – only practice and time can tell.
At SoftTeco, we have over 16 years of experience with Java development so we are confident in the Java products that we develop. However, we are also open to everything new so we will for sure introduce Kotlin to our projects and see what works best for a specific project.
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