Kotlin vs Java: What is the Best Choice?

In the world of software development, selecting the most appropriate programming language is probably the most critical decision you will make. For many years now, Java has reigned supreme in enterprise applications and Android development due to its stability and extensive ecosystem. Then in 2016, Kotlin arrived as a newer, more concise, and developer-friendly alternative.

Now the question remains, which one is, in fact, the right one for your next project? In this blog post, we will examine both of these robust languages on a series of technical considerations and assist seasoned developers in finding an accurate option.

Origin of Kotlin

Kotlin is a programming language created by JetBrains in 2011. In 2017, Google began officially supporting Kotlin as an Android development language. Modern, concise, and interoperable with Java, Kotlin was developed to address the limitations of the Java language.

It is designed to improve the syntax and null safety of code while also increasing the productivity of developers. In 2019, Google declared Kotlin the primary language for developing Android applications.

Origin of Java

Java is a popular, object-oriented programming language known for its portability and robustness. Since its introduction to the development community in 1995, Java has continued to be a foundation for Android development, ultimately powering millions of apps on Google Play due to its "write once, run anywhere" approach. With Java's extensive ecosystem of libraries and frameworks, it has proven to be an excellent choice for applications intended for enterprise use.

Kotlin vs Java: Key Differences to Note 

Explore how Kotlin and Java differ in their design, performance, and safety features, helping you select the right fit for your project needs. 

Syntax and Readability

Java's syntax is considered verbose, meaning that it will require more code in order to accomplish even simple tasks. For example, consider declaring a variable in Java:

String name = John Doe

In addition to this, there often exists a fair amount of boilerplate code (e.g., getters and setters, etc.) that makes our Java code much longer overall. 

With Kotlin's more concise syntax, less boilerplate code is often necessary, which strengthens code readability as well. 

For Example, here is that same variable being declared in Kotlin:

val name = John Doe

Finally, certain features of Kotlin, such as data classes, will automatically create getters, setters, and many other utilities that can save us time.

Null Safety 

One of Kotlin's most significant advantages is its integrated null safety. Java lets you, by default, assign variables an initial value of null. This defect leads to the dreaded NullPointerException, otherwise known as "the billion-dollar mistake." Kotlin handles this by providing that all variables are non-null by default, meaning that developers are required to explicitly handle the null case.

In Kotlin, you must use the nullable type operator (?) to allow the null value, and rely on your compiler to make sure you're handling null cases at run-time. Based on Google's internal data, Kotlin's null safety system can reduce null pointer exceptions by as much as 20%.

Programming Paradigms 

Java is strictly an object-oriented programming language. In contrast, Kotlin can be either object-oriented or functional, providing developers with the flexibility to select the programming style suitable for their use case. This also allows for more expressive code, utilizing features such as lambda expressions, higher-order functions, and extension functions.

Concurrent and Threading 

Another key distinction between the two languages is in their approach to concurrent programming. Java uses multithreading, which presents an opportunity for complexity and errors associated with making it challenging to manage threads with multithreading. Kotlin consists of coroutines that are lightweight threads and allow for asynchronous programming.

Coroutines offer clean, simple writing of asynchronous code that can read like it is synchronous, which creates opportunities for easier debugging and readability. Coroutines are a compelling contribution because they enable the developer to progress when concurrent operations are in use without waking and sleeping, potentially when blocking on the main thread, which is a consideration with Android App development.

Learning Curve 

Java's lengthy syntax and complex concepts (such as checked exceptions) can be overwhelming to newcomers. Nonetheless, its popularity means many of learning resources.

Kotlin is easier to learn, especially if you've previously learned Java, because of its more intuitive syntax. Any modern features (e.g., lambda expressions) will contribute to its desirability to a new developer. It also proffers plenty of libraries for Android development, making your job a way easier. 

Interoperability 

Java and Kotlin are entirely compatible, meaning developers can use both languages within the same app. It functions completely with current Java libraries and frameworks. Meanwhile, Kotlin is developed to be fully compatible with Java, so existing projects can migrate to the Kotlin language incrementally. Kotlin can call Java in a Kotlin file, and Java can call Kotlin in a Java file with no trouble.

Community and Ecosystem 

Java boasts a huge and well-established community made up of more than 12 million developers around the globe. This large base provides plenty of documentation, useful libraries, reliable frameworks, and accessible learning tools.

Kotlin is gaining popularity fast and now has about 5.3 million developers, with 2.5 million joining in just the past two years. Kotlin’s community is smaller than Java’s, but it gets solid support from JetBrains and Google.

Kotlin vs Java: Performance Comparison

Here is the table comparing Java and Kotlin performance, highlighting benchmarks and insights from current industry aspects. 

Performance Aspect	Java	Kotlin
Compilation Speed	Faster for clean builds; highly optimized and mature	Slightly slower for clean builds due to advanced features
Incremental Builds	Consistently fast, but Kotlin often matches in practice	Matches or exceeds Java during incremental builds
Runtime Speed	Comparable; slight edge for Java in enormous/legacy apps	Nearly identical; the Kotlin K2 compiler has reduced the gap
Code Size	More verbose, larger bytecode on average	Concise syntax and smaller compiled code leads to faster loading
Null Safety Impact	More prone to NullPointerExceptions, can incur runtime overhead	Null safety reduces crashes and enhances stability
Memory Usage	Slightly lower due to minimal features	Somewhat higher if using certain Kotlin features
Concurrency Model	Traditional multithreading; high concurrency can get complex	Coroutines simplify async, improve responsiveness
Performance in Android	Reliable, stable; preferred for legacy or heavy enterprise	Native first-class Android support, efficient on modern devices
JVM Optimization	Mature, maximally optimized over decades	Continues to improve, JVM enhancements benefit both
Scalability	Stable for large-scale/enterprise solutions	More scalable designs and concurrency

Benefits and Challenges: Kotlin vs Java

Java and Kotlin both have specific advantages and disadvantages that apply to certain development needs. Below is a straightforward comparison of the main advantages and disadvantages of each language

Pros of Java

• An established language with a large, mature ecosystem and community, making it suitable for enterprise-level applications.
• Features high performance with fast startup time, benefiting from basic optimizations available from a decade of using the JVM.
• Has an abundance of usage and support for libraries, tools, and frameworks, especially useful for backend and legacy systems.
• It is generally easier for a beginner to learn due to the very verbose syntax and explicit error-handling.

Cons of Java

• Boilerplate results in a verbose syntax, resulting in code that is much longer, which lowers developer productivity and readability.
• No automatic null checking makes the code prone to NullPointerExceptions—one of the more common runtime errors.
• The threading model is more complicated than the coroutine model, which can complicate asynchronous programming and be error-prone, while also requiring developers to think differently.
• Has adopted newer language features more slowly, with asymptomatic incremental adoption of other concepts, such as Functional Programming concepts.

Pros of Kotlin 

• Kotlin uses concise, contemporary syntax that reduces boilerplate, increasing both readability and speed to develop.
• The null safety built into Kotlin removes most NullPointerExceptions, resulting in more stable code.
• Kotlin is fully interoperable with Java, allowing you to migrate gradually and reuse existing Java libraries and tools.
• Kotlin is officially supported and endorsed by Google for Android development and is superior to other options for cross-platform app development using Kotlin Multiplatform.
• The data classes and type inference make programming easier, particularly for writing data structures.

Cons of Kotlin 

• Compilation speeds can be slightly slower for clean builds of your app compared to Java, though the compilation speeds of incremental builds are comparable.
• Kotlin's modern and more expressive features might result in slightly greater learning curves if you are new to programming or programming languages other than Java.
• Kotlin's overall community and ecosystem size is smaller compared to Java's, and relatively speaking, it is rapidly growing.
• While most developers welcome the absence of checked exceptions in Kotlin, it can occasionally lead to more implicit, less explicit error handling.

Kotlin vs Java: When to Choose Each Language 

Here is the showcase of specific project consideration and use case example that will help you choose from Kotlin vs Java. 

Use Kotlin When: 

• You are developing a new Android application and wish to use features found in a modern programming language with powerful imperative capabilities and concise syntax. 
• You will be modernizing an existing Java app and wish to use Kotlin's ease and safety without a full code port.
• Your primary concern is developer experience and productivity, including code safety.

Use Java When:

• You are working with a large, traditional enterprise system that is founded on the Java ecosystem.
• The project requires Java's scope and experience; the development team knows, is comfortable, and has established processes for dependency on the ecosystem and standard practices, and supporting libraries.
• You are engaged in server-side applications and/or services where there is no question about product scale, absolute performance, and extreme stability.

Conclusion

Kotlin is an obvious winner for new Android projects because it has a shorter syntax, null safety, and is designed for modern Android development tools. Java remains a viable option for legacy projects or teams with extensive Java experience. As both languages are interoperable, you could even use both languages together as you migrate your code from Java to Kotlin.

Ultimately, the choice is based on project needs, team skill sets, and long-term outlooks. For most developers, Kotlin provides a modern, effective, and future-proof programming option for Android development.

Looking to build an Android project? Hire skilled Android app developers with Lucent Innovation.Whether you choose Java or Kotlin, our Android programmers have expertise in building feature-rich and robust solutions tailored to your specific requirements.