Development Solutions2023.08.09By: Miichisoft

Key Differences Between Java and Kotlin: Will Kotlin Be the Solution of the Future?

JavaとKotlinの主な違い。Kotlinは未来のソリューションとなるでしょうか?

Kotlin is a programming language that Google has adopted as an official language for Android app development. Java is another powerful programming language that can also be used for Android app development, and many people struggle to decide which one to use. This article explains the differences between Kotlin and Java, along with the pros and cons of each.

1. Overview of Java and Kotlin

1.1. Overview of Kotlin

Kotlin is an open-source language backed by JetBrains and Google through the Kotlin Foundation. Because it runs on the Java Virtual Machine (JVM), it works on almost any platform. It's also designed to be fully compatible with Java, so Kotlin projects can use Java libraries and frameworks. What's more, switching from Java to Kotlin can be done seamlessly just by installing a single plugin.

Inspired by Java, Kotlin aims to be a cleaner, simpler, and faster improvement. It offers a combination of object-oriented programming (OOP) and functional programming.

1.2. Overview of Java

Java is a multi-platform, network-centric, object-oriented programming language. Developed by James Gosling in 1991 and released by Sun Microsystems in 1995, it remains one of the most widely used programming languages today. With Java, you can build a wide range of applications, including desktop apps, enterprise apps, and cloud- and web-based apps. It's typically used for backend development. For Android app development, Java is a primary choice for developers — Android itself is written in Java.

1.3. Why Compare Java and Kotlin?

Java is one of the most popular and widely used programming languages, while Kotlin is a relatively new competitor. The latter hasn't yet replaced the former, but it has proven to be an excellent alternative for Android app development.

One year after its launch, in 2017, Google recognized Kotlin as the second official language for Android development, a major highlight at I/O 2017. Until then, Java had been the only official language for development on the Android platform. Since then, Kotlin's popularity has steadily grown as a highly favored Android development language. In 2019, Kotlin was declared Google's "recommended programming language for Android app development." Given its rapid growth and status as Google's recommended language, many Android developers may wonder whether Java or Kotlin is better or more suitable.

2. Key Differences Between Java and Kotlin

Now that you understand the background, you might wonder how Kotlin's growth will affect Java. Well-suited for creating callbacks, data classes, and getters/setters, Kotlin produces lightweight, concise code, which is why major companies like Twitter, Pinterest, Netflix, and Uber have adopted it. Switching to Kotlin has recently become popular in Android app development as well, and opinions are mixed on whether Kotlin could eventually replace Java. To understand both sides of the debate, let's first look at the table below.

2.1. Java vs. Kotlin Comparison Table

	Kotlin	Java
Programming Concept	Kotlin combines features of both object-oriented and functional programming. It supports modern programming concepts such as delegation, extension functions, and higher-order functions	Java is limited to object-oriented programming
Developer	JetBrains	Oracle
Purpose	Used for server-side app development, Android app development, and more.	Used for standalone app and enterprise app development, among others
Platform Compatibility	Kotlin supports compiling not only to bytecode and JavaScript, but also to native code	Java only compiles to bytecode for the JVM and JavaScript
Compilation Speed	Slower	Faster
Code Brevity	Reduces lines of code by half	Twice as many lines as Kotlin
Conciseness	Reduces the use of boilerplate code	Uses more boilerplate code
Extension Functions	This feature lets you extend existing classes with new functionality	Extension functions aren't supported. You have to create a new class
Type Conversion	Doesn't provide implicit type conversion, so smaller types can't be converted to larger ones	Doesn't provide implicit type conversion
Coroutines	Using Coroutines, a concurrency design pattern that simplifies code, lets you suspend a specific thread when creating multiple threads without blocking the others	Java's multithreading features (RxJava and Project Loom) can block threads during operations such as network I/O or CPU work, making the code more complex
Smart Cast	Supports Smart Cast, which identifies immutable types and automatically performs implicit casting	Doesn't support Smart Cast
Data classes	A class can be declared with just the data keyword	Declaring a class requires building many elements. To create a class that only holds data, you must define getter/setter methods, constructors, and other functionality
Data Type Specification	Doesn't require specifying the data type of variables	Requires explicitly specifying the data type
Null Values	Null values can't be assigned to variables or objects	Null values can be assigned to variables, but not to objects
Null safety	Null safety is built into Kotlin's type system	NullPointerException occurs because Java has no null safety feature
Checked Exceptions	Eliminates checked exceptions entirely. There's no need to catch or declare them	Implementing checked exceptions in Java is a problematic process
Public Fields	None	Provides a convenient public fields feature that lets you change an object's representation without adjusting the caller
Wildcard-types	None	Available
Lambda Expression	Available	Only added in Java 8
Lazy-Loading	Available	None
Operator Overloading	Operators can be customized	Tied to specific Java types
Community Support	Not as large as Java's	A very large community

Table 1. Java vs. Kotlin Comparison Table

2.2. Why Choose Java

Advantages of Java	Disadvantages of Java
Easy to learn Safer thanks to powerful development tools Platform independence: create reusable code that runs on any computing platform Automatic memory management Massive community support Detailed documentation available Support from experienced developers Third-party libraries available Easy to work with libraries	Java's syntax and code are complex and verbose Not well suited to Android API design Increases the number of potential errors and requires more work Relatively slow with the JIT compiler and has high memory and processing requirements Doesn't provide functions like delete or free, so garbage collection can't be controlled Doesn't support low-level programming constructs such as pointers

Table 2. Why Choose Java

2.3. Why Choose Kotlin

Advantages of Kotlin

Disadvantages of Kotlin

Kotlin uses the JVM to combine OOP and functional programming features

Compatible with existing Java code and interoperable with Java

Fewer bugs

High reliability

Provides a rich API for app development with built-in null safety support

More concise and expressive than Java

Can use special language constructs like lambda expressions

Support for extension functions

Automated data class creation process

Lets you split large apps into smaller layers

User-friendly and easy to understand

Has code-trimming capabilities

Shorter time to write new code, reduces cost, time, and effort while improving speed and performance, and is easy to deploy and maintain even at scale

Being a newer language, its developer community is still small

High memory consumption, no checked exceptions, and slower compilation speed

Table 3. Why Choose Kotlin

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3. Analysis of Kotlin's Future Potential

As if trusting Kotlin's promise of accessibility across all platforms and app scalability, more and more enterprise leaders (Twitter, Airbnb, Netflix) are switching their Android app development to Kotlin. So let's dig deeper into Kotlin's advantages and talk about its future potential.

3.1. 5 Reasons to Choose Kotlin in the Future

3.1.1. Kotlin Is Concise and Simple

Code brevity isn't one of Java's strengths. Kotlin, on the other hand, offers something far more concise and readable.

Kotlin's concise code can reduce the time, cost, and effort needed for error scanning and fixing or enhancing changed code.

3.1.2. Interoperability Through Bytecode

Kotlin's interoperability lets you access all libraries and create modules that work seamlessly with existing Java code. Using the Kotlin compiler, you can run both languages simultaneously in the same project.

3.1.3. Null Safety and Automation

Kotlin has a built-in, automated null safety feature that removes the need to write extra workaround code. NullPointerException, on the other hand, is often the source of errors that can easily undo all the hard work put into app development.

In other words, when it comes to problem-solving and optimizing the development process, Kotlin can be said to outperform Java.

3.1.4. Shortening the Project Timeline

For businesses, the conciseness of Kotlin's coding is a valuable asset. It saves time spent on code development, code changes, code review, and bug fixes.

This reduces both the project schedule and cost, giving you a significant competitive advantage.

3.1.5. Product Quality and Support

In Java coding, the presence of an error doesn't just mean an error — it can lead to terrible outcomes like app crashes. It also means spending a huge amount of time identifying the error and examining the code. The bigger the code, the more time and effort it takes.

It also lets you make the app interface far more concise, giving you a better sense of control and clarity during the development process.

Using Kotlin makes it easier to fix bugs and crashes, and it comes with long-term support.

3.2. Analysis of Kotlin's Future Potential: Will Kotlin Be the Solution of the Future?

In Android app development, Kotlin can be said to be an excellent language, but the Kotlin vs. Java debate has two sides. Let's start by talking about the current situation.

Because Kotlin is a relatively new language, there's a lack of information available. This gap can often become an obstacle to problem-solving for developers. As a result, it can be an issue for developers who don't know how to solve, using Kotlin, certain problems that could otherwise be solved with Java.

Next, let's talk about the future. With its reduced workload and excellent features, Kotlin could become the language of choice for developers going forward. Since Kotlin's announcement, the number of lines of code used each year has nearly doubled, and the Kotlin community has grown from 2.1 million lines in 2016 to over 15 million lines today in 2023. This shows Kotlin's rising popularity.

Given this situation, it's fair to say that Kotlin replacing Java in the long run is inevitable.

4. Conclusion

Therefore, switching from Java to Kotlin requires caution. Since there are risks such as class removal that could affect your product architecture, companies should start preparing for the switch even if they don't choose to make it right away. This is because the switch could become essential for businesses to maximize their competitiveness.

Before switching, the development team needs to analyze market trends and Kotlin's growth to determine whether they're ready for the switch. This allows them to make a more informed and appropriate decision.

Miichisoft is a Vietnamese technology company with strong expertise in developing Android apps using languages such as java kotlin. We have supported numerous cross-platform development projects for Japanese clients. We've developed a total of over 150 projects, including mobile app projects with more than 1 million downloads and active use. If you're interested in Android app development or similar, please feel free to contact us.

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