Kotlin vs. Java: What to Use for Android App Development

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Celso Crivelaro
Celso Crivelaro
Head of Engineering

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If you're trying to develop an Android app, then the chances are, you are also trying decide between whether to use the programming language Kotlin or Java. Here's the pros and cons of both.
Published on
July 13, 2023
Updated on
April 11, 2024

Kotlin and Java are two of the most popular programming languages for Android development. However, there’s a lot of debate in the programming world around which language is best. Many developers and team leaders struggle to decide between the two in their quest to launch a mobile app. In addition to Android app development, these languages can be used to build interactive websites and user interfaces, and many big-name companies use them in day-to-day operations.

When deciding whether Kotlin or Java is best, it’s essential to understand how they both work, their basic functions, pros and cons, key differences, and the best practices for mobile application development.  

What Is Kotlin?

Kotlin is often called the “Java alternative” because it can operate within the Java virtual machine (JVM), Java class libraries, and the Android environment. It is a general-purpose, statically-typed, open-source, and object-oriented language. Because it’s open-source, it’s free for the general public. Developers are free to modify and build upon Kotlin as they deem fit.

Kotlin was introduced to improve the Java language and work alongside it. Its initial release was in 2010 by JetBrains, but it wasn’t open-source until 2012. Kotlin has more than 500 contributors on GitHub.

Kotlin has also become one of the fastest-growing and widely used programming languages. Besides Android applications, Kotlin can be used to create server-side applications and in multiplatform mobile development. It has become the go-to language for many seasoned and new developers.

Kotlin Functions

Kotlin comes packed with many cool features, including:

  • Multiplatform use: Kotlin doesn’t rely on the virtual machine and can be used across multiple platforms. This helps save time on writing and maintaining code across various platforms. It can be used across Android and iOS, on server-side applications, and the front end of web development. Plus, it can be used in conjunction with Java and Java assets.
  • Lazy-loading: Kotlin supports lazy-loading, which means startup time is decreased. Android developers can use lazy loading to support loading only the necessary resources into the main memory. Users who access Kotlin-supported applications with lazy-loading enabled can see content faster than other applications.
  • Data classes: There’s much debate in the programming world surrounding the usefulness of data classes and class definitions. Many programmers argue about their necessity. In languages such as Java, data classes often comprise boilerplate code. Boilerplate code is often repetitive, but in Kotlin, data classes are simplified and written with less code, meaning that data classes are more useful when used in Kotlin than in other languages.
  • Collection filtering: Kotlin has a built-in collection filtering feature, which helps developers avoid dealing with collections independently. This feature allows developers to easily determine what each resulting list should contain.

Kotlin also has extension functions, smart casts, delegated properties, and sealed classes.

Kotlin Pros

The advantages of Kotlin are why it is favored among some Android developers and remains a popular choice in development. Some of Kotlin’s benefits include the following:

  • Clean and compact: Kotlin was designed to improve Java’s overcomplicated coding style. As such, Kotlin's clean and compact syntax contributes to a more efficient and concise coding structure. Kotlin enables developers to write less code to complete tasks. Other benefits of a clean, compact, and robust code include easy maintenance, readability, and modification.
  • Cost efficient: Kotlin is an open-source language. So, there’s no need to spend on licensing. Furthermore, Kotlin has a low cost of adoption and is easy for developers to learn. So, there are not many costs associated with learning the language.
  • Safety and reliability: Kotlin is more reliable because it requires less code. Less code means there are fewer chances of errors and bugs occurring. Additionally, Kotlin is a generally safe language with a null-safe function that helps developers avoid errors such as NullPointException.
  • Standard library use: A favorite among developers, Kotlin offers standard library functions, meaning that developers can access several library functions, including implementing higher-order functions through idiomatic patterns.

Kotlin Cons

Kotlin also has some disadvantages, which may deter some developers from using it. These disadvantages include the following:

  • Newer language: Kotlin is a relatively new language compared to Java. That is, the community isn’t as developed, and there are more chances of bugs and errors occurring with released updates. Furthermore, since Kotlin is newer than Java, Kotlin has a smaller community, so finding assistance with problems may be difficult.
  • Slower: Kotlin excels in many areas, including in build performance. However, despite that, Kotlin is still slower than Java in many areas, including when it comes to raw power. Since Kotlin was built on top of Java and requires Java to run, Kotlin’s performance can often be hindered when developing applications.
  • Difficulty hiring: Since Kotlin is new and has a smaller community, finding Kotlin developers can be challenging. This becomes even more of a challenge if you’re looking for seasoned or experienced Kotlin developers, as these developers may already be tied up in other companies.

What Is Java?

Java is sometimes confused with JavaScript, but the two programming languages are vastly different. Java was first released in 1995 by Sun Microsystems. Since then, Java has continually evolved to keep up with the modernization of the tech and software worlds. It has become the language of choice for many developers and continues to increase in popularity. But Java isn’t just a programming language. It’s also a software platform.

The Java language is both a compiled and interpreted language. That is, it is a two-stage programming language. It is also an object-oriented language that operates on several devices, including computers, mobile devices, and gaming consoles. It even operates on medical devices. Java’s syntax is based on the official language of C and C++ languages. It’s a portable language that can be moved around and used on multiple devices.

The software version of Java comprises the Java virtual machine, Java API, and the complete development environment.

Java Functions

Java has many uses, such as in mobile application development, artificial intelligence, big data, software development, web development, and more.

Java has many functions, including the following:

  • Distributed: Java was created to be distributed, meaning it can connect to several devices and share resources and information between them.
  • Dynamic: Java was also designed to be easily adaptable. Being adaptable means that it can improve performance speed while decreasing memory waste. Being dynamic also means there is strength within the Java programing language, and it’s easy to check for errors and tampering.
  • Multithreaded: Java is a multithreaded language with its own objects, allowing multiple threads to be used in a more manageable and simpler format. This enables developers to work in an easier environment with better performance.
  • Two-stage execution: Java is a two-stage programming language that goes through two different executions: compiled and interpreted. The code is first compiled and then interpreted into a particular usable format, determined by its target operating system (OS).

Additionally, Java has other features, including a ternary operator, primitive types, and implicit conversions.

Java Pros

There are many reasons why Java is popular, and its advantages contribute to its overall popularity. Its top advantages include:

  • Cost efficiency: Java can operate on various machines and devices. So, the cost of developing Java software is relatively cheap. Java also features a simple and straightforward build, helping to ease costs when developing and maintaining software.
  • Platform independence: Java functions on a write-once, run-anywhere format. This means that Java can be written on one platform and then operate on any other platform or device that is Java-friendly. Its compatibility means it doesn’t rely on operating systems or specific hardware to operate. That is, it is platform-independent.
  • Security: Java has many features that put security at the forefront and reduce the risk of unauthorized access. These features include encapsulation, abstraction, and inheritance.
  • Simplicity: Java is a simple programming language, meaning that it’s easy to use, learn, and understand. It’s straightforward and removes complicated C and C++ features like pointers, unions, and structures. In removing these features, developers can more easily implement code. 

Java Cons

Java has its fair share of complaints and disadvantages, including the following:

  • Complicated code structure: Unlike Kotlin, Java comes packed with complex verbose and syntaxes, making it complicated for newer developers to keep up with. Even seasoned developers may find it difficult to remember complicated code formats.
  • Paid commercial license: Java was once a free-to-use software. However, unlike past versions such as Java 8, Java has moved to a paid commercial licensing format. That is, users must pay to use Java, which many developers frown upon, especially since there are still many open-source and free languages available.
  • Poor performance: Java consumes a lot of memory, contributing to overall poor performance. However, that’s not the only factor contributing to its poor performance. It’s slower than other languages, has a poor GUI, and requires a significant memory space.

Differences Between Kotlin and Java

Kotlin and Java have a few similarities, such as being interoperable. However, they have many differences that stand out. It’s important to understand these differences to determine which language is right for you,

Functional vs. Object-Oriented Programming

The most significant difference is how they operate with functional and object-oriented programming. Both languages are object-oriented; however, Kotlin combines object-oriented programming with functional programming, whereas Java sticks with the former.

Shorter vs. Longer Code

Another significant difference between Kotlin and Java is their code format. Kotlin uses a simpler and more concise coding format with easier-to-understand syntaxes, while Java uses more complicated syntaxes that may be harder to learn and remember.

Use of Boilerplate Code

Boilerplate code is repetitive code used throughout software development. Java relies heavily on boilerplate code, which can make finding and debugging errors difficult, and can decrease readability and conciseness. In fact, it’s often needed to help improve quality and increase code speed. However, Kotlin doesn’t require as much boilerplate as Java, meaning it focuses more on simplicity.

How to Choose Between Kotlin and Java

Are you still struggling to decide between Kotlin and Java? There are a few other factors to consider when making your decision. 

Future-Proof Your Android App

You want your Android app to succeed. One of the most critical aspects of ensuring longevity is future-proofing your application. This means determining which language will better suit your application in the long run. Java has been around for decades and continues to evolve and grow in popularity, whereas Kotlin is relatively new, with a smaller community. Think about where these languages will be in another decade.

Reduce Costs

Cost is often an important factor when it comes to anything tech related. You won’t want to incur too much technical debt, or your product and business may fail. It’s essential to compare the prices. Both Kotlin and Java are relatively easy to learn, build on, and manage, but cost differences exist. For example, Java has moved to a paid-licensing business structure, meaning developers will have to pay a fee to access all of Java’s features. Kotlin, on the other hand, remains free to the general public.

Make Code Easier to Read

Both Kotlin and Java can improve code readability but in different ways. Many developers prefer Kotlin over Java due to its simplicity over its parent language. After all, Kotlin was created to improve Java’s code structure. So, Kotlin is often considered easier to read than Java.

Which is easier will depend on the developer. Regardless, it’s crucial to consider readability because having code that’s easier to read will ensure that you can modify code easily and find and fix bugs more efficiently.

Revelo Can Help You Choose the Best Software for Android Development

If you’re still undecided about Kotlin vs. Java for Android development, Revelo can help with decision-making. Not only can Revelo help you decide, but Revelo can also help you in finding and hiring your next developer.

Find out more about how Revelo works today and get help choosing the right software.

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