Kotlin vs. java: which programming language is better?

Kotlin and Java are both programming languages, and both have their vocal supporters, as well as their detractors. But which one is going to be better for your website or project? Let’s go over the difference between Kotlin and Java. 

What is java?

Java is an OOP, or object-oriented programming language, that came out in 1995 and over 12 million developers today. It was developed at Sun Microsystems, which was later acquired by Oracle. If you want to run a Java program on a browser, you need to use Java applets, which are embedded as a plugin. Java is mostly used for back-end development or standalone applications. 

What is kotlin?

Kotlin is a relatively new but named as one of the most popular programming languages for the end of 2019. Programmers developed it from IDE JetBrains. Kotlin is a statically-typed programming language, like Java or C++. It is based on JVM (Java Virtual Machine), but it can be compiled to JavaScript, Android, and Native for building code and running on iOS. Kotlin is compatible with existing Java stacks and features a smooth learning curve. For those who are involved in the debate of Kotlin vs. Java, Android apps that have smooth UX might be your ultimate goal. 

Java vs. kotlin: which is better?

Some programmers ask the question of which of these two is better, and whether they should be switching from Java over to Kotlin. That is going to depend entirely on your preferences. If you’re thinking about making the switch, though, it’s vital to understand the distinctions between these two programming languages. Kotlin vs. Java performance is going to be a matter of opinion to some extent, but some facts about these languages are undeniable. 

Checked exceptions

In the Java vs. Kotlin debate, here is one area worthy of your attention. Unlike Java, Kotlin has no provision for checked exceptions. There is no need to catch or declare any of them.

If a developer working in Java finds it infuriating to try and catch blocks in the code, then the omission made by Kotlin will be considered a welcome change. However, it’s the opposite if the developer believes that checked exceptions encourage error recovery and the creation of more accurate code.

which programming language is better Kotlin vs. java
Photo: Christina Morillo, Pexels.

Code conciseness

When you compare a Java class with an equivalent Kotlin one, it demonstrates the conciseness of Kotlin’s code. A Kotlin class needs less code to perform the same operation that a Java class does. When looking at Kotlin vs. Java for Android development, this is probably going to be a factor. 


CPU-intensive work and network I/O would be considered long-running operations. The calling thread is blocked until the whole process is completed. Android is single-threaded by default. This means that an app’s UI gets frozen as soon as the main thread is blocked. The traditional solution for this problem in Java is to create a background thread for intensive or long-running work. 

However, there is an arguably better way of managing intensive operations in Kotlin, known as coroutines. Coroutines are stackless. This means they demand lower memory usage as compared to threads.

Coroutines can perform long-running and intensive tasks by suspending execution without blocking the thread and then resuming the execution later. It allows the creation of a non-blocking asynchronous code that seems synchronous. The code using coroutines is both clear and concise.

Data classes

Full-size projects have different classes that are solely intended to hold data. Such classes have little or no functionality; developers need to write a lot of boilerplate code in Java.

Kotlin has a simpler way of creating such classes. The developer need only include the data keyword in the class definition. The compiler will then take care of the whole task on its own.

Extension functions

Kotlin allows developers to extend a class with new functionality through extension functions. Creating such features is easy in Kotlin. You do it by prefixing the name of the class that needs to be extended to the name of the function you are creating. 

Kotlin is functional

Kotlin could be thought of as an object-oriented language. Like with most of the modern programming languages, though, it uses some concepts of functional programming. Those might include things like lambda expressions and high order, or functions that accept other functions as parameters.

Kotlin’s functions are first-class. They can be stored in data structures and variables, which can then be passed as arguments to and returned from other higher-order functions.

As a statically-typed programming language, Kotlin uses a range of function types for representing functions. 

Implicit widening conversions

In Kotlin, there is no support for implicit widening conversions for numbers. Because of this, smaller types aren’t able to get converted to larger ones. Java has support for implicit conversions, while Kotlin is required to perform an explicit conversion to achieve an implicit one.

Native support for delegation

In programming jargon, delegation is the process where a receiving object delegates operation to a 

second delegate object. Kotlin supports composition over an inheritance design pattern through the first-class delegation, also called implicit delegation.

With Kotlin, class delegation is an alternative to inheritance. This allows you to use multiple inheritances. Also, Kotlin’s delegated properties prevent code duplication, a feature many programmers love.

Null safety

One of the most irritating issues with Java for developers is the NullPointerExceptions. Java lets developers assign a null value to any variable. However, if they try to use an object reference that has a null pointer value, the NullPointerException comes into play.

Kotlin is null safe, so this is never an issue. If you do encounter such an exception in Kotlin, then it is likely that either you explicitly assigned a null value or it is due to external Java code.

Data classes

Why use Kotlin? Well, another great feature with it is the way you can create data classes. In Android, most of the applications are data-driven. This means you can spend a lot of time creating classes with only properties and fields to hold data. In Java, it’s a tedious process. In Kotlin, you can do it in a single line.

Kotlin or java which programming language is better
Photo: Startup Stock Photos, Pexels.

Smart casts

Before an object can be cast in Java, you have to check type. Unlike Java, Kotlin comes with the smart casts feature. This automatically handles redundant casts. You don’t need to cast inside a statement provided it is already checked with the Kotlin “is operator” feature.

No static members

Kotlin has no provision for static members. To have its class level functionality, companion objects are introduced. The advantage of this is that everything is an object. In the debate of why Kotlin over Java, this is a feature that is often cited. 

Support for constructors

A Kotlin class, unlike a Java one, can have one or more secondary constructors as well as a primary one. You can do this by including these secondary constructors in the class declaration.

Ternary operator

Unlike Kotlin, Java has a ternary operator. The Java ternary operator works like a basic “if” statement. It contains a condition that evaluates to true or false.

Wildcard types

In generic code, “?” represents an unknown type. This is called the wildcard. There are several uses for it, including as the type of a parameter, field, or local variable.

Java’s type system offers wildcards, but Kotlin does not. However, it has declaration-site variance and type projections as alternatives. If you’re looking at which to learn, Kotlin vs. Java, the presence of these features would seem to put the two systems on par with one another. 

Is kotlin better than java?

Even after reading to this point, this likely won’t be an easy question to answer. Developers can probably get away with not making the switch to Kotlin. Still, they’re likely to encounter the language at some point. 

If you are already familiar with Java, learning Kotlin should not pose any problems. The language is going to impact app development on a massive scale, so it wouldn’t hurt to learn its basics. Also, growing with modern techniques and styles will aid any developer. You want to be seen by potential employers as having kept up with the times. 

Business benefits of switching to kotlin

  • Reduced Project Timelines: Kotlin’s brevity means the language can solve more problems with fewer code lines. 
  • Fewer App Crashes: Since Kotlin products use fewer lines of code compared to Java programs, fewer app crashes are likely. Less code reduces development time, and fewer lines of code generally equate to less need for maintenance.

So, which is better, Kotlin vs. Java? We would argue that both are beneficial, and you’re likely to find a use for each of them the longer you work as a programmer.

If you got your start with Java, there’s no reason your education should stop there. Adding Kotlin to your repertory will make you a more well-rounded programmer and a more valuable employee.

Slava Vaniukov
Slava Vaniukovhttps://www.softermii.com/
Slava Vaniukov, Co-Founder and CEO at Softermii, has over 9-years of experience in the web and mobile development industry as a Software Architect. After getting extensive experience as a Senior Tech Lead, Slava joined forces with like-minded professionals to start own company. Besides that, he is one of the authors at the Softermii blog and tech blogger featured at a wide range of other web resources.
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