Kotlin vs Java: The 12 Key Differences

The debate around Kotlin vs Java has been prevalent for a while. Did you know that Kotlin was introduced as an efficient alternative to Java? If Kotlin was designed to be an improved version of Java, then why have this debate? Which is better – Kotlin or Java?  

Although Kotlin was formed after Java, their rankings tell a different story. According to RedMonk, Kotlin was one of the top 20 programming languages in the second half of 2022; however, Java was in the top five. Java and Kotlin are the two most popular programming languages for Android. This comparison of Kotlin vs Java will assist you in determining which is superior.

Table of Contents 

1) What is Java?

2) What is Kotlin? 

3) Evolution of Kotlin from Java

4) Kotlin vs Java: Difference between Kotlin and Java 

5) Which is better for Android Development? 

6) Conclusion 

What is Java?

Introduced in 1995 by James Gosling at Sun Microsystems and later acquired by Oracle in 2009, Java stands as a versatile, open-source, and object-oriented programming language. Its adaptability extends across most devices, Operating Systems (OS), and servers, thanks to its multiplatform nature. 

By utilising bytecode compilation, Java seamlessly operates on various Java Virtual Machines (JVMs). Java also boasts static typing, conducting type checks during compilation. While sharing syntax resemblances with C and C++, it offers fewer low-level features, maintaining a balance between simplicity and functionality.
 

What is Kotlin?

Kotlin, introduced in 2016, is notably younger than Java. As an open-source language, it possesses the capability to compile code to bytecode and run on the Java Virtual Machine (JVM), ensuring cross-platform compatibility. Notably, Kotlin seamlessly accommodates libraries and frameworks developed in Java within its projects.

Deriving inspiration from Java, Kotlin seeks to provide an enhanced version characterised by cleaner code, simplified syntax, faster compilation, and a harmonious blend of object-oriented and functional programming principles. Its evolution reflects a commitment to addressing shortcomings in Java while embracing modern software development practices.

Evolution of Kotlin from Java 

The formulation of programming languages has been on the run since the 1830s. ‘C’ – a programming language developed in 1972 - is still used today. Java, alongside C++ and Python, are mere derivatives of ‘C’. Similarly, Kotlin can be considered a replacement for Java, as it was made to be an easier alternative.  

Java is an object-oriented, advanced programming language. James Gosling created it in the early 1990s. The language was designed to be easy for programmers and, thus, follows a syntax similar to that of ‘C’. It is simple to use and is among the widely used programming languages today.  

On the other hand, Kotlin is a programming language that sprung up in the past decade. It was introduced by a software development company called JetBrains, and it aimed at establishing itself as the efficient and readable substitute for Java. Its compatibility with Java code has helped boost its popularity among companies like Google, Netflix, Amazon, etc. 

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Kotlin vs Java: Difference between Kotlin and Java 

Although Java and Kotlin are similar in the way they work, they also have a couple of differences. We need to understand their differences to figure out the best programming language among the two. Here are the 12 key differences between Kotlin and Java.  

a) Object-Oriented: Java is an object-oriented programming language, while Kotlin supports functional programming. This helps Kotlin produce more brief and readable code when compared to Java.  

b) Data classes: Developers in Java need to establish the fields or variables to store data, the constructor, the getter/setter functions for the fields/variables and more. However, Kotlin developers offer a simpler way to create classes ad hold data. This is done by including the keyword "data" in the class definition.  

c) NullPointerExceptions: The NullPointerExceptions in Java allow users to assign a null value to a variable. Even if an object reference has a null value, the NullPointerExceptions are brought in play. In Kotlin, null values are not assigned to variables. This is because the code stops compiling by default if it is attempted.   

d) Extension Functions: In Java, the extension function is not available. Thus, to extend the functionality of an existing class, a new class must be created. Then it must inherit the functions from the parent class. In Kotlin, the extension function is allowed. You can extend the functionality of classes without any sort of inheritance. By prefixing the class name with the function's name, the extension function in Kotlin can be performed.   

e) Casting: The process of casting an object is different in both languages. The developer needs to check the variable type in Java according to the associated operation. Meanwhile, the smart casts feature handles the casting checks in Kotlin. Redundant casts are automatically managed using the “is-checks” keyword.  

f) Exceptions: The developers of Kotlin are not required to catch or declare any exceptions. Java coders must catch and declare exceptions as they have checked exception support. Although the process of checking exceptions is tedious and time-consuming, it does help ensure error-free codes and sturdy codes. It all comes down to what the developer prioritises. 

g) Coroutines solution: In Android, components in the same application run in the same thread and process, known as the main thread. The respective calling thread is blocked when either Network I/O or CPU-intensive operations are initiated. It remains blocked till the procedure is completed. Java came up with an efficient way to handle lengthy operations. To avoid conjunction on the main thread, it allows the creation of multiple background threads. One of the cons of this solution is that handling multiple threads can be a difficult task at times. Kotlin also allows the creation of multiple background threads. But the difference is that they have an improved solution known as coroutines. Coroutines enable developers to write code, suspend executions, and later pick up where they left off.  

h) Primitive type: Variables of a primitive type are not objects in Java, while it is automatically considered an object in Kotlin upon initiation. The primitive types in Java are pre-defined data types, with eight of them.  

i) Wildcard types: In Java, a question mark (?) in code is considered a wildcard. This is linked to being an unknown type of variable, field, or parameter. However, Kotlin does not offer wildcards. A declaration-site variance and type projections act as an alternative.  

j) Public Fields: Java has public fields, and Kotlin does not. Let’s try to understand what public fields or non-private fields are first. If the callers of an object want to modify it based on the representation of the same object, public fields are a convenient option. The fields remain public, and the program can be maintained well.  

k) Implicit conversions: Java allows implicit conversions. This means that developers are not required to operate on explicit conversions. However, Kotlin does not support implicit widening conversions. Implicit widening conversion is the process in which smaller data types are converted to bigger ones. Thus, as an alternative, Kotlin developers must execute an explicit conversion to achieve the desired type.  

l) Language scripting: Kotlin can be used directly in Gradle build scripts because of its language scripting abilities. This is not possible with Java as it does not offer language scripting abilities. 

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Which is Better for Android Development? 

From a broad point of view, the odds seem to favour Kotlin. This is accurate to an extent because Kotlin carries multiple features that give it an upper hand over Java. For instance, features like built-in null safety help the language swerve away from NullPointerException errors and help in concise and readable code.  

Although Kotlin has a string of reasons to be considered the better language, Java receives massive support from the Android community. Java also has the advantage of being around longer than Kotlin. Since Kotlin is relatively new, it is still undergoing improvements.   

Considering the points mentioned above, it is safe to conclude that both are valuable for Android Development but serve different purposes at different times. Type Casting in Java plays a crucial role in ensuring seamless compatibility when working with existing projects. If you're starting a new project, Kotlin is the ideal choice, especially for an Android Developer. However, if you're handling an existing project written in Java, then Java remains the better option.

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Conclusion

Although Java and Kotlin differ in various aspects, they are highly useful programming languages. The Kotlin vs Java debate lives on because both carry valuable features important for multiple uses. We hope this blog has helped you understand the critical differences between them.