Kotlin VS Java – What's the Difference?

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Both Kotlin and Java are object-oriented languages that have been used for android application development. While Java is an old language that has been in use for years in the industry, Kotlin has gained popularity recently because of its usability in android app development. Now with the presence of both languages, a question that raises is kotlin vs java, which is the best? Both Kotlin and Java are suitable for android development, while kotlin has features like checking NullpointerException and many more, Java provides better compilation speed.

What is Kotlin?

Kotlin, developed by JetBrains, is making waves in the programming world, especially in Android app development, where it serves as a nimble counterpart to Java. With a more approachable syntax and a pragmatic approach, Kotlin has become known for its efficiency.

This versatile, statically typed, and open-source language offers robust type inference, reducing errors and streamlining code. It beautifully integrates both Android’s functional programming features and the JVM’s object-oriented strengths, resulting in improved developer productivity and faster performance compared to Java.

While Kotlin’s standard library relies on Java, leading to occasional boilerplate code, its benefits have attracted tech giants like Pinterest, Twitter, Uber, and Netflix, who have adopted it for Android app development. Recognized by Google as the second official language for Android, Kotlin’s future in the programming landscape is undoubtedly bright.

What is Java?

Java is one of the oldest and most popular programming languages in the industry. It is a general-purpose object-oriented language. Java is a class-based programming language that aids it to have fewer implementation dependencies. Java is a relatively faster and more secure language which makes it reliable. It is because Java programs run inside a virtual machine which is known as a sandbox. Java does not support explicit pointers. The byte-code verifier checks the code fragments for illegal code that can violate access rights to objects. It serves as a computing platform for application development. Java is commonly used to develop data centers, Java-based software in the system, mobile phone applications, etc.

Key Difference Between Kotlin and Java

The main difference between Kotlin and Java lies in their approach to modern programming. Kotlin, characterized by its concise syntax and robust features like extension functions and null safety, provides developers with a more streamlined and expressive coding experience. It also offers built-in support for coroutines, simplifying asynchronous programming. In contrast, Java, while powerful and widely adopted, tends to be more verbose and less forgiving when it comes to null references and checked exceptions. Java lacks native coroutine support, making asynchronous tasks more complex. Additionally, Kotlin’s introduction of data classes reduces boilerplate code, addressing one of Java’s limitations. Overall, Kotlin represents a more contemporary and developer-friendly language that builds upon Java’s strengths while mitigating its shortcomings, making it an appealing choice for modern software development.

Kotlin Vs Java: Full Comparison

In this section, we will learn about the differences between kotlin and java:

Extension FunctionsIn the Kotlin language, the feature of extension functions is readily available. It gives the programmer the ability to add more functionality to the existing classes, without inheriting them.In the Java language, we need to create a class in order to implement the extension functions.
Operator OverloadingIn Kotlin users are allowed to invoke the functions in their own provided way.In Java, the operators are tied to certain types.
Null SafetyThe feature of null safety is present in Kotlin.The Java does not provide the feature of null safety.
ConstructorsThere are two different types of constructors present in Kotlin: primary constructor and secondary constructor.In Java, there is only one constructor which is used for the initialization of the attributes with the parameters that it takes.
Static MembersThe Kotlin does not provide static members for a class.The Java provides static members for a class.
Type SystemKotlin provides the feature of type inference, nullability support, universal guard, etc.Java’s type system involves classes, primitive types, and all other kinds of a reference types that are related to the basic concept of a class, but which differ in some way, and are usually treated in a special way by javac or the JVM.
String TemplatesKotlin provides two types of string literals: escaped string and raw string.Java too has the feature of string templates but it does not have support expression like that in Kotlin.
No Checked ExceptionsIn Kotlin, exceptions are not explicitly declared in function signatures, and they occur in the program when buggy code is executed. Such exceptions are removed completely.Exception handling in Java is not as robust. For example, accessing a member of a null reference in Java results in a null reference exception.
SmartcastsThe smartcast feature is available in Kotlin, i.e. Kotlin compiler can track the conditions within an if expression. In case the compiler finds out a variable that is not null or type nullable then the compiler will allow to access the variable.The smartcast feature is not available in Kotlin.
CoroutinesKotlin offers built-in support for coroutines, making asynchronous programming more manageable and efficient.Java lacks built-in support for coroutines, making asynchronous programming more challenging.
Data ClassesKotlin provides data classes for streamlined creation of classes that primarily hold data, reducing boilerplate code.Java lacks a specific construct like data classes, resulting in more verbose code for similar purposes.

Features of Kotlin

The following are the main features of the Kotlin language:

  • Concise code: The kotlin language provides concise code, i.e. the amount of boilerplate code written in kotlin is comparatively 40% lesser than that of Java.
  • Null safety: The Kotlin language has the feature to handle nulls in a systematic way. In the Kotlin language, one does not get the null pointer exception implicitly. This is because the Kotlin compiler does not allow any type to have a value of null at compile time by default. This reduces the chances of an app crashing due to a null pointer exception. The Kotlin compiler throws NullPointerException immediately if it found any null argument is passed without executing any other statements. Kotlin's type system is aimed to eliminate NullPointerException from the code.
  • Expressive code: The code written in the Kotlin language is expressive, i.e. the code written is easily understandable. This makes it easier or anyone to understand the code.
  • Modern features: Kotlin language has introduced features like Lambda functions, transpilation, smart casts, null safety, operator overloading, etc.
  • Interoperability with Java: The Kotlin language is completely interoperable with Java, i.e. The Kotlin code can be easily called from Java and the Java code can easily call from Kotlin. This makes adoption much easier and lower risk.

Features of Java

The following are some main features of the Java language:

  • The Java language is easier to use. Java has the power of using third-party code to make writing code easier. Java is fairly simple to handle and removing bugs from it becomes easier when compared to Kotlin. The standards of safety in Java are of higher quality than in Kotlin.
  • Java is platform-independent. The Java code written on a platform can be run on any other platform.
  • Java can be used to develop object-oriented software.
  • Java is a multi-threaded language, i.e. Java provides the feature of automatic memory management.
  • Java is network-centric thus it provides the facility for distributed computing.

History of Kotlin

Following are some dates that mark important events in the history of the Kotlin language:

  • In 2016: The first version of Kotlin was launched. It was named Kotlin v1.0.
  • In 2017: Google announced first-class support for the Kotlin language in android development.
  • In 2018: Features line asynchronous programming was added to the Kotlin language. The new version was released. This was known as Kotlin v1.3.
  • In 2019: The announcement of Kotlin being the preferred language for android development was made by Google. This provided Kotlin with an ample amount of industry recognition.

History of Java

Following are some dates that mark important events in the history of the Java language:

  • In 1989: The OAK language was created by James Gosling. It is considered the initial version of the Java language. Its main purpose was to handle portable devices and set-top boxes.
  • In 1995: After the failure of OAK, the sun microsystem changed the name of the OAK to JAVA. The language was modified such that it can take advantage of the ongoing World Wide Web (WWW) development.
  • In 2009: The Sun Microsystems got acquired by the Oracle Corporation. The oracle took ownership of the following key assets of the Sun microsystem: Java, MySQL, and Solaris.

Advantages & Disadvantages of Kotlin

Advantages of Kotlin

Following are the advantages of Kotlin:

  • The Kotlin language has the feature of null safety built-in within itself. It checks the condition of NullpointerException and saves the android apps from getting crashed due to the same.
  • The Kotlin code is easy to understand thus making it easier for a new developer.
  • The large apps in Kotlin are divided into small layers thus making it easier to work and debug.
  • Kotlin offers the multiplatform framework with which one can get a common codebase that can be used to target all code segments.
  • Kotlin has provided modern features like lambda expressions, specialized language structures, etc.
  • Kotlin allows users to produce extension functions. In order to add an extension function to a class one needs to define a new function appended to the class name. The extension function allows the programmer to add more functionality to the existing classes, without inheriting them.
  • In Kotlin we can create data classes in a simple and automated manner. This is generally done using automation tools.
  • Since Kotlin is statically typed, thus it is relatively easier to write and read.
  • The information in the Kotlin can be interchangeably exchanged with Java code and vice-versa.
  • Due to simple and concise syntax, the code can be written quickly in Kotlin.
  • The deployment and maintenance are relatively easier in Kotlin due to concise code and less size.

Disadvantages of Kotlin

Following are some disadvantages of Kotlin:

  • Being a relatively new language, Kotlin has a small community thus making it difficult for people to learn or access materials.
  • The compilation speed to Kotlin is slow as compared to Java. It has been discovered Java has ~13% faster compilation speeds (with Gradle) than Kotlin.
  • Since the Kotlin language is declarative, thus is sometimes produces boilerplates that are large in amount as correspondence to JVM bytecode.

Advantages & Disadvantages of Java

Advantages of Java

Following are the advantages of Java:

  • Java has well-documented documentation available.
  • Java has a large stack of third-party libraries available.
  • Java has features to create a standard program and reusable code.
  • In Java, we can perform multiple tasks simultaneously due to its multi-threaded environment.
  • In Java, we can smoothly navigate between libraries.
  • Java has large community support.

Disadvantages of Java

Following are some disadvantages of Java:

  • Java has very less scope for automation thus developers are required to implement features manually which eventually increases the scope for error.
  • Java is not preferred for designing Android APIs due to many limitations in Java.
  • Java does not offer methods like free() or delete() thus it does not help in garbage collection.
  • Java requires a lot of memory and processing. This is because Java is a very high-level Object-Oriented programming language (OOP) that implies that while the application code itself is much easier to maintain, the objects that are instantiated will use much more memorable.
  • The programs processed through the JIT compiler are comparatively slower.
  • Low-level programming is not supported in Java thus there is no scope for pointers etc.

Which is Better (Kotlin or Java)?

Now that we have learned about both Java and Kotlin, the obvious question is Which among the two should I use?. In this section we will address the kotlin vs java discussion.

Although, there is no specific answer to this kotlin vs java debate. The Kotlin tackles multiple problems of Java-like dealing with NullPointerExceptions etc.

But when we consider factors like speed etc, Java is relatively faster in terms of compilation. Also, the large community support and longevity of Java make it a safe choice.

Overall Kotlin has been a preferred language when it comes to android development because of its feature to eliminate the need for boilerplate code, NullPointerException check, etc.

Applications of Kotlin & Java


Kotlin is primarily used to develop the following:

  • Cross-platform mobile app development
  • Native app development
  • Desktop app development
  • Server-side development
  • Data science app development
  • Web development

Trello, Pinterest, Evernote, Twitter, shadowsocks are some famous applications built upon Kotlin.


Java is primarily used to develop the following:

  • Desktop GUI Applications
  • Gaming Applications
  • Enterprise Application
  • Business Applications
  • Mobile Applications
  • Web-based Applications
  • Big Data technologies
  • Scientific Applications


  • The Kotlin vs Java debate hinges on project requirements, developer preferences, and application domains.
  • Kotlin excels in contemporary Android app development and modern software projects, while Java’s long-standing stability and community support make it a solid choice for a wide range of applications.
  • Kotlin is generally preferred for android development in Kotlin vs java situations.
  • Kotlin’s concise syntax, support for null safety, and modern features such as lambda expressions, extension functions, and coroutines make it a compelling choice for developers seeking enhanced productivity and code quality.

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