Table of Contents

Kotlin vs Java Comparison

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When it comes to Android app development, Java will probably be the first programming language to spring to your mind. However, Kotlin is expected by many to kill Java, is it true? Let’s find out!


So, Kotlin is an open-source, general-purpose programming language.


  • Conciseness: It allows us to solve the same problem by writing less code.
  • Interoperability: It’s a hundred percent compatible with the ecosystem of Java frameworks, tools and libraries.
  • Vibrant community: It has a strong and supportive community of programmers.
  • Safety: It eliminates a significant number of coding errors.


  • Slow compilation: Java is 17% faster than Kotlin for compiling clean builds.
  • Lack of experienced developers: because Kotlin is only gaining popularity.
  • Steep learning curve. So, it will take your team some time to learn Kotlin up front.

One of the most popular apps that are built using Kotlin is Trello. Does your team use it for workflow organization?


For Android development, we use Java 7 as default, while Java 8 version has been supported natively since Android SDK 26.
Java is an object-oriented, multi-platform programming language.


  • Easy to learn: It has an understandable syntax.
  • Platform-independent: The compiler allows converting Java source code to bitcode, which is an intermediate language.
  • Large community. So, there are a lot of resources available online.
  • Abundant API that can be used to build integrations between different applications and make them communicate with each other.
  • Secure: Java has a range of built-in security features.


  • Verbosity: as Java requires more lines of code.
  • Performance: as it’s considerably slower than other languages.
  • Costs: as Java applications need more resources and have high processing requirements.

Differences between Kotlin and Java

Null Safety

  • Java allows users to attribute a null value to any variable, leading to development errors.
  • In contrast, the Kotlin language has built-in null safety.

Data Classes

  • As a rule, Java developers are required to define constructors, getter & setter methods and variables to store the data. Java record is not supported in the Java version used for Android development.
  • Kotlin on the contrary, makes the creation of classes a lot easier.

Extension Functions

Another Kotlin advantage over Java is the ability to extend the functionality of classes.

Smart Casts

  • In Java, the engineers are required to check the type of variable per the operation to cast an object.
  • Kotlin on the contrary, provides a smartcast feature that handles the casting checks.

Type Inference

  • Java makes it mandatory to specify the type of each variable explicitly.
  • In Kotlin, it’s quite the opposite.


Similar to Java, Kotlin also offers developers the ability to create multiple threats. However, it can also boast a more efficient way to solve this issue, that is Coroutines.

Checked Exceptions

  • Java provides support for checked exceptions.
  • Kotlin on the other hand, doesn’t have checked exceptions.

Primitive Types

There are eight different data types in Java. However, when developers initiate a variable of primitive type in Kotlin, it is considered an object.

Wildcard Types

Unlike Java, Kotlin has no wildcards.

Implicit Widening Conversions

  • Kotlin doesn’t provide support for implicit widening conversions.
  • Contrary to this, Java supports implicit conversions.

Code Conciseness

So, Kotlin requires fewer lines of code than Java to perform the same operations necessary. Google’s claim that Kotlin is the preferred language for Android development serves as an absolute proof that the language has undeniably a bright future and perspectives ahead.

So, will Kotlin fully replace Java for Android development or not?

This article was prepared by the EZtek team. We help top brands worldwide to innovate and accelerate digital transformation. We share the latest news about tech trends and innovations. So make sure to subscribe not to miss a single blog.


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