Can You Use Kotlin and Java in the Same Project Android Studio?

Android, Android Studio

Can You Use Kotlin and Java in the Same Project Android Studio?

If you’re an Android developer, you may have come across the question of whether it’s possible to use both Kotlin and Java in the same project in Android Studio. The good news is, yes, you can! Android Studio provides seamless integration for both languages, allowing developers to leverage the strengths of each.

Why Use Kotlin and Java Together?

Kotlin and Java are both officially supported programming languages for Android development. While Java has been the traditional language for building Android apps, Kotlin has gained popularity due to its concise syntax, enhanced null safety, and other modern language features. By using a combination of both languages, developers can take advantage of the existing Java libraries and frameworks while enjoying the benefits of Kotlin.

Setting Up a Project with Both Languages

To use both Kotlin and Java in the same project in Android Studio, follow these steps:

  1. Create a New Project: Start by creating a new project in Android Studio as you would normally do.
  2. Add Kotlin Support: During project creation, select “Include Kotlin support” or add it later through “File” > “New” > “Kotlin Class/Activity/Fragment”.
  3. Create a New Java Class: Right-click on your project’s package directory and select “New” > “Java Class”.
  4. Add Existing Java Code: If you have existing Java code that you want to use in your project, simply copy and paste it into the newly created Java class.

Mixing Kotlin and Java Code

In an Android Studio project that supports both Kotlin and Java, you can freely mix code written in both languages. This means you can call Kotlin functions from Java classes and vice versa.

Calling Kotlin Code from Java:

  • Create a new instance of the Kotlin class using the new keyword.
  • Access methods and properties of the Kotlin class using dot notation.

Calling Java Code from Kotlin:

  • Kotlin automatically imports all Java classes, so you can directly use them without any additional steps.
  • To access static methods or fields of a Java class, use the class name followed by dot notation.

Differences Between Kotlin and Java

While both languages ultimately compile to bytecode that runs on the JVM (Java Virtual Machine), there are some key differences between them:


Kotlin has a more concise syntax compared to Java. It eliminates boilerplate code, such as semicolons, parentheses for if statements, and explicit type declarations in many cases.

Null Safety:

Kotlin has built-in null safety features that help avoid null pointer exceptions. It introduces nullable and non-nullable types, forcing developers to handle nullability explicitly.

Extension Functions:

Kotlin allows developers to add extension functions to existing classes without modifying their source code. This improves code organization and readability.

Data Classes:

Kotlin provides data classes that automatically generate common boilerplate code like equals(), hashCode(), toString(), etc., based on the defined properties. This reduces manual coding effort.

In Conclusion

Using Kotlin and Java together in the same Android Studio project is not only possible but also a great way to leverage the strengths of both languages. By combining their powers, you can write clean, concise, and robust code while making use of existing Java libraries. Whether you’re a fan of Kotlin’s modern features or prefer the familiarity of Java, Android Studio has you covered.