Java to Kotlin

Available in: IntelliJ IDEA Ultimate

Use this page to configure AI-assisted Java-to-Kotlin conversion: the model that performs the conversion, its execution limits, and the skill and refinement rules that shape the generated Kotlin.

Model

Item	Description
Model	Select the model that performs the conversion. The list includes JetBrains AI models and any models from third-party providers you have configured. Which models are available depends on your subscription and provider configuration.
Configure providers	Opens the Providers & API keys page, where you can use your own API key or a local endpoint, for example, Ollama or LM Studio, for the conversion.

Execution

Item	Description
Retry attempts	The number of times AI Assistant retries a failed model call before it stops. Default: 3. Range: 1–5.
Timeout per attempt	The time limit for a single model call, in seconds. If a call does not finish within this time, AI Assistant cancels it. Default: 60. Range: 10–600.

Installed Skill

AI-assisted conversion uses the kotlin-tooling-java-to-kotlin skill to refine the generated Kotlin. Basic conversion works with built-in defaults, but the framework-specific refinements described below require this skill to be installed.

Item	Description
Status	Shows whether the skill is installed, installed but disabled, or not installed. When the skill is not installed, the page shows a message that the `kotlin-tooling-java-to-kotlin` skill is required to enable AI-assisted conversion.
Install	Opens the Skills page, where you can install the skill. This button does not install the skill directly.

Always Applied

These refinements apply to every file during conversion. Both are enabled by default. To view or customize the underlying rules, click the edit icon next to a refinement; to revert your changes, click Restore Default. Editing is available only when the skill is installed.

Item	Description
Conversion methodology	Applies the staged conversion methodology from the installed skill so the generated Kotlin follows a consistent approach.
Known issues	Anticipates common conversion pitfalls catalogued in the installed skill.

Framework-Specific (Auto-Detected per File)

AI Assistant detects the frameworks used in each file by scanning its imports and applies the matching refinements. All options are enabled by default and require the kotlin-tooling-java-to-kotlin skill. When the skill is not installed, these options are unavailable and the page shows a hint to install it. To customize a refinement, click the edit icon next to it.

Item	Description
Spring	Refines Spring beans, configuration, and annotations (`org.springframework`).
Lombok	Replaces Lombok annotations with idiomatic Kotlin equivalents.
Hibernate / JPA	Refines JPA entities and Hibernate mappings (`org.hibernate`, `jakarta.persistence`, `javax.persistence`).
Jackson	Refines Jackson serialization annotations (`com.fasterxml.jackson`).
JUnit / TestNG	Refines test classes for JUnit and TestNG.
Mockito	Adapts Mockito patterns to Kotlin, for example, open classes and mockito-kotlin idioms.
RxJava	Refines RxJava streams (`io.reactivex`, `rx`).
Dagger / Hilt	Refines Dagger and Hilt injection modules and components.
Guice	Refines Guice modules and injection annotations (`com.google.inject`).
Micronaut	Refines Micronaut beans and configuration (`io.micronaut`).
Quarkus	Refines Quarkus CDI and enterprise APIs (`io.quarkus`, `jakarta.enterprise`).
Retrofit / OkHttp	Refines Retrofit interfaces and OkHttp clients (`retrofit2`, `okhttp3`).

For the conversion workflow, refer to Convert Java to Kotlin.

11 August 2026