Why Java Server‑Side Teams Hesitate to Adopt Kotlin (and How to Overcome It)

After fifteen years of using Java, I wrote my first line of Kotlin five years ago; our team replaced Spring with Utterlyidle, used Totallylazy for functional programming, and became avid IntelliJ users, leveraging its Java tools.

We also experimented with Scala, but its integration complexity and slow builds limited its appeal.

When Google announced Kotlin as the official Android language in 2017, another team evaluated it for server‑side work, and most of us gave it a try.

Kotlin impressed me with its efficiency and safety, offering a more concise experience while maintaining excellent interoperability with Java, allowing incremental adoption without disrupting existing workflows.

Our interest led us to create http4k, a Kotlin HTTP toolkit, and to host Kotlin workshops for other teams.

We observed growing server‑side Kotlin usage, yet also encountered resistance for various reasons.

We Don't Have Time to Learn a New Language

Teams often claim they are too busy to learn, masking deeper issues like technical debt and low productivity. A capable Java developer can grasp Kotlin basics in a few hours and improve efficiency within days, making the investment worthwhile.

Every Java Release Gets Better

While Java evolves rapidly, it still lags behind Kotlin for simple tasks such as null‑handling. Kotlin provides many features that can be adopted incrementally, even as Java continues to improve.

As Java Developers, We're Proud

Identifying oneself with a language can create resistance to change. However, using Kotlin does not make developers obsolete; it simply reflects a willingness to adopt better tools.

Kotlin Is a Hype Language with an Uncertain Future

Initial skepticism arose when Kotlin was announced for Android, but major frameworks like Spring and Micronaut now support it, reducing the perceived risk.

I'm Using Eclipse and Don't Want to Switch to IntelliJ

Kotlin support in Eclipse is limited compared to JetBrains IDEs, which are commercial products. For the best Kotlin experience, IntelliJ remains the preferred environment.

Kotlin Developers Are Too Expensive and Hard to Hire

Salary data shows Kotlin developers earn slightly more, but senior Java developers often adopt Kotlin first, dispelling the notion that Kotlin talent is scarce or overly costly.

Kotlin Is Too Complex

Kotlin balances ease of use with advanced features, offering good Java interop. Beginners should stick to core Kotlin features before exploring more sophisticated constructs to keep codebases maintainable.

Using Two Languages in One Codebase Is Confusing

Mixing Java and Kotlin is manageable; a useful rule is to convert existing Java code to Kotlin when a change involves both languages, enabling gradual migration without massive rewrites.

We Prefer Java

Some teams see no need for Kotlin when Java suffices, but this is usually an exception driven by time or interest constraints rather than technical limitations.

I Don't See the Benefits of Kotlin

Kotlin’s conciseness and safety are its main advantages, yet many developers overlook them because they are accustomed to Java’s verbosity.

Some Thoughts

Adopting a new language is challenging for most teams, but I encourage Java server‑side developers to give Kotlin a try when the opportunity arises.