Can we add features without a rewrite?

Almost always. A working Java codebase takes new functionality directly, and new work can be written in Kotlin inside the same project. A rewrite is worth discussing only when the existing structure makes every change disproportionately slow and risky.

What if the app uses very old libraries?

That is the usual starting point and normally the first thing worth fixing. Old support libraries, outdated Gradle versions, and abandoned dependencies cause most of the friction. Updating those often resolves problems people had blamed on the language.

Can Java and Kotlin run in the same app?

Yes, and this is how most Android modernization actually happens in practice. The two compile together and call each other freely, so a project can shift over years instead of one release, with no period where nothing ships to users.

What kinds of apps can Java build?

On mobile, effectively anything Android supports: consumer apps, internal business tools, software for managed device fleets, and applications integrating with hardware or enterprise systems. Java also runs server side, which our Spring Boot page covers.

Java Mobile
App Development

Stateside Digitals provides Java mobile app development for businesses running Android applications built in Java, keeping them current, secure, and able to take new features without a rebuild you never budgeted for.

Java built Android. For more than a decade it was the only realistic way to write an Android application, which is why a large share of the apps running on phones today have Java somewhere inside them. Google named Kotlin its preferred language in 2019, but that announcement did not retire any of the Java already working in production.

For a business, that history is the entire point. If your Android app is more than a few years old it is probably written in Java, and it probably still works fine. The real question is not whether the language is fashionable. It is whether your app keeps meeting Play Store requirements, running on current devices, and taking new features affordably.

Already In Production

Your App Already Runs On It

Working software has value a rewrite throws away, along with years of fixes for problems nobody on the team remembers encountering.

Deep Android History

Every API Has Java Support

Android’s whole platform surface has been reachable from Java since the beginning, so nothing your app needs is out of range because of it.

Works Beside Kotlin

Both In One Project

The two languages compile together in one app, so modernizing becomes something you do gradually rather than all at once.

Existing App Maintenance

Keeping a live Java Android app compatible with new OS versions, current devices, and the Play Store rules that change every year.

Enterprise Android Rollouts

Internal applications distributed across company-owned devices, where Java codebases are common, deployment runs through device management, and downtime has a real cost.

Feature Additions

New functionality added to an app that works, written cleanly enough that it does not make the next change harder than this one.

There is no urgency here, which is worth saying plainly because plenty of agencies will tell you otherwise. Java Android apps still build, still ship, and still pass Play Store review. Google has not deprecated Java support for Android and has given no sign of intending to. A working Java app is not a problem waiting to happen.

What does shift over time is everything around it. New Android libraries and documentation arrive Kotlin-first, and hiring gets gradually harder. So the sensible answer is usually neither standing still nor rewriting. Write new code in Kotlin, leave working Java alone, and convert individual files only when you were going to open them anyway.

We work with Java on current Android SDK versions, building against AndroidX and Jetpack libraries rather than the deprecated support libraries older projects often still carry. Networking runs through Retrofit, local storage through Room, and testing through JUnit and Espresso. Builds run on Gradle, and Kotlin is introduced alongside Java wherever it genuinely earns its place.

Java
Kotlin
Android SDK
AndroidX
Jetpack
Retrofit
Room
JUnit
Espresso
Gradle
Play Store
Spring Boot

Existing Code Respected

No Forced Rewrites

Dependencies Modernized First

Migration Paths Documented

We read what is there before proposing changes, because years of fixes are usually holding up more than the structure suggests.

A rebuild gets recommended only when the existing structure makes every change disproportionately slow, not as the default opening quote.

Old support libraries, stale Gradle versions and abandoned packages get addressed before anything else, since they cause most of the friction.

Where Kotlin is introduced, the boundary and the reasoning are written down, so a part-migrated project stays legible to whoever opens it next.

Existing Code Respected

No Forced Rewrites

Dependencies Modernized First

Migration Paths Documented

Yes. Java remains fully supported by the Android SDK and toolchain, and apps written in it build and publish normally. Kotlin is the recommended language for new projects, but recommended is not the same as required, and nothing has been withdrawn.

Java Mobile
App Development