Why migrate from RPG to Java?
If you're considering modernising your IBM i applications, the choice of target language is one of the most important decisions you'll make. Here's why Java is, for most organisations, the right answer.
The most important factor: who will maintain the code?
The choice of migration target should be driven by one question above all others: which language will your team be able to hire for, train on, and maintain confidently in 10 years?
Java has more than 10 million active developers globally. It is taught in virtually every computer science programme in the world. It is the language behind most of the world's enterprise systems — from banking to healthcare to logistics. When you post a Java job, you get hundreds of qualified candidates.
RPG has a few thousand remaining developers, most approaching retirement. Even Python and TypeScript — popular in web development — have shallower enterprise ecosystems when it comes to the kind of mission-critical, transactional business logic that RPG applications typically contain.
"The right migration target is the one you can hire for. That's Java."
Java runs on IBM i — enabling phased migration
IBM i has supported the Java Virtual Machine (JVM) since V4R2. This means Java applications can run natively on the same hardware as your existing RPG systems — no immediate need to change your infrastructure.
The practical implication is significant: you don't have to do a "big bang" cutover where you turn off the old system and turn on the new one on the same day. Instead, you can run Java and RPG side by side during the transition — migrating module by module, testing thoroughly, and cutting over to Java for each piece when it's ready.
This phased approach dramatically reduces migration risk. At any point in the process, you still have your working RPG system. You only retire a module when its Java replacement has been fully validated.
No other major migration target (Python, C#, TypeScript) offers this same native IBM i compatibility. This is one of the most technically compelling reasons to choose Java.
Comparing migration targets
| Criterion | Java | Python | C# | TypeScript |
|---|---|---|---|---|
| Runs on IBM i natively | ✓ | ✗ | ✗ | ✗ |
| Developer talent pool | Very large | Large | Medium | Large |
| Enterprise ecosystem | Excellent | Good | Excellent | Growing |
| Long-term stability | 30+ years | Good | Good | Newer |
| IBM i migration track record | Proven | Growing | Some | Rare |
| Static typing (safer for migration) | ✓ | ✗ | ✓ | ✓ |
Note: We also offer RPG-to-Python migration. If your situation makes Python the better fit, we'll tell you honestly. Our goal is a successful migration, not pushing a single technology.
A language your organisation will still be using in 20 years
Java was released in 1995. For 30 years it has maintained backward compatibility with extraordinary discipline — code written in Java 8 in 2014 still compiles and runs without modification.
The language is governed by the Java Community Process (JCP), a formal specification process that ensures changes are deliberate and well-considered. The JVM is the most battle-tested managed runtime in existence, running everything from Android devices to the world's largest financial systems.
For organisations that are migrating away from a 30-year-old system, the long-term stability of the new platform is not optional — it's a core requirement. Java is the only widely-adopted modern language with a comparable track record of backwards compatibility and enterprise stability.
Talk to us about whether Java is the right target for your codebase.
Every codebase is different. The Migration Pilot will give you a concrete answer on your own code — including an honest view of whether Java is the right target for your situation.
Start with a Migration PilotEUR 3,000 fixed price. 15-day money-back guarantee. We respond within 2 business days.