java -version

Many older corporate tools were built specifically for the Java 6 runtime and will not launch with newer versions like Java 8 or 17.

Developers often need to maintain or "debug" legacy codebases that rely on libraries no longer supported in modern Java.

If you are a modern developer, you are likely used to Java 17 or 21. But if you are reading this, you probably have a very specific reason: you are maintaining a legacy enterprise system, trying to get an old game to run, or working with an antique application server that refuses to die.