Java requirements?

[caj411]

I have Windows 11 with JDK and JRE 21 Temurin installed, but it keeps telling me I need JRE 17 installed. I installed the Adoptium versions it directed me, but no cigar. Is there something I'm missing here? Isn't Java backwards compatible?

[joemar25]

Java is indeed backwards compatible, which means that an application built for a lower version can run on higher versions of Java. However, the reverse is not true. An application built for a higher version of Java cannot run on lower versions.

In your case, if you have an application that requires JRE 17, it means that the application was built with features from Java 17. While you have JDK and JRE 21 installed, the application cannot run on this version because it doesn't recognize the features from Java 17.

To resolve this issue, you have a few suggestions:

1. Install JRE 17 alongside your existing JDK and JRE 21. This allows you to run applications that require Java 17.
2. If you have control over the application's source code, you could try to compile your application for Java 17, ensuring it doesn't use features from later Java versions.
3. Bundle a Java runtime within your application. This way, you have complete control over the Java version used at compile-time and runtime.

Remember to set the JAVA_HOME environment variable to point to the correct JDK or JRE version when running your application.

For the JRE and JDK:
https://adoptium.net/en-GB/temurin/releases/

From Stackoverflow answer:
https://stackoverflow.com/questions/4692626/is-jdk-upward-or-backward-compatible

[caj411]

Thank you. I'll just install JRE 17 to solve the issue.
edit
Installing Java 17 solved the issue.