[Win10] Installation Error - Unsupported class file major version 64

[I-Knight-I]

The install is failing when trying to build MCP-Reborn. The settings.gradle for it apparently uses Java 20.

Snippet of the error:

System Info:

Windows 10
WSL 1 (bash installed correctly)
32GB DDR4 RAM
Python 3.12.10
PIP 25.0.1

Java Attempts (All Failed)

0. WSL: No JDK
   Windows: Oracle JDK 21
   Log: "Failed to find java / javac"

1. WSL: OpenJDK 8
   Windows: OpenJDK 8
   Log: log-jdk8-8.txt

2. WSL: OpenJDK 21
   Windows: Oracle JDK 20
   Log: log-jdk21-20.txt

3. WSL: OpenJDK 21.0.7
   Windows: Oracle JDK 21.0.5
   Log: log-jdk21-21.txt

[I-Knight-I]

Identified the fix thanks to this comment: #791 (comment)

On Windows, make sure that JAVA_HOME is set to JDK 1.8 in BOTH your System-wide environment variables AND User environment variables.

It could be worth adding these prerequisite checks directly to the setup.py script so that the error output is more useful to the user.

---

Now to figure out why I'm getting a new error:
pip._vendor.pyproject_hooks._impl.BackendUnavailable: Cannot import 'setuptools.build_meta'

[Miffyli]

Sorry for the delayed reply! Good you found the solution; indeed you need to make sure right java is running in all involved envs. A check for this would be a welcomed addition! :)

pip._vendor.pyproject_hooks._impl.BackendUnavailable: Cannot import 'setuptools.build_meta'

Hard to say with more context, but setuptools errors are usually related to having old packages (e.g., gym) and newer Python versions.