JAVA muon data processing program on Windows 10 causes “UnsupportedClassVersionError”.

The key part of the error is:

UnsupportedClassVersionError

...has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

This means:

  • Class file version 55 = Java 11
  • Class file version 52 = Java 8

So you are trying to run a program that was compiled with Java 11, but your PC only has Java 8 installed.

Check your Java version

Open a Command Prompt and type:

java -version

I expect you’ll see something like:

java version "1.8.0_xxx"

Fix

Install a Java Runtime or JDK version 11 or later (Java 17 or Java 21 will also run Java 11 programs in most cases).

Then check:

java -version

It should report something like:

openjdk version "17..."

or

java version "11..."

If you already installed Java 11+

Windows may still be using the old Java 8. Check:

where java

If you see something like

C:\Program Files\Java\jre1.8...

before the new installation, your PATH needs updating.

By Admin

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