Windows 64 install help

[RnBrgn]

echo 'println("Hello")' | scala-cli -
Compiling project (Scala 3.8.3, JVM (8))
Error: 8 is not a valid choice for -java-output-version
scalac -help gives more information
Error compiling project (Scala 3.8.3, JVM (8))
Compilation failed

C:\Users>java -version
java version "26" 2026-03-17
Java(TM) SE Runtime Environment (build 26+35-2893)
Java HotSpot(TM) 64-Bit Server VM (build 26+35-2893, mixed mode, sharing)

[Yahan-Botheju]

🛠️ Scala CLI Java Version Error (Windows) - Fix Guide

❌ Problem

Running:

echo 'println("Hello")' | scala-cli -

fails with:

Error: 8 is not a valid choice for -java-output-version

Even though Java is installed:

java -version
java version "26"

---

🧠 Root Cause

entity["software","scala-cli","Scala command line tool"] is trying
to compile using Java 8 bytecode target, but the installed Java
version (Java 26) is not compatible with that configuration.

This causes a mismatch between: - Scala CLI default target (Java 8) -
Installed JDK version (Java 26)

---

✅ Solutions

✔️ Option 1 (Recommended): Use Java LTS (17 or 21)

Install Java 17 or Java 21, then run:

scala-cli --jvm 17 -

or

scala-cli --jvm 21 -

---

✔️ Option 2: Set JAVA_HOME

Set environment variable:

JAVA_HOME = path-to-jdk-17-or-21

Then restart terminal.

---

✔️ Option 3: Explicit JVM path

scala-cli --java-home "C:\Program Files\Java\jdk-17" -

---

🎯 Result

After fixing: - Compilation works ✔️ - No java-output-version error ✔️ -
Scala program runs successfully ✔️

---

💡 Recommendation

For Scala development: - Use Java 17 or Java 21 (LTS) - Avoid very
new Java versions with older tool defaults

---

🚀 Summary

This is a tooling compatibility issue, not a code issue.