diff -r b6bca0666c38 -r 4fb5e6499da9 src/Pure/Tools/scala_project.scala
--- a/src/Pure/Tools/scala_project.scala	Mon Nov 20 15:55:10 2023 +0100
+++ b/src/Pure/Tools/scala_project.scala	Mon Nov 20 19:52:46 2023 +0100
@@ -11,7 +11,7 @@
 object Scala_Project {
   /** build tools **/
 
-  val java_version: String = "17"
+  val java_version: String = "21"
   val scala_version: String = "3.3.0"
 
   abstract class Build_Tool {