# JDK: openjdk version "25.0.5" 2026-10-20 LTS
$ javac --release 25 ScopeProbe.java
ScopeProbe.java:1: error: StructuredTaskScope is a preview API and is disabled by default.
import java.util.concurrent.StructuredTaskScope;
                           ^
  (use --enable-preview to enable preview APIs)
ScopeProbe.java:6: error: StructuredTaskScope is a preview API and is disabled by default.
        try (var scope = StructuredTaskScope.open()) {
                         ^
  (use --enable-preview to enable preview APIs)
2 errors
$ javac --release 25 --enable-preview ScopeProbe.java
Note: ScopeProbe.java uses preview features of Java SE 25.
Note: Recompile with -Xlint:preview for details.
$ java -cp preview-classes ScopeProbe
Error: LinkageError occurred while loading main class ScopeProbe
	java.lang.UnsupportedClassVersionError: Preview features are not enabled for ScopeProbe (class file version 69.65535). Try running with '--enable-preview'
$ java --enable-preview -cp preview-classes ScopeProbe
security: ok | performance: ok