Java 27 and 26: runnable demos and captured output for every JEP, plus version lanes

Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
2026-09-21 15:08:50 +00:00
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+# JVM options that JDK 27 removed or renamed. Each runs 'java <option> -version' on 26 and on 27.
+
+=== -noverify
+  JDK 26:
+    OpenJDK 64-Bit Server VM warning: Options -Xverify:none and -noverify were deprecated in JDK 13 and will likely be removed in a future release.
+    OpenJDK 64-Bit Server VM Corretto-26.0.2.11.1 (build 26.0.2.1+11-FR, mixed mode, sharing)
+  JDK 27:
+    Unrecognized option: -noverify
+    Error: Could not create the Java Virtual Machine.
+
+=== -Xverify:none
+  JDK 26:
+    OpenJDK 64-Bit Server VM warning: Options -Xverify:none and -noverify were deprecated in JDK 13 and will likely be removed in a future release.
+    OpenJDK 64-Bit Server VM Corretto-26.0.2.11.1 (build 26.0.2.1+11-FR, mixed mode, sharing)
+  JDK 27:
+    Unrecognized verification option: -Xverify:none
+    Error: Could not create the Java Virtual Machine.
+
+=== -noclassgc
+  JDK 26:
+    Warning: -noclassgc option is deprecated and may be removed in a future release.
+    OpenJDK 64-Bit Server VM Corretto-26.0.2.11.1 (build 26.0.2.1+11-FR, mixed mode, sharing)
+  JDK 27:
+    Unrecognized option: -noclassgc
+    Error: Could not create the Java Virtual Machine.
+
+=== -XX:+UseCompressedClassPointers
+  JDK 26:
+    OpenJDK 64-Bit Server VM warning: Option UseCompressedClassPointers was deprecated in version 25.0 and will likely be removed in a future release.
+    OpenJDK 64-Bit Server VM Corretto-26.0.2.11.1 (build 26.0.2.1+11-FR, mixed mode, sharing)
+  JDK 27:
+    OpenJDK 64-Bit Server VM warning: Ignoring option UseCompressedClassPointers; support was removed in 27.0
+    OpenJDK 64-Bit Server VM Corretto-27.0.0.35.1 (build 27+35-FR, mixed mode, sharing)
+
+=== -XX:InitiatingHeapOccupancyPercent=40
+  JDK 26:
+    OpenJDK 64-Bit Server VM Corretto-26.0.2.11.1 (build 26.0.2.1+11-FR, mixed mode, sharing)
+  JDK 27:
+    OpenJDK 64-Bit Server VM warning: Option InitiatingHeapOccupancyPercent was deprecated in version 27.0 and will likely be removed in a future release. Use option G1IHOP instead.
+    OpenJDK 64-Bit Server VM Corretto-27.0.0.35.1 (build 27+35-FR, mixed mode, sharing)
+
+=== -XX:G1IHOP=40
+  JDK 26:
+    Unrecognized VM option 'G1IHOP=40'
+    Error: Could not create the Java Virtual Machine.
+  JDK 27:
+    OpenJDK 64-Bit Server VM Corretto-27.0.0.35.1 (build 27+35-FR, mixed mode, sharing)
+
+=== -XX:+UnlockExperimentalVMOptions -XX:+UseGraalJIT   (JVMCI and the Graal JIT hook were removed in 27)
+  JDK 26:
+    Cannot use JVMCI compiler: JVMCI compiler 'graal' specified by jvmci.Compiler not found
+  JDK 27:
+    Unrecognized VM option 'UseGraalJIT'
+    Error: Could not create the Java Virtual Machine.