Use jdk16 instead of jdk17 since jdk17 is not yet available at AppVeyor
diff --git a/appveyor.yml b/appveyor.yml
index bf15cbc..492090d 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -39,7 +39,7 @@
 environment:
   matrix:
     - JAVA_HOME: C:\Program Files\Java\jdk1.8.0
-    - JAVA_HOME: C:\Program Files\Java\jdk17
+    - JAVA_HOME: C:\Program Files\Java\jdk16
 build_script:
   - ./gradlew assemble javadoc
 test_script: