Marker class should be static

api/src/main/java/jakarta/el/ELResolver.java

diff --git a/api/src/main/java/jakarta/el/ELResolver.java b/api/src/main/java/jakarta/el/ELResolver.java
index 9f0ea7a..c3d7eed 100644
--- a/api/src/main/java/jakarta/el/ELResolver.java
+++ b/api/src/main/java/jakarta/el/ELResolver.java
@@ -278,7 +278,7 @@
      *
      * @since Jakarta Expression Language 6.1
      */
-    public class StandaloneIdentifierMarker {
+    public static class StandaloneIdentifierMarker {
 
         private StandaloneIdentifierMarker() {
             // Non-public default constructor as there is no need to create instances of this class.