apacheGH-2787: Use lazy holder pattern for system initialization

jena-core/src/main/java/org/apache/jena/sys/JenaSystem.java

@@ -76,24 +76,27 @@ public static void logLifecycle(String fmt, Object ...args) {
         System.err.println() ;
     }
 
-    public static void init() {
-        // Once jena is initialized, all calls are an immediate return.
-        if ( initialized )
-            return ;
-        // Overlapping attempts to perform initialization will block on the synchronized.
-        synchronized(JenaSystem.class) {
-            if ( initialized )
-                return ;
+    private static class LazyInitializer {
+        static final boolean IS_INITIALIZED = jenaSystemInitialization();
+
+        private static boolean jenaSystemInitialization() {
+            JenaSystem.initialized = true; // Set early to avoid blocking on static initialization.
             setup();
             if ( DEBUG_INIT )
                 singleton.debug(DEBUG_INIT);
             singleton.initialize();
             singleton.debug(false);
-            // Last so overlapping initialization waits on the synchronized
-            initialized = true;
+            return true;
         }
     }
 
+    public static void init() {
+        if ( initialized )
+            return ;
+        // Access the initialized flag to trigger class loading
+        var unused = LazyInitializer.IS_INITIALIZED;
+    }
+
     public static void shutdown() { singleton.shutdown(); }
 
     /** The level 0 subsystem - inserted without using the Registry load function.