src/java.base/share/classes/java/lang/ref/Finalizer.java

@@ -28,10 +28,13 @@
 import java.security.PrivilegedAction;
 import java.security.AccessController;
 import sun.misc.JavaLangAccess;
 import sun.misc.SharedSecrets;
 import sun.misc.VM;
+import java.util.TreeMap;
+import java.util.Set;
+import java.util.Map;
 
 final class Finalizer extends FinalReference<Object> { /* Package-private; must be in
                                                           same package as the Reference
                                                           class */
 

@@ -85,10 +88,40 @@
     /* Invoked by VM */
     static void register(Object finalizee) {
         new Finalizer(finalizee);
     }
 
+    static String printFinalizationQueue() {
+        Finalizer tmp = unfinalized;
+        Map <String, Integer> countMap = new TreeMap<String, Integer>();
+        synchronized (lock) {
+           while(tmp != null) {
+              Object referent = tmp.get();
+              if (referent != null) {
+                  Class<?> objClass = referent.getClass();
+                  String className = objClass.getName();
+                  Integer cnt = countMap.get(className);
+                  if (cnt == null) {
+                      countMap.put(className,1);
+                  }
+                  else {
+                      countMap.put(className,cnt + 1);
+                  }
+              }
+              tmp = tmp.next;
+           }
+        }
+
+        StringBuilder sb = new StringBuilder();
+        Set<String> keys = countMap.keySet();
+        for (String key : keys) {
+            sb.append("Class: " + key + " count: "  + countMap.get(key) + "\n");
+        }
+
+        return sb.toString();
+    }
+
     private void runFinalizer(JavaLangAccess jla) {
         synchronized (this) {
             if (hasBeenFinalized()) return;
             remove();
         }