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

*** 25,34 ****
--- 25,38 ----
  
  package java.lang.ref;
  
  import java.security.PrivilegedAction;
  import java.security.AccessController;
+ import java.util.Arrays;
+ import java.util.HashMap;
+ import java.util.Map;
+ 
  import sun.misc.JavaLangAccess;
  import sun.misc.ManagedLocalsThread;
  import sun.misc.SharedSecrets;
  import sun.misc.VM;
  
*** 184,193 ****
--- 188,220 ----
                      }
                      f.runFinalizer(jla);
                  }}});
      }
  
+     static String printFinalizationQueue() {
+         Map<String, int[]> countMap = new HashMap<>();
+         queue.forEach(r -> {
+             Object referent = r.get();
+             if (referent != null) {
+                 countMap.computeIfAbsent(
+                     referent.getClass().getName(), k -> new int[1])[0]++;
+             }
+         });
+         @SuppressWarnings("unchecked")
+         Map.Entry<String, int[]>[] entries = countMap.entrySet().toArray(
+             new Map.Entry[countMap.size()]
+         );
+         Arrays.sort(entries, (e1, e2) ->
+             Integer.compare(e2.getValue()[0], e1.getValue()[0]));
+         StringBuilder sb = new StringBuilder();
+         for (Map.Entry<String, int[]> e : entries) {
+             sb.append("Class: ").append(e.getKey())
+               .append(" count: ").append(e.getValue()[0]).append("\n");
+         }
+         return sb.toString();
+     }
+ 
      private static class FinalizerThread extends ManagedLocalsThread {
          private volatile boolean running;
          FinalizerThread(ThreadGroup g) {
              super(g, "Finalizer");
          }