src/java.base/share/classes/jdk/internal/ref/CleanerImpl.java

*** 155,164 ****
--- 155,184 ----
              }
          }
      }
  
      /**
+      * Processes next Cleanable that has been waiting in the queue.
+      *
+      * @return {@code true} if a Cleanable was found in the queue and
+      * was processed or {@code false} if the queue was empty.
+      */
+     public boolean cleanNextEnqueued() {
+         Cleanable ref = (Cleanable) queue.poll();
+         if (ref != null) {
+             try {
+                 ref.clean();
+             } catch (Throwable t) {
+                 // ignore exceptions from the cleanup action
+             }
+             return true;
+         } else {
+             return false;
+         }
+     }
+ 
+     /**
       * Perform cleaning on an unreachable PhantomReference.
       */
      public static final class PhantomCleanableRef extends PhantomCleanable<Object> {
          private final Runnable action;