ReferenceQueue expunge

import java.lang.ref.*;

public class Expunger{
  public static interface Cleaner<T, Ref extends Reference<? extends T>>{
    void clean(Ref ref);
  }

  public static <T, Ref extends Reference<? extends T>> void expunge(Cleaner<T, Ref> cleaner, final ReferenceQueue<T> queue, int expungeThreshold){
    Reference<? extends T> w=queue.poll();
    if (w==null)
      return;//keep the method short, so it's inlined; queue being empty is the fast lane

    expungeImpl(cleaner, w, queue, expungeThreshold);
  }

  static <T, Ref extends Reference<? extends T>> void expungeImpl(final Cleaner<T, Ref> cleaner, Reference<? extends T> ref, final ReferenceQueue<T> queue, int expungeThreshold){
    expunge(cleaner, ref);
    for (;--expungeThreshold>0  && null!=(ref=queue.poll());){
      expunge(cleaner, ref);
    }
    if (expungeThreshold==0){//delegate a full expunge to the finalizer
      //the anon. class stores cleaner and queue in fields, and the c-tor has happens before with finalize() unlike any other method...
      new Object(){//feel free to extend WeakRefence(cleaner) and also keep weak ref to queue useful for non-native resources
        protected void finalize(){//keep in mind: the execution of cleaner.clean(Ref) will not have the right ContextClassLoader, ThreadGroup, AccessControlContext
          expunge(cleaner, queue, Integer.MAX_VALUE);
        }
      };
    }
  }

  @SuppressWarnings("unchecked")
  private static <T, Ref extends Reference<? extends T>> void expunge(Cleaner<T, Ref> cleaner, Reference<? extends T> ref){
    cleaner.clean((Ref) ref);
  }
}