/** Sets the next entry in the write queue. */
  void setNextInWriteQueue(ReferenceEntry<K, V> next);

  /** Returns the previous entry in the write queue. */
  ReferenceEntry<K, V> getPreviousInWriteQueue();

  /** Sets the previous entry in the write queue. */
  void setPreviousInWriteQueue(ReferenceEntry<K, V> previous);

    // implements Queue

    @Override
    public boolean offer(ReferenceEntry<K, V> entry) {
      // unlink
      connectWriteOrder(entry.getPreviousInWriteQueue(), entry.getNextInWriteQueue());

      // add to tail
      connectWriteOrder(head.getPreviousInWriteQueue(), entry);
      connectWriteOrder(entry, head);

      return true;
    }

    @CheckForNull
    @Override

      this.nextWrite = next;
    }

    private ReferenceEntry<K, V> previousWrite = nullEntry();

    @Override
    public ReferenceEntry<K, V> getPreviousInWriteQueue() {
      return previousWrite;
    }

    @Override
    public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
      this.previousWrite = previous;
    }
  }

      this.nextWrite = next;
    }

    private ReferenceEntry<K, V> previousWrite = nullEntry();

    @Override
    public ReferenceEntry<K, V> getPreviousInWriteQueue() {
      return previousWrite;
    }

    @Override
    public void setPreviousInWriteQueue(ReferenceEntry<K, V> previous) {
      this.previousWrite = previous;
    }
  }