* the type of the concrete implementation.
     */
    abstract S self();

    /** Drains the reference queues used by this segment, if any. */
    @GuardedBy("this")
    void maybeDrainReferenceQueues() {}

    /** Clears the reference queues used by this segment, if any. */
    void maybeClearReferenceQueues() {}

    /** Sets the value of the given {@code entry}. */