取消计时器

我已经实现了一个分配固定数量令牌的令牌系统。分配时的每个令牌都会启动一个计时器,该计时器将在几分钟后过期,并清除令牌槽以供重用。如果用户在计时器到期前验证令牌,则应取消计时器并用另一个令牌有效期重置。我似乎无法从计时器线程之外取消计时器,这是预期的行为。代码段如下:

/**
 * Fills one of the available slots with a new session key
 * @param sessionKey
 * @return true on slot fill success - false on fail
 */
public boolean fillSlot(String sessionKey)
{
    if(count<MAXCOUNT)
    {
        //Add key to slot
        slots.add(sessionKey);
        //Up the key count
        upCount();
        //Set up expiry timer
        Timer timer = new Timer();
        timer.schedule(new ExpiringTokentask(timer,sessionKey), EXPIRY_TIME);
        timers.put(sessionKey, timer);
        return true;
    }
    return false;
}

    /**
 * Check if a given key is stored in the slots
 * reset timer every time key is checked
 * @param sessionKey
 * @return true on key found false on not found
 */
public boolean checkSlot(String sessionKey)
{
    //TODO: More efficient key search and storage for larger user sets
    //TODO: Upgrade from memory array to h2 embedded DB
    for(int i=0;i<slots.size();i++)
    {
        if(sessionKey.equals(slots.get(i)))
        {
            //Reset timer
            Timer timer = timers.get(sessionKey);
            //Can't seem to do this
            // timer.cancel();
            timer.schedule(new ExpiringTokentask(timer,sessionKey), EXPIRY_TIME);
            //Return token validation
            return true;
        }
    }

    return false;
}


private class ExpiringTokentask extends TimerTask
{
    private Timer timer;
    private String expireToken;

    public ExpiringTokentask(Timer timer, String sessionKey)
    {
        this.timer = timer;
        this.expireToken = sessionKey;
        System.out.println(sessionKey);
    }

    public void run() {
        System.out.format("Time's up!%n");
        clearSlot(expireToken);
        timer.cancel(); //Terminate the timer thread
    }
}