code: public void clearExpired() {
  		Iterator keys = cacheLineTable.keySet().iterator();
  
  		while (keys.hasNext()) {
  			Object key = keys.next();
  
  			if (hasExpired(key)) {
  				removeObject(key);
  			}
  		}
  	}
docs: Clears all expired cache entries; also clear any cache entries where the
  SoftReference in the CacheLine object has been cleared by the gc