code: private synchronized void clean() {
  		
  		while (checkOverFlow()) {
  
  			List<CacheObject> cacheObjectList = sort();
  
  			if (cacheObjectList != null && cacheObjectList.size() > 0) {
  				CacheObject cacheObject = (CacheObject) cacheObjectList.get(0);
  				remove(cacheObject.getKey());
  			}
  		}
  	}
docs: /*
  根据预设的缓存清理策略进行缓存清理