code: public void invalidateCache(String key) {
          if (DEBUG) {
              CLog.d(LOG_TAG, "key: %s, invalidateCache", key);
          }
          try {
              mFileCache.getDiskCache().delete(key);
          } catch (IOException e) {
              if (DEBUG) {
                  e.printStackTrace();
              }
          }
          mMemoryCache.remove(key);
      }
docs: delete cache by key
  
  @param key