docs: public void setCacheDir(String dirName, int mode) {
          if (sDebug) {
              LogUtils.v(TAG, "setCacheDir() dirName=" + dirName + " mode=" + mode);
          }
          if (dirName == null) {
              mCacheDirName = DIR_NAME_DEFAULT;
          } else {
              mCacheDirName = dirName;
          }
          mMode = mode;
          checkCacheDir(true);
      }