private static String inputStreamToString(InputStream in) throws IOException {
    return Util.readFully(new InputStreamReader(in, Util.UTF_8));
  }
Closes the cache and deletes all of its stored values. This will delete
all files in the cache directory including files that weren't created by
the cache.
core/src/main/java/com/bumptech/glide/disklrucache/DiskLruCache.java