code: @Override
    public FSDataOutputStream create(Path f, FsPermission permission,
      boolean overwrite,
      int bufferSize, short replication, long blockSize,
      Progressable progress) throws IOException {
  
      FSDataOutputStream fd = new FSDataOutputStream(
                                  new CacheOutputStream(conf, this, f,
                                      permission, overwrite, bufferSize,
                                      replication, blockSize, progress));
  
      return fd;
    }
docs: Create new file. We start writing the data into underlying
  filessystem as well as the cacheFileSystem.