@CanIgnoreReturnValue
  public DirectoryEntry requireExists(Path pathForException) throws NoSuchFileException {
    if (!exists()) {
      throw new NoSuchFileException(pathForException.toString());
    }
    return this;
  }
Checks that this entry exists, throwing an exception if not.

@return this
@throws NoSuchFileException if this entry does not exist
jimfs/src/main/java/com/google/common/jimfs/DirectoryEntry.java