code: public void move(Path srcDirFilePath, Path dstDirFilePath) {
  		String id = ids.getIfPresent(srcDirFilePath);
  		if (id != null) {
  			ids.put(dstDirFilePath, id);
  			ids.invalidate(srcDirFilePath);
  		}
  	}
docs: Transfers ownership from the id currently associated with <code>srcDirFilePath</code> to <code>dstDirFilePath</code>. Usefule during folder move operations.
  This method has no effect if the content of the source dirFile is not currently cached.
  
  @param srcDirFilePath The dirFile that contained the cached id until now.
  @param dstDirFilePath The dirFile that will contain the id from now on.