Android :: Create Files Hierarchy '/data/data/pkg/files' Directory

I try to create 'foo/bar.txt' in Android's /data/data/pkg/files directory.

It seems to be a contradiction in docs:

To write to a file, call Context.openFileOutput() with the name and path.

http://developer.android.com/guide/topics/data/data-storage.html#files

The name of the file to open; can not contain path separators.

[url]

And when I call

this.openFileOutput("foo/bar.txt", Context.MODE_PRIVATE);

exception is thrown:

java.lang.IllegalArgumentException: File foo/bar.txt contains a path separator

So how do I create file in subfolder?