The Javadoc of FileSystemOptions currently says:
Container for FileSystemOptions.
You have to use *FileSystemConfigBuilder.getInstance() to fill this container
The first sentence contains no helpful information at all. It should explain that any file system can be configured and illustrate a typical usage using a small code example.
I think the documentation should look like this:
File systems can be configured individually using these options.
To configure a file system, you set certain properties in a FileSystemOptions object. Most filesystems provide a FileSystemConfigBuilder that knows the specific options of the file system.
To use the options, they have to be passed to the FileSystemManager.resolveFile() method. From there, the options apply to all files that are resolved relative to that file.
These few sentences would have helped me a lot in understanding.