You should be able to create a Path
from System.getProperty("user.home")
which is the user's home directory
Something like...
Path path = FileSystems.getDefault().getPath(System.getProperty("user.home"));
Updated
JFileChooser
uses FileSystemView
to obtain it's "default" directory
Path path = FileSystemView.getFileSystemView().getDefaultDirectory().toPath()
Equally, you could also use something like...
Path docs = FileSystems.getDefault().getPath(System.getProperty("user.home"), "Documents");
Path myDocs = FileSystems.getDefault().getPath(System.getProperty("user.home"), "My Documents");
Path userHome = FileSystems.getDefault().getPath(System.getProperty("user.home"));
And test each to see if they actually exist