if (currentFolder.isEmpty()) { // Exit BookmarksActivity if currently in the home folder.
NavUtils.navigateUpFromSameTask(this);
} else { // Navigate up one folder.
// Place the former parent folder in `currentFolder`.
currentFolder = bookmarksDatabaseHelper.getParentFolder(currentFolder);
if (currentFolder.isEmpty()) { // Exit BookmarksActivity if currently in the home folder.
NavUtils.navigateUpFromSameTask(this);
} else { // Navigate up one folder.
// Place the former parent folder in `currentFolder`.
currentFolder = bookmarksDatabaseHelper.getParentFolder(currentFolder);