javafx 8 - JavaFX8 TreeTableView multiple root items -

treeitem<filemodel> root = new treeitem<filemodel>(playlist); treetblviewfiles.setroot(root); treetblviewfiles.setshowroot(true); 

the code above sets 1 root item, need have several called root items expandable list of child items. how do that?
in advance.

you make parent root, don't show.

that parent's children may roots, show.