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private TreeTableView buildFileBrowserTreeTableView() {
    // create a simple String treeview
    TreeItem<File> root = createNode(new File("/"));
    root.setExpanded(true);

    final TreeTableView<File> treeTableView = new TreeTableView<File>();
    treeTableView.setShowRoot(true);
    treeTableView.setRoot(root);

    // --- name column
    TreeTableColumn<File, String> nameColumn = new TreeTableColumn<File, String>("Name");
    nameColumn.setPrefWidth(300);
    nameColumn.setCellValueFactory(new Callback<CellDataFeatures<File, String>, ObservableValue<String>>() {
        @Override public ObservableValue<String> call(CellDataFeatures<File, String> p) {
            File f = p.getValue().getValue();
            String text = f.getParentFile() == null ? "/" : f.getName();
            return new ReadOnlyObjectWrapper<String>(text);
        }
    });
    // temporary cell factory to simulate expand / collapse instructions
    nameColumn.setCellFactory(new Callback<TreeTableColumn<File, String>, TreeTableCell<File, String>>() {
        @Override public TreeTableCell<File, String> call(TreeTableColumn<File, String> p) {
            final TreeTableCell<File, String> cell = new TreeTableCell<File, String>() {
                @Override protected void updateItem(String item, boolean empty) {
                    super.updateItem(item, empty);
                    if (empty || item == null) {
                        setText(null);
                    } else {
                        setText(item);
                    }
                }
            };
            return cell;
        }
    });

    // --- size column
    TreeTableColumn<File, File> sizeColumn = new TreeTableColumn<File, File>("Size");
    sizeColumn.setPrefWidth(100);
    sizeColumn.setCellValueFactory(new Callback<CellDataFeatures<File, File>, ObservableValue<File>>() {
        @Override public ObservableValue<File> call(CellDataFeatures<File, File> p) {
            return new ReadOnlyObjectWrapper<File>(p.getValue().getValue());
        }
    });
    sizeColumn.setCellFactory(new Callback<TreeTableColumn<File, File>, TreeTableCell<File, File>>() {
        @Override public TreeTableCell<File, File> call(final TreeTableColumn<File, File> p) {
            return new TreeTableCell<File, File>() {
                @Override protected void updateItem(File item, boolean empty) {
                    super.updateItem(item, empty);

                    TreeTableView treeTable = p.getTreeTableView();

                    // if the File is a directory, it has no size...
                    if (getIndex() >= treeTable.impl_getTreeItemCount()) {
                        setText(null);
                    } else {
                        TreeItem<File> treeItem = treeTable.getTreeItem(getIndex());
                        if (item == null || empty || treeItem == null || 
                                treeItem.getValue() == null || treeItem.getValue().isDirectory()) {
                            setText(null);
                        } else {
                            setText(nf.format(item.length()) + " KB");
                        }
                    }
                }
            };
        }
    });
    sizeColumn.setComparator(new Comparator<File>() {
        @Override public int compare(File f1, File f2) {
            long s1 = f1.isDirectory() ? 0 : f1.length();
            long s2 = f2.isDirectory() ? 0 : f2.length();
            long result = s1 - s2;
            if (result < 0) {
                return -1;
            } else if (result == 0) {
                return 0;
            } else {
                return 1;
            }
        }
    });

    // --- modified column
    TreeTableColumn<File, Date> lastModifiedColumn = new TreeTableColumn<File, Date>("Last Modified");
    lastModifiedColumn.setPrefWidth(130);
    lastModifiedColumn.setCellValueFactory(new Callback<CellDataFeatures<File, Date>, ObservableValue<Date>>() {
        @Override public ObservableValue<Date> call(CellDataFeatures<File, Date> p) {
            return new ReadOnlyObjectWrapper<Date>(new Date(p.getValue().getValue().lastModified()));
        }
    });
    lastModifiedColumn.setCellFactory(new Callback<TreeTableColumn<File, Date>, TreeTableCell<File, Date>>() {
        @Override public TreeTableCell<File, Date> call(TreeTableColumn<File, Date> p) {
            return new TreeTableCell<File, Date>() {
                @Override protected void updateItem(Date item, boolean empty) {
                    super.updateItem(item, empty);

                    if (item == null || empty) {
                        setText(null);
                    } else {
                        setText(df.format(item));
                    }
                }
            };
        }
    });

    treeTableView.getColumns().setAll(nameColumn, sizeColumn, lastModifiedColumn);

    return treeTableView;
}

private TreeItem<File> createNode(final File f) {
    final TreeItem<File> node = new TreeItem<File>(f) {
        private boolean isLeaf;
        private boolean isFirstTimeChildren = true;
        private boolean isFirstTimeLeaf = true;

        @Override
        public ObservableList<TreeItem<File>> getChildren() {
            if (isFirstTimeChildren) {
                isFirstTimeChildren = false;
                super.getChildren().setAll(buildChildren(this));
            }
            return super.getChildren();
        }

        @Override
        public boolean isLeaf() {
            if (isFirstTimeLeaf) {
                isFirstTimeLeaf = false;
                File f = (File) getValue();
                isLeaf = f.isFile();
            }

            return isLeaf;
        }
    };
    return node;
}

private ObservableList<TreeItem<File>> buildChildren(TreeItem<File> TreeItem) {
    File f = (File) TreeItem.getValue();
    if (f != null && f.isDirectory()) {
        File[] files = f.listFiles();
        if (files != null) {
            ObservableList<TreeItem<File>> children = FXCollections.observableArrayList();

            for (File childFile : files) {
                children.add(createNode(childFile));
            }

            return children;
        }
    }

    return FXCollections.emptyObservableList();
}