xFilterManager.appendFilter("OpenDocument Text", "writer8");
// choose the template that defines the capabilities of the filepicker dialog
XInitialization xInitialize = (XInitialization) UnoRuntime.queryInterface(XInitialization.class, xFilePicker);
Short[] listAny = new Short[] { new Short(com.sun.star.ui.dialogs.TemplateDescription.FILESAVE_AUTOEXTENSION)};
xInitialize.initialize(listAny);
// add a control to the dialog to add the extension automatically to the filename...
XFilePickerControlAccess xFilePickerControlAccess = (XFilePickerControlAccess) UnoRuntime.queryInterface(XFilePickerControlAccess.class, xFilePicker);
xFilePickerControlAccess.setValue(com.sun.star.ui.dialogs.ExtendedFilePickerElementIds.CHECKBOX_AUTOEXTENSION, (short) 0, new Boolean(true));