Hi Joey. Did you notice that ComboBox has the API that you can just set an array of items to it ?
eg.
String[] data = getDataForComboBox();
ComboBox<String> comboBox = new ComboBox<>();
comboBox.setItems(data); // this creates a list data provider internally, you don't need to do it yourself
comboBox.getDataProvider(); // this would return the DP if you need it for something