I've followed the directions. created a subfolder named "data" in the saved sketch folder. Made sure the serial monitor is closed. Installed the ESP8266 Data Upload tool in the correct place. It shows up on the Tools menu.
I keep getting a JAVA error in the IDE window:
Exception in thread "AWT-EventQueue-0" java.lang.NoSuchMethodError: processing.app.BaseNoGui.getBuildFolder()Ljava/io/File;
Create a new sketch, save it, create the data folder, add index.html to that, try again, same result.
I'm obviously missing something but what is it? Any tips or suggestions would be great.