So if you download javafx samples and demos and run ensemble it seems to work just fine at first. Go to Web > HTML Editor however and you’ll encounter error. What to do? We have source, lets build it from source. Only problem is you will get various errors. Net search will tell you to clean and build. What do we lose? Only you encounter another error. Properties > Libraries > Manage platform > Add platform. Use that platform. Comment out 107 to 110 to run HTML Editor.