author Theetouch Kasemarnontana old repository has issues about pushing codes
a graphical unit converter for length units.
If you are using JDK 8-10 then JavaFX is included. You don't need to add any libraries.
If you are using Java JDK 11, then install JavaFX 11 from https://gluonhq.com/products/javafx.
Also for JDK 11, to add JavaFX to a project in your IDE see: https://openjfx.io/openjfx-docs/