Install libopenjfx-java by entering the following commands in the terminal:
sudo apt update sudo apt install libopenjfx-java
JavaFX/OpenJFX 8 - Rich client application platform for Java (Java libraries)
JavaFX/OpenJFX is a set of graphics and media APIs that enables Java developers to design, create, test, debug, and deploy rich client applications that operate consistently across diverse platforms. . This package contains the Java libraries only, installing it won't add the JavaFX classes to the default classpath automatically. The integration with the JRE is provided by the openjfx package.