Install ecj by entering the following commands in the terminal:
sudo apt update sudo apt install ecj
Description:
standalone version of the Eclipse Java compiler
This package provides a standalone version of the Eclipse JDT compiler which is distributed as part of Eclipse. It passes the JCK (Java Compatibility Kit) and is compatible with Java 1.3, 1.4, 5, 6, 7, 8 and 9.
Homepage: http://www.eclipse.org/jdt/core/index.php
Version: 3.13.3-1
Section: universe/devel