Lexical Analyser in java with Jflex and Antlr, for the language "fun", check Grammar and specifications about the language.pdf for language details.
Also you will need to set your path for antlr, in my case it was the command : export CLASSPATH=".:/usr/local/lib/antlr-4.5.1-complete.jar:./target/classes:$CLASSPATH"
This was done for the Formal Languages and compilators at EAFIT University.