Download the .jar from: https://doclet.github.io/resources/bin/TeXDoclet.jar
Since JAXB is deprecated in Java 11 one has to use the Java 8 binaries to run the jar
/usr/lib/jvm/java-8-openjdk-amd64/bin/javadoc -docletpath <TeXDoclet.jar> \
-doclet org.stfm.texdoclet.TeXDoclet \
-noindex \
-tree \
-hyperref \
-private \
-output xml-project/doc-tex/main.tex \
-title "STPT: XML Technologies Project" \
-author "Alexandru Munteanu\\\\Maria Vonica\\\\Zouel Fikar Jahjah" \
-sourcepath /xml-project/src/main/java \
-subpackages models parsers core
The output is going to be in doc-tex/main.tex, compile it twice using pdflatex main.tex and enjoy!