A java demo project how to write a javadoc extension as a doclet. Or how to read custom javadoc tags.

The demo doclet code is in the class DocDoclet here:
https://github.com/tux2323/doclet-demo/blob/master/src/main/java/com/github/tux2323/doclet/DocDoclet.java

See also the test DocDocletTest how to run a doclet from a java application:
https://github.com/tux2323/doclet-demo/blob/master/src/test/java/com/github/tux2323/doclet/DocDocletTest.java