I see you are using Jersey, you can explore the documentation on their website, there are many examples.
This page describes how to create a new REST API using a
maven archetype, it should take no more than 5 minutes, you can then analyze the code while reading the docs:
https://jersey.java.net/documentation/latest/getting-started.html
If later on you want to integrate Jersey with Spring and some data access, you can take a look at this boilerplate project
https://github.com/gastongr/rest-boilerplate. You can get that running locally in 5 minutes too.
Also if you like video lessons, take a look at this great free course
https://javabrains.io/courses/javaee_jaxrs