Make sure you have Java and Maven installed. Also, install the Heroku CLI.
$ git clone https://github.com/heroku/java-getting-started.git
$ cd java-getting-started
$ mvn install
$ heroku local:startYour app should now be running on localhost:5000.
If you're going to use a database, ensure you have a local .env file that reads something like this:
DATABASE_URL=postgres://localhost:5432/java_database_name
$ heroku create
$ git push heroku master
$ heroku open