Start by setting this up: 

<blockquote><pre>-bash-4.2$ tree
.
+-- <a href="step01/pom.xml.phps">pom.xml</a>
+-- src
    +-- main
        +-- java
        |   +-- com
        |       +-- example
        |           +-- demo
        |               +-- <a href="step01/src/main/java/com/example/demo/HomeController.java">HomeController.java</a>
        |               +-- <a href="step01/src/main/java/com/example/demo/SpringBoot01Application.java">SpringBoot01Application.java</a>
        +-- resources
            +-- templates
                +-- <a href="step01/src/main/resources/templates/index.html.phps">index.html</a>

8 directories, 4 files
-bash-4.2$ pwd
/u/dgerman/apache/htdocs/spring-boot/fall2019/step01
-bash-4.2$</pre></blockquote> 

From here on: 

<ol>
  <li> <code>mvn package</code> <p> 
  <li> <code>java -jar target/demo-0.0.1-SNAPSHOT.jar --server.port=31415</code>
</ol> 

<p> Again, use your own port (instead of using mine, shown).