Added a few comments to server java files

Server/src/main/java/hello/Application.java

@@ -3,9 +3,11 @@ package hello;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
+//application to boot with spring
 @SpringBootApplication
 public class Application {
 
+    //run the application
     public static void main(String[] args) {
         SpringApplication.run(Application.class, args);
     }

Server/src/main/java/hello/GreetingController.java

@@ -13,6 +13,7 @@ public class GreetingController {
 
     @RequestMapping("/greeting")
     public Greeting greeting(@RequestParam(value="name", defaultValue="World") String name) {
+        //increment the id every time the page is refreshed (a new user visits the page)
         return new Greeting(counter.incrementAndGet(),
                             String.format(template, name));
     }