why don't print in console with println?

@SpringBootApplication
public class Demo10Application {

  public Demo10Application(DemoProperties demoProperties) {
    this.demoProperties = demoProperties;
  }

    public static void main(String[] args) {
        SpringApplication.run(Demo10Application.class, args);
    }


     @Autowired
     private DemoProperties demoProperties;

        public void printDemoProperties() {
        System.out.println("Username: " + demoProperties.getUsername());
        System.out.println("Password: " + demoProperties.getPassword());
        System.out.println("Email Address: " + demoProperties.getEmail());
    }
}