[Spring] Spotbugs static class and default encoding (#2609)

* add static modifier - mvn verify passes

* specify charset, mvn verify works, compiles and clean on spotbugs in my project

* update samples as per contribution guide; mvn integration-test passes

* commit rest of samples

* fix missing newline at EOF

* lots of new newlines

* needed to run mvn clean beforehand...

samples/server/petstore/springboot-beanvalidation/src/main/java/org/openapitools/OpenAPI2SpringBoot.java

@@ -27,7 +27,7 @@ public class OpenAPI2SpringBoot implements CommandLineRunner {
         new SpringApplication(OpenAPI2SpringBoot.class).run(args);
     }
 
-    class ExitException extends RuntimeException implements ExitCodeGenerator {
+    static class ExitException extends RuntimeException implements ExitCodeGenerator {
         private static final long serialVersionUID = 1L;
 
         @Override

samples/server/petstore/springboot-beanvalidation/src/main/java/org/openapitools/api/ApiUtil.java

@@ -16,4 +16,4 @@ public class ApiUtil {
             throw new RuntimeException(e);
         }
     }
-}
+}