Separate version file

src/main/java/university/at/jku/ce/model/Version.java

+package university.at.jku.ce.model;
+
+public class Version {
+  private final static String VERSION_NUMBER = "2.0";
+
+  public static String getVersion(){
+    return VERSION_NUMBER;
+  }
+}

src/main/java/university/at/jku/ce/resource/VersionResource.java

 package university.at.jku.ce.resource;
 
 import university.at.jku.ce.exception.ExceptionParam;
+import university.at.jku.ce.model.Version;
 
 import javax.annotation.security.PermitAll;
 import javax.ws.rs.GET;
@@ -18,7 +19,7 @@ public class VersionResource {
 	public Response getUsers(@Context HttpHeaders headers) {
 		ExceptionParam.setMediaType(headers.getMediaType());
 		HashMap<String, String> versionNumber = new HashMap<>();
-		versionNumber.put("version", "2.0");
+		versionNumber.put("version", Version.getVersion());
 		GenericEntity<HashMap<String, String>> entity = new GenericEntity<HashMap<String, String>>(versionNumber) {
 		};
 		return Response.ok(entity).build();