Introduce constants

Author: sven1103

user-interface/src/main/java/life/qbic/datamanager/views/demo/ComponentDemo.java

@@ -44,6 +44,8 @@
 public class ComponentDemo extends Div {
 
   public static final String HEADING_2 = "heading-2";
+  public static final String GAP_04 = "gap-04";
+  public static final String FLEX_VERTICAL = "flex-vertical";
   Div title = new Div("Data Manager - Component Demo");
 
   public ComponentDemo() {
@@ -95,7 +97,7 @@ private static Div fontsShowCase() {
     Div header = new Div("Body Font Styles");
     header.addClassName(HEADING_2);
     container.add(header);
-    container.addClassNames("flex-vertical", "gap-04");
+    container.addClassNames(FLEX_VERTICAL, GAP_04);
 
     Arrays.stream(BodyFontStyles.fontStyles).forEach(fontStyle -> {
       Div styleHeader = new Div();
@@ -133,7 +135,7 @@ private static Div stepperDialogShowCase(List<Step> steps, String dialogTitle) {
 
     content.add(title);
     content.add(showDialog);
-    content.addClassNames("flex-vertical", "gap-04");
+    content.addClassNames(FLEX_VERTICAL, GAP_04);
 
     Div confirmBox = new Div("Click the button and press 'Cancel' or 'Save'");
     dialog.registerConfirmAction(() -> {
@@ -212,7 +214,7 @@ private static Div dialogShowCase(AppDialog dialog, String dialogType) {
     });
 
     content.add(showDialog, confirmBox);
-    content.addClassNames("flex-vertical", "gap-04");
+    content.addClassNames(FLEX_VERTICAL, GAP_04);
     return content;
   }