Adds tabbed panel method to hide tab if it is empty.

https://github.com/BentoBoxWorld/BentoBox/issues/896

src/main/java/world/bentobox/bentobox/api/commands/island/IslandSettingsCommand.java

@@ -47,6 +47,7 @@ public class IslandSettingsCommand extends CompositeCommand {
         .tab(2, new SettingsTab(getWorld(), user, island, Flag.Type.SETTING))
         .startingSlot(1)
         .size(54)
+        .hideIfEmpty()
         .build().openPanel();
         return true;
     }

src/main/java/world/bentobox/bentobox/api/panels/TabbedPanel.java

@@ -83,6 +83,11 @@ public class TabbedPanel extends Panel implements PanelListener {
         // Get the tab
         Tab tab = tpb.getTabs().get(activeTab);
 
+        // Remove any tabs that have no items, if required
+        if (tpb.isHideIfEmpty()) {
+            tpb.getTabs().values().removeIf(t -> !t.equals(tab) && !t.getPanelItems().stream().anyMatch(Objects::nonNull));
+        }
+
         // Set up the tabbed header
         setupHeader(tab, items);
 
@@ -127,7 +132,9 @@ public class TabbedPanel extends Panel implements PanelListener {
         // Add icons
         for (Entry<Integer, Tab> tabPanel : tpb.getTabs().entrySet()) {
             // Add the icon to the top row
-            if (tabPanel.getValue().getPermission().isEmpty() || tpb.getUser().hasPermission(tabPanel.getValue().getPermission()) || tpb.getUser().isOp()) {
+            if (tabPanel.getValue().getPermission().isEmpty()
+                    || tpb.getUser().hasPermission(tabPanel.getValue().getPermission())
+                    || tpb.getUser().isOp()) {
                 PanelItem activeIcon = tabPanel.getValue().getIcon();
                 // Set the glow of the active tab
                 activeIcon.setGlow(tabPanel.getValue().equals(tab));

src/main/java/world/bentobox/bentobox/api/panels/builders/TabbedPanelBuilder.java

@@ -22,6 +22,7 @@ public class TabbedPanelBuilder {
     private int startingSlot;
     private World world;
     private User user;
+    private boolean hideIfEmpty;
 
     /**
      * Forces panel to be a specific number of slots.
@@ -79,6 +80,14 @@ public class TabbedPanelBuilder {
         return this;
     }
 
+    /**
+     * Hides the panel from view if there are no panel items in it
+     * @return TabbedPanelBuilder
+     */
+    public TabbedPanelBuilder hideIfEmpty() {
+        this.hideIfEmpty = true;
+        return this;
+    }
     /**
      * Build the panel
      * @return Panel
@@ -126,6 +135,13 @@ public class TabbedPanelBuilder {
         return user;
     }
 
+    /**
+     * @return the hideIfEmpty
+     */
+    public boolean isHideIfEmpty() {
+        return hideIfEmpty;
+    }
+
 
 
 }

src/test/java/world/bentobox/bentobox/api/panels/PanelTest.java

@@ -1,6 +1,3 @@
-/**
- *
- */
 package world.bentobox.bentobox.api.panels;
 
 import static org.junit.Assert.assertEquals;