Refactor switch statements and simplify typecasting.

Refactored multiple switch statements to use the enhanced switch syntax for better readability and simplicity. Simplified typecasting by combining the instanceof check and cast into a single statement.

src/main/java/org/gestern/gringotts/Util.java

@@ -168,11 +168,10 @@ public static Block chestBlock(Sign sign) {
         Block signBlock = sign.getBlock();
         BlockData blockData = signBlock.getBlockData();
 
-        if (!(blockData instanceof WallSign)) {
+        if (!(blockData instanceof WallSign signData)) {
             return null;
         }
 
-        WallSign signData = (WallSign) blockData;
         BlockFace attached = signData.getFacing().getOppositeFace();
 
         // allow either the block sign is attached to or the block below the sign as
@@ -197,18 +196,10 @@ public static boolean isValidContainer(Material material) {
             return false;
         }
 
-        switch (material) {
-            case CHEST:
-            case TRAPPED_CHEST:
-            case DISPENSER:
-            case FURNACE:
-            case HOPPER:
-            case DROPPER:
-            case BARREL:
-                return true;
-            default:
-                return false;
-        }
+        return switch (material) {
+            case CHEST, TRAPPED_CHEST, DISPENSER, FURNACE, HOPPER, DROPPER, BARREL -> true;
+            default -> false;
+        };
     }
 
     /**
@@ -218,18 +209,10 @@ public static boolean isValidContainer(Material material) {
      * @return whether the given inventory type is valid for Gringotts
      */
     public static boolean isValidInventory(InventoryType inventory) {
-
-        switch (inventory) {
-            case CHEST:
-            case DISPENSER:
-            case FURNACE:
-            case HOPPER:
-            case DROPPER:
-            case BARREL:
-                return true;
-            default:
-                return false;
-        }
+        return switch (inventory) {
+            case CHEST, DISPENSER, FURNACE, HOPPER, DROPPER, BARREL -> true;
+            default -> false;
+        };
     }
 
     /**