Solution Optionals 03

Author: SteffenLm

Crate.java

@@ -1,3 +1,5 @@
+import java.util.Optional;
+
 public class Crate<T> {
 
   private T box1;
@@ -22,18 +24,20 @@ public void insertBottle(T bottle, int box) throws CrateIndexOutOfBoundsExceptio
     }
   }
 
-  public T takeBottle(int box) throws CrateIndexOutOfBoundsException {
+  public Optional<T> takeBottle(int box) throws CrateIndexOutOfBoundsException {
     if (box < 1 || box > 6) {
       throw new CrateIndexOutOfBoundsException();
     }
 
-    return switch (box) {
+    T foundBox = switch (box) {
       case 1 -> box1;
       case 2 -> box2;
       case 3 -> box3;
       case 4 -> box4;
       case 5 -> box5;
-      default -> box6;
+      case 6 -> box6;
+      default -> null;
     };
+    return Optional.ofNullable(foundBox);
   }
 }

Exercise.java

@@ -11,9 +11,14 @@ public static void main(String[] args) {
       crate.insertBottle(new WineBottle(), 5);
       crate.insertBottle(new WineBottle(), 6);
 
-      if (crate.takeBottle(3) instanceof BeerBottle beerBottle) {
-        beerBottle.chugALug();
-      }
+      crate.takeBottle(3)
+          .ifPresentOrElse(
+              bottle -> {
+                if (bottle instanceof BeerBottle beerBottle) {
+                  beerBottle.chugALug();
+                }
+              },
+              () -> System.out.println("Gesuchte Flasche ist nicht vorhanden."));
     } catch (CrateIndexOutOfBoundsException e) {
       System.err.println(e.getMessage());
     }