solved Task 4

src/ch/zhaw/ads/AVLSearchTree.java

@@ -12,9 +12,10 @@ public class AVLSearchTree<T extends Comparable<T>> extends SortedBinaryTree<T>
         || (node.right != null && !balanced(node.right))
         || (node.left != null && !balanced(node.left))){
             return false;
-        }
+        } else {
             return true;
         }
+    }
 
     public boolean balanced() {
         return balanced(root);