Add methods for traversing trees

app/src/main/java/ch/nuth/zhaw/exbox/SortedBinaryTree.java

@@ -68,8 +68,7 @@ public class SortedBinaryTree<T extends Comparable<T>> implements Tree<T> {
     }
 
     public Traversal<T> traversal() {
-        // TODO Implement
-        return null;
+        return new TreeTraversal<>(root);
     }
 
     protected int calcHeight(TreeNode<T> node) {

app/src/main/java/ch/nuth/zhaw/exbox/TreeTraversal.java

@@ -1,5 +1,8 @@
 package ch.nuth.zhaw.exbox;
 
+import java.util.Deque;
+import java.util.LinkedList;
+
 public class TreeTraversal<T extends Comparable<T>> implements Traversal<T> {
     private final TreeNode<T> root;
 
@@ -8,21 +11,59 @@ public class TreeTraversal<T extends Comparable<T>> implements Traversal<T> {
     }
 
     public void inorder(Visitor<T> vis) {
-        // TODO Implement
+        if (root.left != null) {
+            new TreeTraversal<>(root.left).inorder(vis);
+        }
+
+        vis.visit(root.getValue());
+
+        if (root.right != null) {
+            new TreeTraversal<>(root.right).inorder(vis);
+        }
     }
 
     public void preorder(Visitor<T> vis) {
-        // TODO Implement
+        vis.visit(root.getValue());
+
+        if (root.left != null) {
+            new TreeTraversal<>(root.left).preorder(vis);
+        }
+
+        if (root.right != null) {
+            new TreeTraversal<>(root.right).preorder(vis);
+        }
     }
 
     public void postorder(Visitor<T> vis) {
-        // TODO Implement
+        if (root.left != null) {
+            new TreeTraversal<>(root.left).postorder(vis);
+        }
+
+        if (root.right != null) {
+            new TreeTraversal<>(root.right).postorder(vis);
+        }
+
+        vis.visit(root.getValue());
     }
 
     @Override
     public void levelorder(Visitor<T> vistor) {
-        // TODO Auto-generated method stub
-        
+        Deque<TreeNode<T>> queue = new LinkedList<>();
+        queue.add(root);
+
+        while (!queue.isEmpty()) {
+            TreeNode<T> node = queue.poll();
+
+            if (node.left != null) {
+                queue.add(node.left);
+            }
+
+            if (node.right != null) {
+                queue.add(node.right);
+            }
+
+            vistor.visit(node.getValue());
+        }
     }
 
     @Override