Coding along

src/Traversal.java

@@ -1,5 +1,79 @@
 public class Traversal {
   public static void main(String[] args) {
+    TreeNode root = new TreeNode(10);
+
+    // Root left & right
+    root.left = new TreeNode(9);
+    root.right = new TreeNode(15);
 
+    // Child of 10's first child
+    root.left.left = new TreeNode(5);
+    root.left.right = new TreeNode(2);
+
+    // Child of 10's second child
+    root.right.left = new TreeNode(-3);
+    root.right.right = new TreeNode(5);
+
+    root.right.right.right = new TreeNode(22);
+
+    System.out.println("Pre-order: ");
+    preOrder(root);
+    System.out.println();
+
+    System.out.println("Post-order: ");
+    postOrder(root);
+    System.out.println();
+
+    System.out.println("In-order: ");
+    inOrder(root);
+    System.out.println();
+
+  }
+
+ /** PRE - ORDER
+    if null : return
+    print data
+    search left
+    search right
+    */
+  public static void preOrder(TreeNode current){
+
+    if (current == null) return;
+    System.out.println(current.data);
+    preOrder(current.left);
+    preOrder(current.right);
+
+  }
+
+
+  /** POST - ORDER
+   if null : return
+   search left
+   search right
+   print data
+   */
+  public static void postOrder(TreeNode current){
+
+    if (current == null) return;
+    preOrder(current.left);
+    preOrder(current.right);
+    System.out.println(current.data);
   }
+
+
+   /** IN - ORDER
+   if null : return
+   search left
+   print data
+   search right
+   */
+  public static void inOrder(TreeNode current){
+
+    if (current == null) return;
+    preOrder(current.left);
+    System.out.println(current.data);
+    preOrder(current.right);
+
+  }
+
 }

src/TreeNode.java

@@ -1,4 +1,9 @@
 public class TreeNode {
+    public int data;
+    public TreeNode left;
+    public TreeNode right;
 
-
+    public TreeNode(int data){
+        this.data = data;
+    }
 }