Added code for preorder traversal of Tree

Preorder_Tree_Traversal.java

@@ -0,0 +1,39 @@
+class Node {
+    int key;
+    Node left, right;
+
+    public Node(int item)
+    {
+        key = item;
+        left = right = null;
+    }
+}
+
+class BinaryTree {
+    Node root;
+    BinaryTree() { root = null; }
+    void printPreorder(Node node)
+    {
+        if (node == null)
+            return;
+
+        // traverse the root node
+        System.out.print(node.key + " ");
+        // traverse the left child
+        printPreorder(node.left);
+        // traverse the right child
+        printPreorder(node.right);
+    }
+    public static void main(String[] args)
+    {
+        BinaryTree tree = new BinaryTree();
+        tree.root = new Node(1);
+        tree.root.left = new Node(12);
+        tree.root.right = new Node(9);
+        tree.root.left.left = new Node(5);
+        tree.root.left.right = new Node(6);
+
+        System.out.println("\nPreorder traversal of binary tree is ");
+        tree.printPreorder(tree.root);
+    }
+}