Java Program to Perform the preorder tree traversal

In this example, we will learn to perform the preorder tree traversal in Java.

To understand this example, you should have the knowledge of the following Java programming topics:

Example: Java Program to perform preorder tree traversal

class Node {
  int item;
  Node left, right;

  public Node(int key) {
  item = key;
  left = right = null;
  }
}

class Tree {
  // root of Tree
  Node root;

  Tree() {
  root = null;
  }

  void preorder(Node node) {
    if (node == null)
      return;

    // traverse the root node
    System.out.print(node.item + "->");
    // traverse the left child
    preorder(node.left);
    // traverse the right child
    preorder(node.right);
  }

  public static void main(String[] args) {
    // create object of tree
    Tree tree = new Tree();

    // create nodes of the tree
    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);

    // preorder tree traversal
    System.out.println("\nPreorder traversal ");
    tree.preorder(tree.root);
  }
}