Tree Traversal : Inorder Preorder Postorder in Java

// Node class represents each node in the binary tree
class Node {
    int key;
    Node left, right;

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

// BinaryTree class contains traversal methods
class BinaryTree {

    Node root;

    BinaryTree() {
        root = null;
    }

    // Preorder Traversal (Root → Left → Right)
    void preorder(Node node) {

        if (node == null)
            return;

        System.out.print(node.key + " ");
        preorder(node.left);
        preorder(node.right);
    }

    // Inorder Traversal (Left → Root → Right)
    void inorder(Node node) {

        if (node == null)
            return;

        inorder(node.left);
        System.out.print(node.key + " ");
        inorder(node.right);
    }

    // Postorder Traversal (Left → Right → Root)
    void postorder(Node node) {

        if (node == null)
            return;

        postorder(node.left);
        postorder(node.right);
        System.out.print(node.key + " ");
    }
}

public class Main {

    public static void main(String[] args) {

        BinaryTree tree = new BinaryTree();

        // Creating the binary tree
        tree.root = new Node(1);
        tree.root.left = new Node(2);
        tree.root.right = new Node(3);
        tree.root.left.left = new Node(4);
        tree.root.left.right = new Node(5);

        // Traversals
        System.out.print("Preorder Traversal: ");
        tree.preorder(tree.root);

        System.out.print("\nInorder Traversal: ");
        tree.inorder(tree.root);

        System.out.print("\nPostorder Traversal: ");
        tree.postorder(tree.root);
    }
}