TreeTraversal.java

class Node
{
    int key;
    Node left, right;

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

class TreeTraversal
{
    Node root;

    TreeTraversal()
    {
        root = null;
    }
    
    void printPostorder(Node node)
    {
        if (node == null)
            return;

        printPostorder(node.left);

        printPostorder(node.right);

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

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

        printInorder(node.left);

        System.out.print(node.key + " ");

        printInorder(node.right);
    }

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

        System.out.print(node.key + " ");

        printPreorder(node.left);

        printPreorder(node.right);
    }

    void printPostorder()  {     printPostorder(root);  }
    void printInorder()    {     printInorder(root);   }
    void printPreorder()   {     printPreorder(root);  }

    public static void main(String[] args)
    {
        BinaryTree tree = new BinaryTree();
        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);

        System.out.println("Preorder Traversal of Binary Tree is ");
        tree.printPreorder();

        System.out.println("\nInorder Traversal of Binary Tree is ");
        tree.printInorder();

        System.out.println("\nPostorder Traversal of Binary Tree is ");
        tree.printPostorder();
    }
}