TreeHeight.java

public class TreeHeight {

    static class Node {
        char data;
        Node left, right;

        Node(char data) {
            this.data = data;
        }

        Node(char data, Node left, Node right) {
            this.data = data;
            this.left = left;
            this.right = right;
        }

        @Override
        public String toString() {
            return String.valueOf(data);
        }
    }

    public static void main(String[] args) {

        Node f = new Node('f');
        Node g = new Node('g');
        Node h = new Node('h');


        Node d = new Node('d', f, g);
        Node e = new Node('e', null, h);

        Node c = new Node('c', d, e);
        Node b = new Node('b');

        Node a = new Node('a', b, c);

        System.out.println(nodeHeight(a));

    }

    static int nodeHeight(Node root) {
        if (root == null) {
            return 0;
        } else {
            int leftHeight = nodeHeight(root.left);
            int rightHeight = nodeHeight(root.right);
            return 1 + (leftHeight > rightHeight ? leftHeight : rightHeight);
        }
    }
}