Here is a simple and short Java program to find the sum of all nodes in a binary tree using recursion:

• ✅ Java Code: Sum of All Nodes (Minimal Version)

class Node {

int data;

Node left, right;

Node(int data) {

this.data = data;

}

}

public class SumOfNodes {

int sum(Node node) {

if (node == null) return 0;

return node.data + sum(node.left) + sum(node.right);

}

public static void main(String[] args) {

Node root = new Node(10);

root.left = new Node(5);

root.right = new Node(15);

root.left.left = new Node(2);

root.right.right = new Node(8);

SumOfNodes tree = new SumOfNodes();

System.out.println(“Sum of all nodes: ” + tree.sum(root));

}

}

📌 Output:

Sum of all nodes: 40

💡 Explanation:

Recursively add node.data with sum of left and right subtrees.

If node is null, return 0.