Set in order successor of a node in java http://www.geeksforgeeks.org/inorder-successor-in-binary-search-tree/

NodeSuccessor.java

public class NodeSuccessor {

	// Node class;; ignoring getters and setters for simplicity
	private static class Node {
		public Node(int value) {
			this.value = value;
		}

		Node successor;
		Node left;
		Node right;
		int value;
	}

	// Holds the last traversed node;; ignoring getters and setters for
	// simplicity
	private static class NodeHolder {
		Node traversedNode;
	}

	public static void main(String[] args) {
		Node node20 = new Node(20);
		Node node30 = new Node(30);
		Node node40 = new Node(40);
		Node node50 = new Node(50);
		Node node60 = new Node(60);
		Node node90 = new Node(90);
		Node node100 = new Node(100);
		node20.left = node30;
		node20.right = node40;
		node30.left = node50;
		node30.right = node60;
		node60.left = node90;
		node60.right = node100;
		inOrderTraversal(node20);
		setSucc(node20, new NodeHolder());
		inOrderTraversal(node20);
	}

	public static void setSucc(Node node, NodeHolder nodeHolder) {
		if (null == node) {// corner case for NULL Tree
			return;
		}
		if (node.right != null) {
			setSucc(node.right, nodeHolder);
		}
		node.successor = nodeHolder.traversedNode;
		nodeHolder.traversedNode = node;
		if (node.left != null) {
			setSucc(node.left, nodeHolder);
		}
	}

	public static void inOrderTraversal(Node node) {
		if (null == node) {// corner case for NULL Tree
			return;
		}
		if (node.left != null) {
			inOrderTraversal(node.left);
		}
		System.out.println("Node :" + node.value + ", " + "Successor "
				+ (node.successor == null ? null : node.successor.value));
		if (node.right != null) {
			inOrderTraversal(node.right);
		}
	}

}