Binary Trees1-Postorder Binary Tree

For a given Binary Tree of integers, print the post-order traversal.
Input Format:
The first and the only line of input will contain the node data, all separated by a single space. Since -1 is used as an indication whether the left or right node data exist for root, it will not be a part of the node data.
Output Format:
The only line of output prints the post-order traversal of the given binary tree.
Constraints:
1 <= N <= 10^6
Where N is the total number of nodes in the binary tree.

Time Limit: 1 sec
Sample Input 1:
1 2 3 4 5 6 7 -1 -1 -1 -1 -1 -1 -1 -1
 Sample Output 1:
4 5 2 6 7 3 1 
Sample Input 2:
5 6 10 2 3 -1 -1 -1 -1 -1 9 -1 -1
 Sample Output 1:
2 9 3 6 10 5 

**************************************Code*************************************

public static void postOrder(BinaryTreeNode<Integer> root) {
		
		if(root==null)
			return;
		postOrder(root.left);
		postOrder(root.right);
		System.out.print(root.data+" ");
	}