Binary Trees1-Nodes without sibling

For a given Binary Tree of type integer, print all the nodes without any siblings.
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 node data in a top to down fashion with reference to the root. 
Node data in the left subtree will be printed first and then the right subtree.
A single space will separate them all.
 Constraints:
1 <= N <= 10^5
Where N is the total number of nodes in the binary tree.

Time Limit: 1 second
Sample Input 1:
5 6 10 2 3 -1 -1 -1 -1 -1 9 -1 -1
Sample Output 1:
9    
Sample Input 2:
2 4 5 6 -1 -1 7 20 30 80 90 -1 -1 -1 -1 -1 -1 -1 -1
Sample Output 2:
6 7  
Explanation of Sample Input 2:
The input tree when represented in a two-dimensional plane, it would look like this:     
alt txt

In respect to the root, node data in the left subtree that satisfy the condition of not having a sibling would be 6, taken in a top-down sequence. Similarly, for the right subtree, 7 is the node data without any sibling.

Since we print the siblings in the left-subtree first and then the siblings from the right subtree, taken in a top-down fashion, we print 6 7.

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

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