Boundary traversal or printing border nodes of a binary tree.

/*
 Tree :
50
30    70
 20  40  60  80
        35  45
   

 Boundary Traversal : 50 30 20 35 45 60 80 70

 Logic:
 1. Print Root Node.
 2. Print Leftmost Branch except Leaf Node.
 3. Print all leaf nodes.
 4. Print Rightmost branch except Leaf Node.
*/

 public void boundaryTraversal()
 {
printRootNode();
printLeftBranch(root.getLeftChild());
printLeafNodes(root);
printRightBranch(root.getRightChild());
 }

 public void printRootNode()
 {
System.out.println(root.getData());
 }

 public void printLeftBranch(BSTNode n)
 {
if(n.getLeftChild() != null)
{
System.out.println(n.getData());
printLeftBranch(n.getLeftChild());
}
 }

 public void printLeafNodes(BSTNode n)
 {
if(n.getRightChild() ==null && n.getLeftChild() == null)
{
System.out.println(n.getData());
return;
}
printLeafNodes(n.getLeftChild());
printLeafNodes(n.getRightChild());
 }

 public void printRightBranch(BSTNode n)
 {
if(n.getRightChild() != null)
{
System.out.println(n.getData());
printRightBranch(n.getRightChild());
}
 }