Linked list with inorder successor

Problem

Create a linked list with the nodes of a binary tree in an inorder succession.

Solution

We traversed the tree recursively in inorder traversal. While doing so, we took two other variables, named linker and head. When the first node is visited in an inorder traversal the head node and linker are initialized. Then for next inorder successors, head is never touched but linker is used to link the next elements.

Code

public class InorderSuccessor
{

 public static void main(String[] args)
 {
  NextNode a=new NextNode(1);
  NextNode b=new NextNode(2);
  NextNode c=new NextNode(3);
  NextNode d=new NextNode(4);
  NextNode e=new NextNode(5);
  NextNode f=new NextNode(6);
  NextNode g=new NextNode(7);
  NextNode h=new NextNode(8);
  NextNode i=new NextNode(9);
  a.left=b;
  a.right=c;
  b.right=d;
  c.left=e;
  c.right=f;
  d.left=g;
  d.right=h;
  g.right=i;
  NextNode head=linkInorderSuccessor(a);
  while(head!=null)
  {
   System.out.println(head.value);
   head=head.next;
  }

 }
 
 public static NextNode linkInorderSuccessor(NextNode root)
 {
  NodeContainer linker=new NodeContainer();
  NodeContainer head=new NodeContainer();
  linkInorderSuccessor(root, linker, head);
  return head.node;
 }
 
 private static void linkInorderSuccessor(NextNode root, NodeContainer linker, NodeContainer head)
 {
  if(root==null)
   return;
  linkInorderSuccessor(root.left,linker,head);
  if(head.node==null&&root!=null)
   head.node=root;
  if(linker.node!=null)
   linker.node.next=root;
  linker.node=root;
  linkInorderSuccessor(root.right, linker, head);
 }

}

class NextNode
{
 public NextNode left;
 public NextNode right;
 public NextNode next;
 public int value;
 public NextNode(int value)
 {
  this.value=value;
 }
}

class NodeContainer
{
 public NextNode node;
}