在二叉树中找到一个节点的后继节点

public class Node {
public int value;
public Node left;
public Node right; 
public Node parent;
public Node(int data) { 
    this.value = data; 
    }
} 

class PNode {
     public int value;
     public PNode left;
     public PNode right;
     public PNode parent;
     public PNode(int data) {
         this.value = data;
     }
 }

 public static PNode getSuccessorNode(PNode node){
     if (node == null) return node;
     if (node.right != null) return mostLeftNode(node.right);
     else {
         PNode parent = node.parent;
         while (parent != null && parent.left != node){
             node = parent;
             parent = node.parent;
         }
         return parent;
     } 
 }

 public static PNode mostLeftNode(PNode node){
     if (node == null) return node;
     while (node.left != null){
         node = node.left;
     }
     return node;
 }