二叉樹的下一個節點（Java）

package 劍指offer;

public class Inteview8 {

	/**
	 * 題目：給定一科二叉樹和其中一個節點，
	 * 如何找出中序遍歷序列的下一個節點？
	 * 書中的節點除了有兩個分別指向左右節點的指針，
	 * 還有一個指向父節點的指針
	 * @param args
	 */
	public class BinaryTreeNode{
		int val;
		BinaryTreeNode left;
		BinaryTreeNode right;
		BinaryTreeNode parent;
		public BinaryTreeNode(int val){
			this.val=val;
			this.left=left;
			this.right=right;
			this.parent=parent;
		}
	}

	public static BinaryTreeNode nextNode(BinaryTreeNode node){
		BinaryTreeNode nextnode = null;
		if(node==null)return null;
		//如果該節點的右子樹不爲空
		if(node.right!=null){
			nextnode=node.right;
			while(nextnode.left!=null){
				nextnode=nextnode.left;
			}
		}
		//如果該節點的右子樹爲空
		if(node.right==null){
			if(node.parent!=null){
				//如果該節點是父節點的左子樹
				if(node.parent.left==node){
					System.out.println("該節點是父節點的左子樹");
					nextnode=node.parent;
				}
			    //如果該節點是父節點的右子樹
				else if(node.parent.right==node){
					while(node.parent!=null&&node.parent.right==node){
						System.out.println("該節點是父節點的右子樹"+node.val);
						node=node.parent;
					}
					nextnode=node.parent;
			     }
		   }
		}
		return nextnode;
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Inteview8 in=new Inteview8();
		//創建一棵樹
		/**
		 *                  1
		 *        2                   3
		 *    4       5            6      7
		 *      8        9
		 *                     
		 */
		BinaryTreeNode root=in.new BinaryTreeNode(1);
		BinaryTreeNode node1=in.new BinaryTreeNode(2);
		BinaryTreeNode node2=in.new BinaryTreeNode(3);
		BinaryTreeNode node3=in.new BinaryTreeNode(4);
		BinaryTreeNode node4=in.new BinaryTreeNode(5);
		BinaryTreeNode node5=in.new BinaryTreeNode(6);
		BinaryTreeNode node6=in.new BinaryTreeNode(7);
		BinaryTreeNode node7=in.new BinaryTreeNode(8);
		BinaryTreeNode node8=in.new BinaryTreeNode(9);
		root.left=node1;
		root.right=node2;
		root.parent=null;
		node2.parent=root;
		node1.parent=root;
		node1.left=node3;
		node3.parent=node1;
		node1.right=node4;
		node4.parent=node1;

		node2.left=node5;
		node5.parent=node2;
		node2.right=node6;
		node6.parent=node2;
		node3.right=node7;
		node7.parent=node3;
		
		node4.right=node8;
		node8.parent=node4;
		BinaryTreeNode N1=nextNode(node8);
		System.out.println(N1.val);
		BinaryTreeNode N2=nextNode(node4);
		System.out.println(N2.val);
		BinaryTreeNode N3=nextNode(node7);
		System.out.println(N3.val);
		BinaryTreeNode N4=nextNode(node6);
	//	System.out.println(N4.val);
		
		
		
	}

}