JAVA二叉树的几种遍历(递归，非递归)实现

//创建一个节点类
 class Node {
  public int key;//节点的值
  public String Data;//节点存储的内容
  public Node leftNode;//左孩子
  public Node rightNode;//右孩子

  //节点类的构造方法
  public Node(int key,String Data){
    this.key=key;
    this.Data=Data;
    this.leftNode=null;
    this.rightNode=null;
  }

  //得到数据
  public int getKey(){
    return key;

}

}
public class BinaryTree {
  public Node root;
  public int h=0;

  //插入数据
  public void insert(int key,String Data){
    //实例化一个节点
    Node newNode=new Node(key, Data);
    //判断此二叉树是否有根节点
    if(root==null){
      root=newNode;

    }
    else
    {
      Node current=root;
      Node parent;
      while(true){
        parent=current;
        //判断大小，决定新节点是放在左边还是右边
        if(key<current.key){
          current=current.leftNode;//往左子树方向找
          if(current==null){
            parent.leftNode=newNode;//找到叶子节点
            return;
          }//叶子节点的If end;
        }//左子树的If end;
        else{
          current=current.rightNode;
          if(current==null){
            parent.rightNode=newNode;
            return;
          }//叶子
        }//右子树

      }
    }
  }//insert end;

//打印
  public void printlTree(Node node){
    System.out.print("*");

    System.out.print(node.getKey());


  }




  //深度
  public int Height(Node node){
    if(node==null){
      return 0;
    }
    else{
      int i=Height(node.leftNode);
      int j=Height(node.rightNode);
      return (i>j)?(i+1):(j+1);

    }
  }

  //节点个数
  public int NodeNum(Node node){
    if(node==null){
      return 0;
    }
    return NodeNum(node.leftNode)+NodeNum(node.rightNode)+1;

  }

  //第K层节点的个数
  public int getLeafNodeNum(Node node,int i){
    if(node==null){
      return 0;
    }
    else{
      if(i==0){
        return 1;
      }
      else{
        int numLeft=getLeafNodeNum(node.leftNode,i-1);
        int numRight=getLeafNodeNum(node.rightNode,i-1);
        return (numLeft+numRight);
      }
    }
    }



  //分层遍历
  public void LevelOrder(Node node){
    Queue<Node> queue=new LinkedList<Node>();
    if(node==null){
      return;
    }
    queue.add(node);
    while(!queue.isEmpty()){
      Node temp=queue.poll();
      System.out.print("*");
      System.out.print(temp.getKey());
      if(temp.leftNode!=null){
        queue.add(temp.leftNode);
      }
      if(temp.rightNode!=null){
        queue.add(temp.rightNode);
      }
    }
  }

  //递归前序遍历
  public void preOrder(Node node){
    if(node!=null){
    printlTree(node);
    preOrder(node.leftNode);
    preOrder(node.rightNode);
  }
  }
  //非递归前序遍历
  public void NpreOrder(Node node){

    Stack<Node> sk=new Stack<Node>();
    Node n=node;
    while(!sk.isEmpty()||n!=null){
      if(n!=null){
      System.out.print("<<<");
      System.out.print(n.getKey());

      sk.push(n);
      n=n.leftNode;
      }

      else{
      n=sk.pop();;
      n=n.rightNode;
    }
  }
  }


  //中序遍历
    public void inOrder(Node node){
      if(node!=null){
      preOrder(node.leftNode);
      printlTree(node);

      preOrder(node.rightNode);
    }
    }

    //非递归的中序遍历
    public void NinOrder(Node node){
      Stack<Node> s=new Stack<Node>();
      Node n=node;
      while(n!=null||!s.isEmpty()){
        if(n!=null){
          s.push(n);
          n=n.leftNode;
        }
        else{
          n=s.pop();
          System.out.println(n.getKey());
          n=n.rightNode;

        }
      }
    }

    //后序遍历
        public void postOrder(Node node){
          if(node!=null){
          preOrder(node.leftNode);

          preOrder(node.rightNode);
          printlTree(node);

        }
        }

        //非递归后序遍历
        public void NpostOrder(Node node){
          Stack<Node> s1=new Stack<Node>();//第一次入栈
          Stack<Node> s2=new Stack<Node>();//第二次入栈
          Node n=node;
        while(!s1.isEmpty()||n!=null){
          if(n!=null){
            s1.push(n);
            s2.push(n);
            n=n.rightNode;
          }
          else{
            n=s1.pop();
            n=n.leftNode;
          }
        }
        while(!s2.isEmpty()){
          System.out.println("((("+s2.pop().getKey());
        }

        }

public static void main(String[] args) {

    BinaryTree bt=new BinaryTree();
    bt.insert(12, "A");
    bt.insert(10, "B");
    bt.insert(15, "C");
    bt.insert(9, "D");
    bt.insert(11, "E");
    bt.insert(14, "F");
    bt.insert(16, "G");

   System.out.println("这个二叉树的深度："+bt.Height(bt.root));
    System.out.println("这个二叉树的节点个数："+bt.NodeNum(bt.root));


    System.out.println("前序遍历：");
    bt.preOrder(bt.root);
    System.out.println();

    System.out.println("非递归前序遍历：");
    bt.NpreOrder(bt.root);
    System.out.println();

    System.out.println("中序遍历：");
    bt.inOrder(bt.root);
    System.out.println();

    System.out.println("非递归中序遍历：");
    bt.NinOrder(bt.root);
    System.out.println();

    System.out.println("后序遍历：");
    bt.postOrder(bt.root);
    System.out.println();

    System.out.println("非递归后序遍历：");
    bt.NpostOrder(bt.root);
    System.out.println();

    System.out.println("分层遍历：");
    bt.LevelOrder(bt.root);
    System.out.println();

    System.out.println("第二层有"+bt.getLeafNodeNum(bt.root, 2));

  }
    }