节点类

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

测试实例

import java.util.Stack;

//树的遍历
public class Tree {

    //递归先序遍历
    public static void preOrderRecur(Node  head){
        if(head==null){
            return;
        }
        System.out.print(head.value+"   ");
        preOrderRecur(head.left);
        preOrderRecur(head.right);
    }
    //递归中序遍历
    public static void inOrderRecur(Node  head){
        if(head==null){
            return;
        }
        inOrderRecur(head.left);
        System.out.print(head.value+"   ");
        inOrderRecur(head.right);
    }
    //非递归实现后序遍历（两个栈）
    public static void posOrderUnrecur(Node head){
        if(head!=null){
            Stack<Node> s1=new Stack<Node>();
            Stack<Node> s2=new Stack<Node>();
            s1.push(head);
            while(!s1.isEmpty()){
                head=s1.pop();
                s2.push(head);
                if(head.left!=null){
                    s1.push(head.left);
                }
                if(head.right!=null){
                    s1.push(head.right);
                }
            }
            while(!s2.isEmpty()){
                System.out.print(s2.pop().value+"   ");
            }
        }
        System.out.println();
    }

    
    public static void main(String[] args) {
        Tree tree = new Tree();
        Node node1=new Node(1);
        Node node2=new Node(2);
        Node node3=new Node(3);
        Node node4=new Node(4);
        Node node5=new Node(5);
        Node node6=new Node(6);
        Node node7=new Node(7);
        node1.left=node2;
        node1.right=node3;
        node2.left=node4;
        node2.right=node5;
        node3.left=node6;
        node3.right=node7;
        preOrderRecur(node1);
        System.out.println();
        inOrderRecur(node1);
        System.out.println();
        posOrderUnrecur(node1);
    }

}