Java写的一个二叉树三种遍历递归算法(仅用作理解三种遍历)

package Binary_Tree_Three_Traversal;
/**
 * 二叉树三种递归遍历
 * @author 1
 *
 */
public class Node {
    public Node left; // 左子结点
    public Node right; // 右子结点
    public int value; // 结点值

    public Node(int value) {
        this.value = value;
    }

    public Node() {
    }
    
    // 前序遍历
    public static void preTraversal(Node node) {
        if (node != null) {
            System.out.print(node.value+" "); //输出当前结点值
        }
        if (node.left != null) {
            preTraversal(node.left); //读左结点
        }
        if (node.right != null) {
            preTraversal(node.right); // 读右结点
        }
    }
    
    // 中序遍历
    public static void midTraversal(Node node){
        if(node.left != null){
            midTraversal(node.left);
        }
        if(node != null){
            System.out.print(node.value+" ");
        }
        if(node.right != null){
            midTraversal(node.right);
        }
    }
    
    // 后序遍历
    public static void behTraversal(Node node){
        if(node.left != null){
            behTraversal(node.left);
        }
        if(node != null){
            System.out.print(node.value+" ");
        }
        if(node.right != null){
            behTraversal(node.right);
        }
    }
    public static void main(String[] args) {
        // 初始化5个结点,值分别为: 1,2,3,4,5
        Node n1 = new Node(1);
        Node n2 = new Node(2);
        Node n3 = new Node(3);
        Node n4 = new Node(4);
        Node n5 = new Node(5);
        Node n6 = new Node(); // 值默认为0
        Node n7 = null;
        
        System.out.println("n6 = "+n6); 
        System.out.println("n7 = "+n7); // null
        
        // 构建二叉树, 以n1为根结点
        n1.left = n2;
        n1.right = n5;
        n2.left = n3;
        n2.right = n4;
        n5.left = n6;
        n5.right = n7;
        
        System.out.print("前序遍历结果为: ");
        preTraversal(n1); 
        System.out.println();
        System.out.print("中序遍历结果为: ");
        midTraversal(n1);
        System.out.println();
        System.out.print("后序遍历结果为: ");
        behTraversal(n1);
    }
}