树结构及前中后续遍历

public class Tree {
    public static void main(String[] args) {
        Tree root = new Tree(50);
        Tree.insert(root, 30);
        Tree.insert(root, 60);
        Tree.insert(root, 70);
        Tree.insert(root, 100);
        Tree.insert(root, 80);
        Tree.VLR(root);
        System.out.println();
        Tree.LDR(root);
        System.out.println();
        Tree.LRD(root);
    }
    
    
    /**数元素*/
    int item;
    /**左节点*/
    Tree left;
    /**右节点*/
    Tree right;

    /**构造函数*/
    public Tree(int e) {
        this.item = e;
        this.left = null;
        this.right = null;
    }

    /**获取元素*/
    public int getItem() {
        return item;
    }

    /**插入元素*/
    public static void insert(Tree root, int value) {
        if(root.item < value) {
            if (root.right == null) {
                root.right = new Tree(value);
            } else {
                insert(root.right, value);
            }
        } else {
            if (root.left == null) {
                root.left = new Tree(value);
            } else {
                insert(root.left, value);
            }
        }
    }

    /**前序排序-VLR*/
    public static void VLR(Tree root) {
        print(root);
        if (root.left != null) {
            VLR(root.left);
        }
        if (root.right != null) {
            VLR(root.right);
        }
    }
   /**中序排序-LDR*/
   public static void LDR(Tree root) {
       if (root.left != null) {
           LDR(root.left);
       }
       print(root);
       if (root.right != null) {
           LDR(root.right);
       }
   }

   /**后序排序-LRD*/
   public static void LRD(Tree root) {
       if (root.left != null) {
           LRD(root.left);
       }
       if (root.right != null) {
           LRD(root.right);
       }
       print(root);
   }

    /**打印*/
    private static void print(Tree root) {
        System.out.print(root.getItem() + " ");
    }

}