树结构及前中后续遍历

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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() + " ");     }   }