/**
     * 前序遍历
     * @param tree
     */
    public void preOrder(BSTree tree){
        preOrder(tree.mRoot);
    }
     preOrder(BSTNode node){
        if(node!=null){
            System.out.print(node.key+"");
            preOrder(node.left);
            preOrder(node.right);
        }
    }
    
     * 中序遍历
     *  midOrder(BSTree tree){
        midOrder(tree.mRoot);
    }
     midOrder(BSTNode node){
        ){
            midOrder(node.left);
            System.out.print(node.key+"");
            midOrder(node.right);
        }
    }
    
     * 后序遍历
     *  postOrder(BSTree tree){
        postOrder(tree.mRoot);
    }
     postOrder(BSTNode node){
        ){
            postOrder(node.left);
            postOrder(node.right);
            System.out.print(node.key+"");
        }
    }
    
     * 二叉树的查找
     *  tree
     *  key
     * @return
     public BSTNode<T> search(BSTree<T> tree,T key){
        BSTNode<T> mRoot=tree.mRoot;
        while(mRoot!=){
            int flag=key.compareTo(mRoot.key);
            if(flag<0){
                mRoot=mRoot.left;
            }else if(flag>0mRoot.right;
            }else{
                return mRoot;
            }
        }
         mRoot;
    }

        tree.preOrder(tree);//输出 312546
        tree.midOrder(tree);输出 123456
        tree.postOrder(tree);输出 214653
        BSTree.BSTNode node=tree.search(tree,5);
        System.out.println(node.left.key);输出 4