我试着做一个二叉搜索树（bst）来从menuitem类中找到对象，在那里可以找到菜名。但是，出了点问题，我不知道怎么了？
我的目标：
menuitem search（string name）–遍历树并返回对menuitem的引用，其中的搜索键（name）与参数匹配。如果未找到，则返回null。
这是我的bst课程：

public class BST {

    private BSTNode root;

    public BST() {  
        root = null;
    }

    public void insert(MenuItem mi) {
        if (root == null)
            root = new BSTNode(mi, null, null);
        else
            insert(root, mi); 
    }

     private void insert(BSTNode cur, MenuItem mi) {
            if (mi.compareTo(cur.getData()) < 0)
                if (cur.getLeft() != null)
                    insert(cur.getLeft(), mi);
                else
                    cur.setLeft(new BSTNode(mi, null, null));
            else if (mi.compareTo(cur.getData()) > 0)
                if (cur.getRight() != null)
                    insert(cur.getRight(), mi);
                else
                    cur.setRight(new BSTNode(mi, null, null));
            else
                //If item is same then just add quantity in existing node
                cur.getData().setQuantity(cur.getData().getQuantity() + mi.getQuantity()); 
        }

    public void preorder() {
        printPreOrder(root);

    }

    private void printPreOrder(BSTNode root) {
        if(root != null) {
        System.out.print(root.getData());
        printPreOrder(root.getLeft());
        printPreOrder(root.getRight());
        }
    }

    public void postorder() {
        printPost(root);
    }

    private void printPost(BSTNode root) {
        if(root != null) {
            printPost(root.getLeft());
            printPost(root.getRight());
            System.out.println(root.getData());
        }
    }

    public void inorder() {
        printInorder(root);
    }

    private void printInorder(BSTNode root) {
        if(root != null) {
            printInorder(root.getLeft());
            System.out.println(root.getData());
            printInorder(root.getRight());
            }
        }

    public int size(){
        return size(root);
    }

    private int size(BSTNode cur){
        if (cur==null)
            return 0;
        return 1 + size(cur.getLeft()) + size(cur.getRight());
    }

    public int depth(BSTNode root) {
        if (root == null)
            return 0;
        else {

            int leftDepth = depth(root.getLeft()); 
            int rightDepth = depth(root.getRight()); 

            if (leftDepth > rightDepth) 
             return (leftDepth + 1); 
            else 
              return (rightDepth + 1); 
        }
    }

    public MenuItem search(String name) {
        if(root == null)
            return null;
        else
            return search(name,root);   

    }

    private MenuItem search(String name, BSTNode root) {
        if(name == root.getData()) {
            return root;
        }
         if ( name.compareTo(BSTNode.getData()) < 0 ){
                if(BSTNode.getLeft() == null){
                    System.out.println("Item not found.");
                    return null;
                }else{
                    return search(name, BSTNode.getLeft());
                }
            }else{
                if (BSTNode.getRight() == null ){
                    System.out.println("Item not found.");
                    return null;
                }else{
                    return search(name, BSTNode.getRight());
                }
            }

    }

    public double getTotalBeforeTax() {
         return 0;
    }

    public double getTax(double taxrate) {
        return getTotalBeforeTax()*taxrate;

    }

    public double getTip(double tipPercent){
        return getTotalBeforeTax()*tipPercent;
    }

    public String toString() {
        return null;
    }

}