@override方法不会覆盖或实现Netbeans中的超类型错误

Question

我试图覆盖程序的方法，当我在addlass的子类中添加@override注释时，它给了我“方法不会覆盖或实现方法”错误。

以下是相关课程

BinarySearchTree.java（超类型）

package dendrology;
import java.util.*;
/**
 *
 * @author X
 */
public class BinarySearchTree<E extends Comparable<E>> implements Iterable<E> {
    BinaryNode<E> myTree;
    public BinarySearchTree() {

    }

    public void add(E toInsert) {
        BinaryNode<E> ptr;
        if (myTree==null) {
            myTree=new BinaryNode<E>(toInsert);
        }
        else {
            ptr=myTree;
            while (true) {
                if (toInsert.compareTo(ptr.info)>0) { //Right branch
                    if (ptr.right==null) { //Stick it here
                        ptr.right=new BinaryNode<E>(toInsert);
                        break;
                    }
                    else ptr=ptr.right;
                }
                else { //Left branch
                    if (ptr.left==null) { //Stick it here
                        ptr.left=new BinaryNode<E>(toInsert);
                        break;
                    }
                    else ptr=ptr.left;
                }
            }
        }
    }

    //Recursive method (from the book)
    BinaryNode<E> findMin(BinaryNode<E> node) {
        if (node==null) return null;
        else if (node.left==null) return node;
        return findMin(node.left);
    }

    //Iterative method (from the book)
    BinaryNode<E> findMax(BinaryNode<E> node) {
        if (node!=null) while (node.right!=null) node=node.right;
        return node;
    }

    //From the book
    BinaryNode<E> remove(E val, BinaryNode<E> tree) {
        int direction; //Used for telling left/right (less-than/greater-than)
        if (tree==null) { //Value to be removed is not present
            return null;
        }
        direction=val.compareTo(tree.info);
        if (direction<0) { //Left branch
            tree.left=remove(val,tree.left);
        }
        else if (direction>0) { //Right branch
            tree.right=remove(val,tree.right);
        }
        else if (tree.left!=null && tree.right!=null) { //Matches current node; two children
            tree.info=findMin(tree.right).info;
            tree.right=remove(tree.info,tree.right);
        }
        else
            tree=(tree.left!=null)?tree.left:tree.right;
        return tree;
    }

    public void remove(E val) {
        BinaryNode<E> discardable=remove(val,myTree);
        System.out.println(":"+discardable.info+":");
    }

    public BinaryNode<E> getRoot() {
        return myTree;
    }

    public Iterator<E> iterator() {
        return new BinaryTreeIteratorBFS<E>(myTree);
    }


}

AVLTree.java（亚型）

package dendrology;

/**
 *
 * @author X
 * @param <E>
 */
public class AVLTree<E> extends BinarySearchTree{

    private int height;

    public AVLTree(){


    }

    @Override
    public void add(E toInsert){
        toInsert=null;
    }

    public preOrder(){


    }

    public inOrder(){


    }    

}