Error with two different generic types

Question

So, I understand this error message is telling me what is wrong, but I am having trouble determining why I am coming up with this error and how to resolve it:

constructor Node in class Node cannot be applied to given types required: E#1 found: no arguments reason: actual and formal argument lists differ in length where E#1,E#2 are type-variables: E#1 extends Object declared in class MyStack E#2 extends Object declared in class Node

I have implemented stacks in the past with linked lists and never ran into this before. I have included the first sections of code for my MyStack class and Node class, as I don't believe the methods contained are relevant. If they are I'm happy to edit them in. My main issue is I don't understand why it is making two separate generic types. I understand it is telling me that actual and formal argument lists differ in length, but how can that be and what could I do to resolve this?

public class MyStack<E> extends Node<E>{

//pieced together linked list
private int cnt;
private Node<E> head;


public MyStack() {
    head = null;
    cnt = 0;
}

Here is the Node Class.

public class Node <E>{ 



public Node<E> link;
public E item;

public Node(E data) {
    item = data;
    link = null;
}

Any clues as to why this is showing 2 different generic types would be helpful. Cheers!

Answer 1

As there is no no-argument constructor for Node , and MyStack extends Node , you'll need to specify how the constructor for MyStack is going to call the constructor for Node . Currently, this won't compile because you don't have the super constructor call at the start of the constructor for MyStack .