作用域中无法访问类型为OuterClass.StaticNestedClass的封闭实例

Question

I am still learning and currently trying to implement DoublyLinkedLists with nested STATIC classes and getting the error below:

No enclosing instance of the type OuterClass.StaticNestedClass is accessible in scope Actual error:
No enclosing instance of the type SolutionDLL.Node is accessible in scope

I have two STATIC nested classes inside the outer class SolutionDLL class:

class SolutionDLL {
    public static class Node {
        private Object element;
        private Node   next;
        private Node   previous;

        Node(Object elementIn, Node nextNodeIn, Node prevNodeIn) {
            element = elementIn;
            next    = nextNodeIn;
            previous = prevNodeIn;
        }

        public Object getElement() {
            return element;
        }

        public Node getNext() {
            return next;
        }

        public Node getPrevious() {
            return previous;
        }

    }

    public static class DLList {
        public void addFirst(Node n) {
            SolutionDLL.Node tempNode = new SolutionDLL.Node(
                SolutionDLL.Node.this.getElement(),
                SolutionDLL.Node.this.getNext(), 
                SolutionDLL.Node.this.getPrevious()); 
            // do something
        }
    }
}

No matter if i call like this:
SolutionDLL.Node.this.getElement()
of like this:
Node.this.getElement()

I still get the error. I had the skeleton code given and this is the first time I am implementing with nested classes. So any help would be well appreciated. Thanks!

Answer 1

SolutionDLL.Node , just like any class, does not have this field. this field is only available inside object and its inner classes of that object class.

Change addFirst to get the values fomr n node instead:

public static class DLList {
   private Node firstNode = null;

    public void addFirst(Node n) {

        //do something with the first node before it is assigned to the n
        if (firstNode != null){
            SolutionDLL.Node tempNode = new SolutionDLL.Node(
            firstNode.getElement(),
            firstNode.getNext(), 
            firstNode.getPrevious()); 
         }
         firstNode = n;
        // do something
    }
}