How can I add a tuple (key, value) from AVL Tree to a priority queue in java?

I want to build a priority queue, where the elements are the nodes of my AVL tree. The priority queue should order the nodes with the one with the highest value first, and the one with the lowest value last. I tried to create a new class to implement it, but I'm not sure how to create it in a way that indicates that each element in the priority queue is a node in the AVL tree.

This is my code so far:

import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;

public class PriorityQueue_AVL {
    
    static class Tuple implements Comparable<Tuple>{
        String key;
        int value;
             
        public Tuple(String key, int value){
            this.key = key;
            this.value = value;
        }
     
        //@Override
        public int compareTo(Tuple node) {
            return this.value - node.value; //if positive, then this.value is larger so it goes first, and vice versa
        }

Right below the compareTo() method in the above class, I also tried to create a method that iterates through the AVL tree to add each element to the priority queue, but I’m not sure if that's how it should be done. node, key, and value are all underlined in red in the method:

    static void AVLtoPQ(){
        System.out.println();
        // push elements into priority queue PQ
        PriorityQueue<Tuple> PQ = new PriorityQueue<Tuple>();
        if (AVLTree.node != null) {
            inOrderTraversal(node.left);
            PQ.add(new Tuple(key, value));
            inOrderTraversal(node.right);    
        }
    }

This is how I'm defining the AVL tree nodes in the AVLTree.java class:

    public class AVLTree<Key extends Comparable<Key>, Value> {
    
        private Node root;  // root of the AVL tree
    
        // A node of the AVL tree
        public class Node {
            private Key key;           // key of the node
            private Value value;       // value of the node
            private Node left, right;  // left and right subtrees of the node
            private int height;        // height of the node
    
            public Node(Key key, Value value) {
                this.key = key;
                this.value = value;
                this.height = 1;
            }
        }

What's wrong with the code, and how can I fix it? I know I need to "connect" the AVLTree.java class to the PriorityQueue_AVL.java class to be able to use the object Node there, but I'm not sure how. Also, the syntax for the priority queue is off, and I can't pinpoint why.

I have a few comments to offer, based on the OP's original question and most recent reply. Since the OP doesn't seem to have a specific technical question, I'm just going to provide some commentary, in hopes of moving them forwards.

First, I would try not to get too hung up on the integration between the AVL tree and PriorityQueue. It's fine to have this as an end goal, but good implementations of most data structures will be generic enough that they can be easily modified to accept slightly different incoming data types. You can often accomplish this with generics (which it seems you are already familiar with), but good, flexible class design can also go a long way. So to start with, I would focus on creating a functional AVL tree that just stores, for example, integers, and then a functional Priority Queue that also just stores integers, and then you can worry about the extra complexity of additional types and interfacing between the two of them once the base functionality works. That is my personal philosophy though, and there are lots of other viable design strategies here as well.

Second, you said "I'm trying to create a priorityqueue class that takes a the node (a tuple) as input". I want to point out that right now, a Node is NOT a Tuple, nor are they related to each other in any way. It would also be very weird to define a method on your priority queue that accepts an instance of AVLTree::Node; this would be tightly coupling two inherently unrelated data structures together. If you wanted to extract Node to its own public class, and have it extend Tuple, or something of that nature, that is one option. But most data structure implementations you see in the real world will be standalone and will utilize either primitive or generic types for their public methods.

So to give an example, using some very rough code that will not compile, I would consider this to be a bad implementation:

public class PriorityQueue{
  private LinkedList<Integer> queue;

  // tied too tightly to a different data structure that should be unrelated
  public void addNodeToPQ(Node node){
    this.queue.addLast(node.value);  // this isn't really how you would add a value to a PriorityQueue, it's just for example
  }
}

PriorityQueue pq = new PriorityQueue();
AVLTree avlTree = new AVLTree();
pq.addNodeToPQ(avlTree.get(1));

While this implementation is cleaner and more extendable

public class PriorityQueue{
  private LinkedList<Integer> queue;

  // Uses a very basic type (Integer), rather than relying on another specialized data structure.  This allows multiple consumers to use your PriorityQueue, not just your AVLTree
  public void addValueToPQ(Integer value){
    this.queue.addLast(value); // this isn't really how you would add a value to a PriorityQueue, it's just for example
  }
}

PriorityQueue pq = new PriorityQueue();
AVLTree avlTree = new AVLTree();
pq.addValueToPQ(avlTree.get(1).value);

Regarding errors in your PriorityQueue_AVL code, I can think of 4 things I would change off the top of my head

1. No obvious reason to import HashMap, Map, or PriorityQueue in your class
2. Presumably you are going to be instantiating individual Tuple objects, so using static in the class definition is not appropriate and will not work
3. @Override should not be commented
4. You were missing a closing } for your class.

Outside of these, the code compiles just fine for me, so if there are additional syntax errors that you would like help with, some more details will be necessary.

Lastly, I do want to point out that an AVLTree (and also a PriorityQueue to some extent) is a complex data structure. If you're new to Java (and ESPECIALLY if you are new to programming in general) and you're doing this exercise purely for academic purposes, I suggest starting off by implementing something a little easier (ArrayList and LinkedList come to mind). But if that isn't the case, disregard.

If you have additional, specific questions, I (or others) are likely happy to help, but without more code or details added to your original question, I think the above is pretty much everything I have to offer.