Hello I need assistance with checking the invariant in the w

Hello, I need assistance with checking the invariant in the wellFormed method. The cases are in the comments within the code.

public class TreeMap<K,V> extends AbstractMap<K,V> {

   // Here is the data structure to use.
  
   private static class Node<K,V> extends AbstractEntry<K,V> {
       Node<K,V> left, right;
       Node<K,V> parent;
       Node(K k, V v) {
           super(k,v);
           parent = left = right = null;
       }
   }
  
   private Comparator<K> comparator;
   private Node<K,V> dummy;
   private int numItems = 0;
   private int version = 0;

   private boolean wellFormed() {

       // 1. check that comparator is not null
       // 2. check that dummy is not null
       // 3. check that dummy\'s right subtree and parent are null
       // 4. check that all (non-dummy) nodes are in range
       // 5. check that each (non-dummy) node\'s parent reference is correct
       // 6. check that number of items matches number of (non-dummy) nodes
       return true;
   }

Solution

package com.tree;

import java.util.Comparator;
import java.util.TreeMap;

public class MyTreeMapComparator {

   private static class Node<K,V> extends AbstractEntry<K,V> implements Comparator<String>{
        Node<K,V> left, right;
        Node<K,V> parent;
        Node(K k, V v) {
            super(k,v);
            parent = left = right = null;
        }
      
        @Override
        public int compare(String str1, String str2) {
            return str1.compareTo(str2);
        }
    }
   
    public static void main(String a[]){
        //the treemap sorts by key
       Node <String, String> node0= new Node<String, String>(\"java\",\"language\");
       Node <String, String> node1= new Node<String, String>(\"computer\",\"machine\");
       Node <String, String> node2= new Node<String, String>(\"india\",\"country\");
       Node <String, String> node22= new Node<String, String>(\"USA\",\"country\");
       node2.left=node22;
       node0.left=node1;
       node0.right=node2;
      
       if(node0!=null)
        System.out.println(node0);
    }
}

class MyComp implements Comparator<String>{

    @Override
    public int compare(String str1, String str2) {
        return str1.compareTo(str2);
    }
   
}

Program2:

package com.tree;

public class AbstractEntry<T1, T2> {

public AbstractEntry() {
      
   }
   public AbstractEntry(T1 k, T2 v) {
      
   }
}