Word Ladder assignment

WordLadder.java

package org.example;

import java.io.File;
import java.io.FileNotFoundException;
import java.net.URISyntaxException;
import java.util.*;

public class Main {

    private static final Queue<Stack<String>> stackQueue = new LinkedList<>();
    private static final Set<String> visitedWords = new HashSet<>();

    public static void main(String[] args) throws FileNotFoundException, URISyntaxException {
        var result = findWordLadder("code", "data", "FoursDictionary.txt");
        System.out.println(result);
    }

    private static WordsDictionary getDictionary(String fileName) throws URISyntaxException, FileNotFoundException {
        var dictionaryFile = new File(Objects.requireNonNull(Main.class.getClassLoader().getResource(fileName)).toURI().getPath());
        return new WordsDictionary(dictionaryFile);
    }

    public static Stack<String> findWordLadder(String beginWord, String endWord, String dictionaryFileName) throws FileNotFoundException, URISyntaxException {

        var dictionary = getDictionary(dictionaryFileName);

        Stack<String> initialStack = new Stack<>();
        initialStack.add(beginWord);
        visitedWords.add(beginWord);
        stackQueue.add(initialStack);

        while(!stackQueue.isEmpty()){
            var stack = stackQueue.poll();
            var topWord = stack.peek();

            if(topWord.equals(endWord)){
                return stack;
            }

            var n = topWord.length();

            for (var i=0; i<n; i++) {
                for(var j='a'; j<='z'; j++) {
                    if(topWord.charAt(i) == j)
                        continue;

                    var newWord = topWord.replace(topWord.charAt(i), j);
                    if(!dictionary.contains(newWord) || visitedWords.contains(newWord))
                        continue;

                    var newStack = (Stack<String>) stack.clone();
                    newStack.push(newWord);
                    stackQueue.add(newStack);
                    visitedWords.add(newWord);
                }
            }
        }
        return new Stack<>();
    }
}