我在java中创建了一个密码破解程序，可以破解文本文件列表中的密码。然后，它生成一个字典，其中包含以下对：散列的单词和原始单词。我正在寻找一种加速程序的方法，让它从文件中读取所有单词，然后使用多线程生成哈希。如何将单词列表分解成四个独立的分区，然后在createdictionary方法中对其进行多线程操作？到目前为止，我掌握的情况如下：

public class Main {
    private static final String FNAME = "words.txt";
    private final static String PASSWDFNAME = "passwd.txt";
    private static Map<String, String> dictionary = new HashMap<>();

    public static void main(String[] args) {
        // Create dictionary of plain / hashed passwords from list of words
        System.out.println("Generating dictionary ...");
        long start = System.currentTimeMillis();
        createDictionary(FNAME);
        System.out.println("Generated " + dictionary.size() + " hashed passwords in dictionary");
        long stop = System.currentTimeMillis();
        System.out.println("Elapsed time: " + (stop - start) + " milliseconds");

        // Read password file, hash plaintext passwords and lookup in dictionary
        System.out.println("\nCracking password file ...");
        start = System.currentTimeMillis();
        crackPasswords(PASSWDFNAME);
        stop = System.currentTimeMillis();
        System.out.println("Elapsed time: " + (stop - start) + " milliseconds");
    }

    private static void createDictionary(String fname) {
        // Read in list of words
        List<String> words = new ArrayList<>();
        try (Scanner input = new Scanner(new File(fname));) {
            while (input.hasNext()) {
                String s = input.nextLine();
                if (s != null && s.length() >= 4) {
                    words.add(s);
                }
            }
        } catch (FileNotFoundException e) {
            System.out.println("File " + FNAME + " not found");
            e.printStackTrace();
            System.exit(-1);
        }

        // Generate dictionary from word list
        for (String word : words) {
            generateHashes(word);
        }
    }

    private static void crackPasswords(String fname) {
        File pfile = new File(fname);
        try (Scanner input = new Scanner(pfile);) {
            while (input.hasNext()) {
                String s = input.nextLine();
                String[] t = s.split(",");
                String userid = t[0];
                String hashedPassword = t[1];
                String password = dictionary.get(hashedPassword);
                if (password != null) {
                    System.out.println("CRACKED - user: "+userid+" has password: "+password);
                }
            }
        } catch (FileNotFoundException ex) {
            System.out.println(ex.getMessage());
            ex.printStackTrace();
            System.exit(-1);
        }
    }

    private static void generateHashes(String word) {
        // Convert word to lower case, generate hash, store dictionary entry
        String s = word.toLowerCase();
        String hashedStr = HashUtils.hashPassword(s);
        dictionary.put(hashedStr, s);
        // Capitalize word, generate hash, store dictionary entry
        s = s.substring(0, 1).toUpperCase() + s.substring(1);
        hashedStr = HashUtils.hashPassword(s);
        dictionary.put(hashedStr, s);
    }
}