“ 背单词 ”：界面可以再好看一点；可以去掉音标；可以改变单词显示的速度；可以增加标记生词并记到生词本中；可以增加测试的功能（单词含义可以随机选4个词的含义来让用户选择）等等。附件中有两个代码，一个单词本。参考代码见附件。

好的，根据您的要求，以下是一个简单的Java背单词程序的改进示例：

import java.util.*;

public class WordFlashcards {
    private static final int WORD_DISPLAY_SPEED = 1000; // 单词显示速度，单位为毫秒
    private static final int TEST_QUESTION_NUMBER = 4; // 测试题目数

    private Map<String, String> words; // 单词的键值对集合
    private Set<String> unknownWords; // 生词集合
    private Scanner scanner;

    public WordFlashcards() {
        words = new HashMap<>();
        unknownWords = new HashSet<>();
        scanner = new Scanner(System.in);
    }

    public void addWord(String word, String meaning) {
        words.put(word, meaning);
    }

    public void removeWord(String word) {
        words.remove(word);
    }

    public void displayWords() {
        List<String> keys = new ArrayList<>(words.keySet());
        Collections.shuffle(keys);
        for (String key : keys) {
            System.out.println("单词：" + key);
            System.out.print("中文释义：");
            String meaning = words.get(key);
            for (int i = 0; i < meaning.length(); i++) { // 控制单词显示速度
                System.out.print(meaning.charAt(i));
                try {
                    Thread.sleep(WORD_DISPLAY_SPEED);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println();
            System.out.print("是否认识这个单词？（y/n）");
            String answer = scanner.nextLine();
            if (answer.equalsIgnoreCase("n")) { // 标记生词并加入生词本
                unknownWords.add(key);
            }
        }
    }

    public void test() {
        List<String> keys = new ArrayList<>(words.keySet());
        Collections.shuffle(keys);
        int correct = 0;
        for (String key : keys) {
            String[] options = new String[TEST_QUESTION_NUMBER];
            options[0] = words.get(key); // 正确的答案
            for (int i = 1; i < TEST_QUESTION_NUMBER; i++) { // 随机选取其他三个错误答案
                String option;
                do {
                    int index = new Random().nextInt(keys.size());
                    option = words.get(keys.get(index));
                } while (option.equals(options[0]));
                options[i] = option;
            }
            Collections.shuffle(Arrays.asList(options));
            System.out.println("单词：" + key);
            for (int i = 0; i < TEST_QUESTION_NUMBER; i++) {
                System.out.println((i + 1) + ". " + options[i]);
            }
            System.out.print("请选择单词的含义（1-" + TEST_QUESTION_NUMBER + "）：");
            int choice = scanner.nextInt();
            scanner.nextLine(); // 读取换行符
            if (options[choice - 1].equals(words.get(key))) {
                System.out.println("回答正确！");
                correct++;
            } else {
                System.out.println("回答错误，正确答案为：" + words.get(key));
            }
        }
        System.out.println("测试结束，共答对 " + correct + " 个单词。");
    }

    public void displayUnknownWords() {
        if (unknownWords.isEmpty()) {
            System.out.println("生词本为空。");
        } else {
            System.out.println("生词本：");
            for (String word : unknownWords) {
                System.out.println(word + "：" + words.get(word));
            }
        }
    }

    public void saveToFile(String filename) {
        try (PrintWriter writer = new PrintWriter(filename)) {
            for (String key : words.keySet()) {
                writer.println(key + "," + words.get(key));
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    public void loadFromFile(String filename) {
        try (Scanner scanner = new Scanner(new File(filename))) {
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                String[] parts = line.split(",");
                words.put(parts[0], parts[1]);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

这个程序实现了以下功能：

1. 可以根据需要添加单词，删除单词，展示单词，并标记生词加入生词本。
2. 可以进行单词测试，随机出题，让用户选择单词的含义。
3. 可以展示生词本中的生词。
4. 可以将单词保存到文件中，并从文件中读取单词。

您可以根据需要进一步修改程序并添加界面，使程序更加易用和美观。