返回组成单词的字母表的Java程序

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class WordAlphabet {
    public static void main(String[] args) {
        String word = "example";
        List<Character> alphabet = getAlphabet(word);
        System.out.println("Alphabet: " + alphabet);
    }

    public static List<Character> getAlphabet(String word) {
        char[] letters = word.toCharArray();
        Arrays.sort(letters);
        List<Character> alphabet = new ArrayList<>();
        for (int i = 0; i < letters.length; i++) {
            if (i == 0 || letters[i] != letters[i - 1]) {
                alphabet.add(letters[i]);
            }
        }
        return alphabet;
    }
}