程式碼展示 

    @Test
    public void test23(){
        Set<String> set = new HashSet<>();
        set.add("aaaa");
        set.add("qqqq");
        set.add("wwww");
        set.add("eeee");

        List<String> list = new ArrayList<>(set);
        // 將集合轉換成以逗號分隔的字串
        String str = String.join(",", list);
        System.out.println(str);
        // 將字串轉換成集合
        List<String> asList = Arrays.asList(str.split(","));
        asList.forEach(str1 -> System.out.println(str1));

    }
 

結果展示 

qqqq
wwww
aaaa
eeee

Process finished with exit code 0