在SharedPreferences中存储列表或集

// 将列表转换为字符串
private String listToString(List<String> list) {
    StringBuilder sb = new StringBuilder();
    for (String s : list) {
        sb.append(s).append(",");
    }
    return sb.toString();
}

// 将字符串转换为列表
private List<String> stringToList(String s) {
    List<String> list = new ArrayList<>();
    if (!TextUtils.isEmpty(s)) {
        String[] arr = s.split(",");
        for (String item : arr) {
            if (!TextUtils.isEmpty(item)) {
                list.add(item);
            }
        }
    }
    return list;
}

// 保存字符串列表
private void saveList(Context context, String key, List<String> list) {
    SharedPreferences sp = context.getSharedPreferences("my_shared_preferences", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sp.edit();
    editor.putString(key, listToString(list));
    editor.apply();
}

// 读取字符串列表
private List<String> readList(Context context, String key) {
    SharedPreferences sp = context.getSharedPreferences("my_shared_preferences", Context.MODE_PRIVATE);
    String s = sp.getString(key, "");
    return stringToList(s);
}