compareTo冒泡比较时间字符串

public static void main(String[] args) {
        List<String> dates = new ArrayList<String>();
        dates.add("2018-06-01");
        dates.add("2018-05-23");
        dates.add("2018-05-06");
        dates.add("2018-01-06");
        dates.add("2018-05-20");
        Map<String, String> data = new HashMap<String, String>();
        data.put("2018-06-01", "lws");
        data.put("2018-05-23", "sss");
        data.put("2018-05-06", "www");
        data.put("2018-01-06", "sl1");
        data.put("2018-05-20", "lll");

        String[] array =new String[dates.size()];
        dates.toArray(array);
        for (int i = 0; i < array.length - 1; i++) {
            for (int j = 0; j < array.length- i - 1; j++) {
                if (array[j].compareTo(array[j + 1]) > 0) {
                    String temp = array[j];
                    array[j] = array[j + 1];
                    array[j + 1] = temp;
                }
            }
        }
        System.out.println(data.get(array[0]));
}