java中实现HashMap中的按照key的字典顺序排序输出

HashMap<String, String> maptest =new  HashMap<String, String>();
maptest.put("1天","day1");
maptest.put("5天","day5");
maptest.put("4天","day4");
maptest.put("2天","day2");
maptest.put("3天","day3");

Collection<String> keyset= maptest.keySet();
List<String> list = new ArrayList<String>(keyset);

//对key键值按字典升序排序
Collections.sort(list);

for (int i = 0; i < list.size(); i++) {
System.out.println("key键---值: "+list.get(i)+","+maptest.get(list.get(i)));
}