public static void main(String[] args) {
    HashMap phone = new HashMap();
    phone.put("Apple", 7299);
    phone.put("Bpple", 3000);
    phone.put("SAMSUNG", 6000);
    phone.put("Meizu", 2698);
    phone.put("Xiaomi", 2400);
    //key-sort
    Set set = phone.keySet();
    Object[] arr = set.toArray();
    Arrays.sort(arr);
    System.out.println("原hashMap为无序 转set再转array默认排序为按key排序");

    for (Object key : arr) {
        System.out.println(key + ": " + phone.get(key));
    }
    System.out.println();
    //value-sort
    List<Map.Entry<String, Integer>> sortByValueList = new ArrayList<Map.Entry<String, Integer>>(phone.entrySet());
    List<Map.Entry<String, Integer>> sortByKeyList = new ArrayList<Map.Entry<String, Integer>>(phone.entrySet());
    // 根据hashMap的Value升序排序：
    //      也等价 Collections.sort(sortByValueList, Map.Entry.comparingByValue());
    sortByValueList.sort(Map.Entry.comparingByValue());
    // 根据hashMap的Value降序排序：
    //      Collections.sort(sortByValueList, (o1, o2) -> o2.getValue().compareTo(o1.getValue()));

    //=====================================================================

    // 根据hashMap的Key排序：
    //      也等价 Collections.sort(sortByKeyList, Map.Entry.comparingByKey());
    sortByKeyList.sort(Map.Entry.comparingByKey());
    // 根据hashMap的Value降序排序：
    //      Collections.sort(sortByKeyList, (o1, o2) -> o2.getKey().compareTo(o1.getKey()));

    // 遍历
    System.out.println("按照value升序");
    for (int i = 0; i < sortByValueList.size(); i++) {
        System.out.println(sortByValueList.get(i).getKey() + ": " + sortByValueList.get(i).getValue());
    }
    System.out.println();
    System.out.println("按照key升序");
    // 遍历
    for (Map.Entry<String, Integer> mapping : sortByKeyList) {
        System.out.println(mapping.getKey() + ": " + mapping.getValue());
    }
}

原hashMap顺序(默认按照插入时间)
Apple: 7299
Bpple: 3000
Meizu: 2698
SAMSUNG: 6000
Xiaomi: 2400

按照value升序
Xiaomi: 2400
Meizu: 2698
Bpple: 3000
SAMSUNG: 6000
Apple: 7299

按照key升序
Apple: 7299
Bpple: 3000
Meizu: 2698
SAMSUNG: 6000
Xiaomi: 2400

Process finished with exit code 0

 

如果是按照key排序 且key是字符串 自然根据首字母的ASCII码来