public class HashMapSort {public static void main(String[] args) {HashMap<Integer, Student> hashMap = new HashMap<Integer,Student>();hashMap.put(100, new Student("姚明",32));hashMap.put(2, new Student("TFboys",13));hashMap.put(30, new Student("刘翔",28));System.out.println("排序前:");System.out.println(""+hashMap.toString());System.out.println("排序后:");HashMap<Integer, Student> result  = sort(hashMap);System.out.println(""+ result);}private static HashMap<Integer, Student> sort(HashMap<Integer, Student> hashMap) {//第一步：LinkedHashMap采用的是链表结构，可以实现排序，并且是hashmap的子类//第二步：排序可以采用集合框架中的Collections.sort(list集合，比较器);//该方法可以自定义比较器//第三步：将参数hashmap转化成list集合，这一步是最关键的，hashmap有个成员函数enrtyset，可以将hashmap转化成set集合//set集合和list集合都属于collection的子类，list集合的构造函数可以是collection的子类，我们可以利用set集合构建//list集合达到我们将hashmap转化成list集合的目的//第五步：将排序之后的list集合存储在LinkedHashMap中
        LinkedHashMap<Integer, Student> linkedHashMap = new LinkedHashMap<Integer,Student>();Set<Entry<Integer, Student>> entrySet = hashMap.entrySet();ArrayList<Entry<Integer, Student>> arrayList = new ArrayList<>(entrySet);Collections.sort(arrayList,new Comparator<Entry<Integer, Student>>() {@Overridepublic int compare(Entry<Integer, Student> obj1,Entry<Integer, Student> obj2) {// TODO Auto-generated method stubreturn obj1.getValue().getAge() - obj2.getValue().getAge();}});System.out.println(""+arrayList.toString());for(int i = 0 ;i < arrayList.size(); i++){Entry<Integer, Student> entry = arrayList.get(i);linkedHashMap.put(entry.getKey(), entry.getValue());}return linkedHashMap;}
}public class Student  implements Serializable{/*** */private static final long serialVersionUID = 125252L;private transient String name = "姚明";private int age;public Student(String name, int age) {super();this.name = name;this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}@Overridepublic String toString() {return "Student [name=" + name + ", age=" + age + "]";}
}