HashMap的两种取出方式

public class Demo{
    public static void main(String[] args){
        Map<Student,String> map = new HashMap<Student,String>();
        map.put(new Student("Kevin",21),"重庆");
        map.put(new Student("Litch",21),"四川");
        map.put(new Student("Rocco",24),"江西");
        map.put(new Student("Lenka",21),"广东");
        //----------第一种keySet
        Set<Student> set = map.keySet();
        Iterator<Student> it = set.iterator();
        while(it.hasNext()){
            System.out.println(map.get(it.next()));
        }
        //-----------第二种取出方式entrySet
        Set<Map.Entry<Student,String>> s = map.entrySet();
        Iterator<Entry<Student, String>> its = s.iterator();
        while(its.hasNext()){
            Map.Entry<Student, String> ma = (Map.Entry<Student, String>)its.next();
            System.out.println(ma.getKey()+"--"+ma.getValue());
        }
    }
}