两种不同分HashMap扩展的方法

import java.util.*;

class  hashMapDemo3
{
    public static void main(String[] args) 
    {
        
        HashMap<String,String> groupA = new HashMap<String,String>();
        groupA.put("ben","01");
        groupA.put("sam","02");
        groupA.put("edison","03");
        groupA.put("nancy","04");
        
        HashMap<String,String> groupB = new HashMap<String,String>();
        groupB.put("Btusom","01");
        groupB.put("Bsammy","02");
        groupB.put("Beson","03");
        groupB.put("Bnanny","04");
        
        HashMap<String,HashMap<String,String>> itcast = new HashMap<String,HashMap<String,String>>();
        itcast.put("groupA",groupA);
        itcast.put("groupB",groupB);
        
        Iterator<String> it = itcast.keySet().iterator();
        while(it.hasNext())
        {
            String id = it.next();
            HashMap<String,String> group = itcast.get(id);
            groupInfo(group);
        }
        //System.out.println("Hello World!");
    }

    public static void groupInfo(HashMap<String,String> hm)
    {
        Iterator<String> it = hm.keySet().iterator();
        while(it.hasNext())
        {
            String id = it.next();
            String name = hm.get(id);
            System.out.println(id+" "+name);
        }
    }
}

public static void getInfos(List<Student> list)
    {
        Iterator<Student> it = list.iterator();
        while(it.hasNext())
        {
            Student s = it.next();
            System.out.println(s);
        }
    }