【泛型+集合框架】 两个简单的例程

package package1;

import java.util.HashMap;
import java.util.Iterator;

public class MapDemo {
    public static void main(String[] args) {
        HashMap<String , HashMap<String , String>> school =
                new HashMap<String , HashMap<String , String>> ();
        
        HashMap<String , String> room1 = new HashMap<String , String>();
        HashMap<String , String> room2 = new HashMap<String , String>();
        
        school.put("room1",room1);
        school.put("room2",room2);
        room1.put("01", "yang");
        room1.put("02", "wang");
        room2.put("01", "sun");
        room2.put("02", "li");
        
        Iterator<String> it1 = school.keySet().iterator();
        while(it1.hasNext()){
            String room = it1.next();
            HashMap<String , String> roomm = school.get(room);
            System.out.println(room + ":" + roomm);
            getPersonInfo(roomm);
            
        }
        
        
        
    }

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

package package6;
import java.util.*;

class Student2{
    private String id;
    private String name;
    Student2(String id,String name){
        this.id=id;
        this.name=name;
    }
    public String toString(){
        return id+"   ~~   "+name;
    }
}

public class Test15 {
    public static void main(String[] args){
        HashMap<String,List<Student2>>qq=new HashMap<String,List<Student2>>();
        
        List <Student2>room1=new ArrayList<Student2>();
        List <Student2>room2=new ArrayList<Student2>();
        qq.put("first", room1);
        qq.put("second", room2);
        
        room1.add(new Student2("01", "zhang"));
        room1.add(new Student2("02", "wang"));
        room2.add(new Student2("01", "yang"));
        room2.add(new Student2("02", "chen"));
        
        Iterator<String> it=qq.keySet().iterator();
        while(it.hasNext()){
            String roomName=it.next();
            List<Student2> roomInfo=qq.get(roomName);
            System.out.println(roomName);
            getStudentInfo(roomInfo);
        }
    }
    
    
    public static void getStudentInfo(List<Student2> list){
        Iterator<Student2> it=list.iterator();
        while(it.hasNext()){
         Student2 s=it.next();
            System.out.println(s);
        }
    }
}