Map扩展一对多的使用

map扩展知识。

map集合被使用是因为具备映射关系。

"yureban"   Student("01" "zhangsan");

"yureban" Student("02" "lisi");

"jiuyeban" "01" "wangwu";

"jiuyeban" "02" "zhaoliu";

一个学校有多个教室。每一个教室都有名称。

import java.util.*;
class Student
{
private String id;
private String name;
Student(String id,String name)
{
this.id = id;
this.name = name;
}
public String toString()
{
return id+":::"+name;
}
}
class  MapDemo3
{

public static void demo()
{
HashMap<String,List<Student>> czbk = new HashMap<String,List<Student>>();

List<Student> reyu = new ArrayList<Student>();
List<Student> jiuye = new ArrayList<Student>();

czbk.put("yureban",reyu);
czbk.put("jiuyeban",jiuye);

reyu.add(new Student("01","zhagnsa"));
reyu.add(new Student("04","wangwu"));
jiuye.add(new Student("01","zhouqi"));
jiuye.add(new Student("02","zhaoli"));

Iterator<String> it = czbk.keySet().iterator();

while(it.hasNext())
{
String roomName = it.next();
List<Student> room = czbk.get(roomName);

System.out.println(roomName);
getInfos(room);
}
}
public static void getInfos(List<Student> list)
{
Iterator<Student> it = list.iterator();
while(it.hasNext())
{
Student s = it.next();
System.out.println(s);
}
}
public static void main(String[] args)
{
demo();

/*
HashMap<String,List<Student>> czbk = new HashMap<String,List<Student>>();

HashMap<String,String> yure = new HashMap<String,String>();
HashMap<String,String> jiuye = new HashMap<String,String>();

czbk.put("yureban",yure);
czbk.put("jiuyeban",jiuye);

yure.put("01","zhagnsan");
yure.put("02","lisi");
jiuye.put("01","zhaoliu");
jiuye.put("02","wangwu");

//遍历czbk集合。获取所有的教室。
Iterator<String> it = czbk.keySet().iterator();

while(it.hasNext())
{
String roomName = it.next();
HashMap<String,String> room = czbk.get(roomName);

System.out.println(roomName);
getStudentInfo(room);
}
//		getStudentInfo(jiuye);
//		getStudentInfo(yure);
*/
}
public static void getStudentInfo(HashMap<String,String> roomMap)
{
Iterator<String> it = roomMap.keySet().iterator();
while(it.hasNext())
{
String id = it.next();
String name = roomMap.get(id);
System.out.println(id+":"+name);
}
}
}

————摘自《毕向东25天》