Map类的三种实现 <个人练习>

package cn.zmh.zuoye;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/*
* 定义
*   aaa学校
*     定义两个班级
*        java班  学号，姓名
*            001  张三1
*            002  张三2
*        hdoop班 学号，姓名
*            001  张三3
*            002  张三4
* */
public class MapDemo1 {
    public static void main(String[] args) {
        Map<String,String> javas = new HashMap<>();
        Map<String,String> hdoop = new HashMap<>();
        // 键值不能重复
        javas.put("001","张三1");
        javas.put("002","张三2");
        hdoop.put("001","张三3");
        hdoop.put("002","张三4");
        Map<String,Map<String,String>> aaa = new HashMap<>();
        aaa.put("java班",javas);
        aaa.put("hdoop班",hdoop);
        //调用方法 传参
        fun1(aaa);
    }
    //第一种  迭代器 Iterator        entrySet();
    public  static void fun1(Map<String, Map<String, String>> aaa) {
        Set<Map.Entry<String,Map<String,String>>> classNameSet = aaa.entrySet();
        Iterator<Map.Entry<String,Map<String,String>>> it = classNameSet.iterator();
        while(it.hasNext()){
            Map.Entry<String, Map<String, String>> next = it.next();
            String classNamekey = next.getKey();
            Map<String, String> classNameValue = next.getValue();
            System.out.println(classNamekey);
            Set<Map.Entry<String, String>> studentSet = classNameValue.entrySet();
            Iterator<Map.Entry<String,String>> studendIt = studentSet.iterator();
            while (studendIt.hasNext()){
                Map.Entry<String, String> next1 = studendIt.next();
                String studentkey = next1.getKey();
                String studendValue = next1.getValue();
                System.out.println("\t"+studentkey+":"+studendValue);
            }
        }
    }
    //第二种  增强for循环    entrySet();
    public static void fun2(Map<String, Map<String, String>> aaa) {
        Set<Map.Entry<String, Map<String, String>>> classNameSet = aaa.entrySet();
        for(Map.Entry<String,Map<String,String>> i:classNameSet){
            String classNamekey = i.getKey();
            Map<String, String> classNameValue = i.getValue();
            System.out.println(classNamekey);
            Set<Map.Entry<String, String>> studentSet = classNameValue.entrySet();
            for(Map.Entry<String, String> i1:studentSet){
                String studentkey = i1.getKey();
                String studentValue = i1.getValue();
                System.out.println("\t"+studentkey+":"+studentValue);
            }
        }
    }
    //第三种 迭代器 Iterator     方法keySet();
    public static void fun3(Map<String, Map<String, String>> aaa) {
        Set<String> classNameSet = aaa.keySet();
        Iterator<String> it = classNameSet.iterator();
        while (it.hasNext()){
            String classNameKey = it.next();
            Map<String, String> classNameValue = aaa.get(classNameKey);
            System.out.println(classNameKey);
            //System.out.println(classNameValue);
            Set<String> studentSet = classNameValue.keySet();
            Iterator<String> it1 = studentSet.iterator();
            while (it1.hasNext()){
                String studentKey = it1.next();
                //System.out.println(studentKey);
                String studentValue = classNameValue.get(studentKey);
                System.out.println(studentKey+":"+studentValue);
            }
        }
    }
}

 打印结果