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("","张三1");

         javas.put("","张三2");

         hdoop.put("","张三3");

         hdoop.put("","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