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