上干货~

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题文要求:
//集合嵌套之HashMap嵌套HashMap


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import java.util.HashMap;


public class Test04 {
        public static void main(String[] args) {
                HashMap<Student, String> hm = new HashMap<>();
                hm.put(new Student("李天",53), "深圳");
                hm.put(new Student("崔斯特",12), "北京");
                hm.put(new Student("疾风剑豪",23), "西安");
                hm.put(new Student("科特",23), "诺克萨斯");
               
                HashMap<Student, String> hm1 = new HashMap<>();
                hm1.put(new Student("红葫芦",11), "深山老林");
                hm1.put(new Student("紫葫芦",12), "深山老林北京");
                hm1.put(new Student("绿葫芦",13), "深山老林西安");
                hm1.put(new Student("黄葫芦",14), "深山老林诺克萨斯");
       
                HashMap<HashMap<Student, String>, String> hm3 = new HashMap<>();
                hm3.put(hm, "英雄联盟");
                hm3.put(hm1, "葫芦兄弟");
               
                for (HashMap<Student, String> a : hm3.keySet()) {
                        String value = hm3.get(a);
                        for (Student aa : a.keySet()) {
                                String value1 = a.get(aa);
                                System.out.println(value+"="+value1+"NAME:"+aa.getName()+",AGE:"+aa.getAge());
                        }
                }
        }
}


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总结:

关于嵌套问题,只要记住  
外层嵌套里面的绝对是 个 hashmap,
这样在写,外层嵌套 的 键的时候就非常的清晰了,
主要就是要求写出那个键,
只要键问题可以搞清楚是谁,
那么问题    就迎刃而解

package dao;

import java.util.HashMap;
import java.util.Set;

public class HashMapExc 
{
public static void main(String[] args)
{
HashMap map1=new HashMap();
HashMap map2=new HashMap();
map2.put("1", "a");
map2.put("2", "b");
map2.put("3", "c");

map1.put("0", map1);

Set keys=map2.keySet();
Object keyArray[]=keys.toArray();

HashMap map=(HashMap)map1.get("0");

for(int i=0;i<keyArray.length;i++)
{
System.out.println(map2.get(""+(i+1)));

}
}
}