Map集合保存值key倒序输出

//未获得Iterator对象用于迭代键

package test1;

import java.util.*;
//import java.util.Scanner;
//通过Map保存值并倒序打印

class Mycomparator implements Comparator{//自定义比较器比较
	public int compare(Object obj1,Object obj2) {
		String ele1=(String)obj1;
		String ele2=(String)obj2;
		return ele2.compareTo(ele1);//将 Number 对象与方法的参数进行比较。
	}
}
public class Main {
	public static void main(String[] args) {
	TreeMap map=new TreeMap(new Mycomparator());
	map.put("1","Lucy");
	map.put("4","Aimee");
	map.put("2","John");
	map.put("3","Smith");
	map.put("5","Amanda");
	for(Object key:map.keySet()) {//返回映射中所有 key 组成的 Set 视图。[5,4,3,2,1]
		System.out.println(key+":"+map.get(key));//get() 获取键对应的值
	}
 }		
}

结果

5:Amanda
4:Aimee
3:Smith
2:John
1:Lucy

//获得迭代键

package test1;

import java.util.*;
//import java.util.Scanner;
//通过Map保存值并倒序打印

class Mycomparator implements Comparator{//自定义比较器比较
	public int compare(Object obj1,Object obj2) {
		String ele1=(String)obj1;
		String ele2=(String)obj2;
		return ele2.compareTo(ele1);//将 Number 对象与方法的参数进行比较。
	}
}
public class Main {
	public static void main(String[] args) {
	TreeMap map=new TreeMap(new Mycomparator());
	map.put("1","Lucy");
	map.put("4","Aimee");
	map.put("2","John");
	map.put("3","Smith");
	map.put("5","Amanda");
	Set keySet=map.keySet();//获取键的集合
	Iterator it=keySet.iterator();//迭代键的集合
	//for(Object key:map.keySet()) {//返回映射中所有 key 组成的 Set 视图。[5,4,3,2,1]
	while(it.hasNext()) {
		Object key=it.next();
	System.out.println(key+":"+map.get(key));//get() 获取键对应的值
	}
 }	
}

结果

5:Amanda
4:Aimee
3:Smith
2:John
1:Lucy