Select a Map Collection to save the number (key) and name (value) of students with numbers from 1 to 15

Keywords: Java

Select a Map collection to hold the number (key) and name (value) of students with numbers from 1 to 15.
*Student numbers are represented as strings and entered in a random order in the Map collection.
* The elements in the Map collection are then printed in order of the number from largest to smallest.
*You need to customize the Comparator of the Map collection because the size comparison of string objects is in dictionary order, not the corresponding numeric value.

Requirements: You must sort using the internal sorting mechanism of the Map collection, not externally.

import java.util.*;  
public class Test {  
    public static void main(String[] args) {  
        //Create map object  
        TreeMap tm  =new TreeMap(new MyComparator());  
        //Store keys and values  
        tm.put("1006", "Zhenghuan");  
        tm.put("1003", "Sub-ink");  
        tm.put("1002", "Boyi");  
        tm.put("1004", "In Van");  
        tm.put("1005", "Yanbin");  
        tm.put("1015", "a fine piece of jade");  
        tm.put("1001", "Enchang");  
        tm.put("1009", "Zhenxi");  
        tm.put("1010", "Ji-Hee");  
        tm.put("1008", "Sheng En");  
        tm.put("1014", "Young Forest");  
        tm.put("1011", "Zhenxian");  
        tm.put("1007", "Smart");  
        tm.put("1012", "Xiaolin");  
        tm.put("1013", "Sensitivity");  
        //Get a collection of keys  
        Set keySet=tm.keySet();  
        //Get Iterator Object  
        Iterator it=keySet.iterator();  
        while(it.hasNext()) {  
            //Get Key Value  
            //Get the value for the key  
            Object value=tm.get(key);  
            //Output keys and values  
            System.out.println(key +":"+value);  
    /* Or access keys and values through foreach 
         for(Object key: tm.keySet()){ 
         System.out.println(key+" "+tm.get(key)); 
//Custom Comparator MyComparator  
class MyComparator implements Comparator{  
    public int compare(Object b1, Object b2) {  
        String s1=(String)b1;  
        String s2=(String)b2;  
        return s2.compareTo(s1);  

Posted by joebWI on Fri, 03 Jul 2020 09:25:27 -0700