How to sort the contents in Map based on values?

If you want to sort the map based on Values .

Below is the sample code

Example : In the below example  key is student name , Value is Student marks

Map<String, Integer> studentToTotal = new TreeMap<String, Integer>();

If you want to sort the studentname(key) based on mark(value) . First you have to convert the mapbject


List<Entry<String, Integer>> list = new ArrayList<Entry<String, Integer>>(
                studentToTotal.entrySet());

then use Collections sort method

Collections.sort( list, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Map.Entry<String, Integer> o1,
                    Map.Entry<String, Integer> o2) {
                return (o2.getValue()).compareTo(o1.getValue());
            }
        }       );

The above method will sort the student name based on highest total to lowest total.
 
If you want to sort the student name based on lowest totatl to highest total below is the code snippet

 
Collections.sort( list, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Map.Entry<String, Integer> o1,
                    Map.Entry<String, Integer> o2) {
                return (o1.getValue()).compareTo(o2.getValue());
            }
        }       );


Example program to sort the student name based on highest total to lowest total

package com.awf.org;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
import java.util.List;

public class SortingBasedOnMapValues {

    public static void main(String[] args) {
       
       // studentToTotal map key is student name ,value is student total

        Map<String, Integer> studentToTotal = new TreeMap<String, Integer>();

        List<Entry<String, Integer>> sortedlistdsc = new ArrayList<Entry<String, Integer>>();
       
        studentToTotal.put("awf-Tamil", 1000);
        studentToTotal.put("awf-Tirumala", 986);
        studentToTotal.put("awf-Joel", 999);
        studentToTotal.put("awf-Rahul", 984);
        studentToTotal.put("awf-Arun", 987);

       
           
        sortedlistdsc=sortStudentsBasedOnTotal(studentToTotal);
       
        System.out.println("Student details based on highest to lowest Total ");

        for (Entry<String, Integer> entry : sortedlistdsc{
            System.out.println("Name ::" + entry.getKey()
                    + "\tTotal ::" + entry.getValue() + "\n");
        }
   
 }

  
   
    public static List<Entry<String, Integer>> sortStudentsBasedOnTotal(
            Map<String, Integer> studentToTotalref) {

        // Sort the cells based on Student marks
       // put the studenttotal map entry set in list using the below command for sorting

        List<Entry<String, Integer>> list = new ArrayList<Entry<String, Integer>>(
                studentToTotalref.entrySet());

        Collections.sort( list, new Comparator<Map.Entry<String, Integer>>() {
            public int compare(Map.Entry<String, Integer> o1,
                    Map.Entry<String, Integer> o2) {
                return (o2.getValue()).compareTo(o1.getValue());
            }
        }       );

        return list;

    }
   

}
=======================================================================

Output :

Student details based on highest to lowest Total

Name ::awf-Tamil         Total ::1000
Name ::awf-Joel            Total ::999
Name ::awf-Arun           Total ::987
Name ::awf-Tirumala    Total ::986
Name ::awf-Rahul          Total ::984

Regards,

R Tamilanban M.E(CSE)

AWF Community