Map sorted by Value

Map can't be sorted by value

Map can't be sorted by value , so that we can change map to List and then sort the list .

Collections.sort( List list , Comparator<? super T> c)

In order to keep simple style of coding , we can add the Comparator out ot main class .

class listCompare implements Comparator< Map.Entry<String,Integer> >{
            public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
           
      // Must apply compareTo() functin , to have more security .
      return o1.getValue().compareTo(o2.getValue());     
    }
}

Code

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

public class mapSortByValue{
    public static void main(String [] args){
        
        // New a Map
        
        Map<String, Integer > map = new TreeMap<String , Integer >();
        map.put("A", 4);
        map.put("C", 2);
        map.put("B", 1);
        map.put("D", 3);
        
        // Change Map to List
        
        List<Map.Entry<String,Integer> > list = new ArrayList<Map.Entry<String,Integer> >(map.entrySet());
        
        // Sorting ...
        
        Collections.sort(list, new listCompare());
        
        // print
        
        for(Map.Entry<String ,Integer >  one:list){
            System.out.println(one.getKey() + ":" + one.getValue() );
        }
        
    }    
}
class listCompare implements Comparator<Map.Entry<String , Integer > > {

    public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
        return o1.getValue().compareTo(o2.getValue());
    }
    
}

B:1
C:2
D:3
A:4