java : sort list of map by multiple key

package homeWork;
import java.util.ArrayList;

import java.util.Comparator;

import java.util.HashMap;

import java.util.List;

import java.util.Map;
public class sortSample001 {
	public static void main(String[] args) {

		

		List> countries = new ArrayList>();

		Map country;

		country = new HashMap();

		country.put( "name",       "japan" );

		country.put( "currency",   "JPY" );

		country.put( "population", 127156000 );

		countries.add( country );
		country = new HashMap();

		country.put( "name", "france" );

		country.put( "currency", "EUR" );

		country.put( "population", 65073482 );

		countries.add( country );

		

		country = new HashMap();

		country.put( "name",       "japan" );

		country.put( "currency",   "JPY" );

		country.put( "population", 56000 );

		countries.add( country );


		country = new HashMap();

		country.put( "name", "spain" );

		country.put( "currency", "EUR" );

		country.put( "population", 44904000 );

		countries.add( country );
		country = new HashMap();

		country.put( "name", "russia" );

		country.put( "currency", "RUB" );

		country.put( "population", 141903979 );

		countries.add( country );

		

		for(Mapct:countries) {

			System.out.println(ct.get("name")+":"+ct.get("population"));

		}

		System.out.println("-----------------------");

		

		Comparator >  c1 =Comparator.comparing (m -> (String) m.get("name"));

		Comparator >  c2 =Comparator.comparing (m -> (Integer) m.get("population"));

		Comparator >  c = c1.thenComparing(c2);

		countries.sort(c);

		

		for(Mapct:countries) {

			System.out.println(ct.get("name")+":"+ct.get("population"));	

		}

	}	

}
result
japan:127156000

france:65073482

japan:56000

spain:44904000

russia:141903979












































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france:65073482

japan:56000

japan:127156000

russia:141903979

spain:44904000