How can we sort a Map by both key and value using lambda in Java?

A Map interface implements the Collection interface that provides the functionality of the map data structure. A Map doesn't contain any duplicate keys and each key is associated with a single value. We can able to access and modify values using the keys associated with them.

In the below two examples, we can able to sort a Map by both key and value with the help of lambda expression.

Example for sorting of Map using Key

import java.util.*;
import java.util.stream.*;

public class MapSortUsingKeyTest {
   public static void main(String args[]) {
     
      // Sort a Map by their key
      Map<Integer, String> map = new HashMap<Integer, String>();

      map.put(2, "India");
      map.put(5, "Australia");
      map.put(3, "England");
      map.put(1, "Newzealand");
      map.put(4, "Scotland");

      Map<Integer, String> sortedMap = map.entrySet().stream()
                               .sorted(Map.Entry.comparingByKey())
                               .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
                               (e1, e2) -> e2, LinkedHashMap::new));
      System.out.println("Sorted Map: " + Arrays.toString(sortedMap.entrySet().toArray()));
   }
}

Output

Sorted Map: [1=Newzealand, 2=India, 3=England, 4=Scotland, 5=Australia]

Example for sorting of Map using Value

import java.util.*;
import java.util.stream.*;

public class MapSortUsingValueTest {
   public static void main(String args[]) {
     
      //Sort a Map by their Value
      Map<Integer, String> map = new HashMap<Integer, String>();

      map.put(1, "Jaidev");
      map.put(2, "Adithya");
      map.put(3, "Vamsi");
      map.put(4, "Krishna");
      map.put(5, "Chaitanya");

      Map<Integer, String> sortedMap = map.entrySet().stream()
                               .sorted(Map.Entry.comparingByValue())
                               .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
                               (e1, e2) -> e2, LinkedHashMap::new));
      System.out.println("Sorted Map: " + Arrays.toString(sortedMap.entrySet().toArray()));
   }
}

Output

Sorted Map: [2=Adithya, 5=Chaitanya, 1=Jaidev, 4=Krishna, 3=Vamsi]

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Updated on: 14-Jul-2020

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