Sorting HashMap By Key And Value + Java 8

Hi All,

Greeting of the day!

Today we will see how we can sort HashMap by both key & value. Also, we will explore how we can sort HashMap using java 8.

• To sort HashMap by key we can simply put HashMap data in TreeMap.
• To sort HashMap by the value we have to follow 3 steps
• Create LinkedList from Map.
• Sort List by value using Comparator.
• Create Map from the sorted list.  

So let's start

package com.demo; import java.util.Collections; import java.util.Comparator; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.LinkedList; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.TreeMap; public class SortingHashMap { public static void main(String[] args) { Map<String, Integer> map = new HashMap<String, Integer>(); map.put("Rajesh", 2); map.put("Suresh", 1); map.put("Pratik", 3); map.put("Ankit", 4); //Sort HashMap by Key TreeMap<String, Integer> sortedMap = new TreeMap<>(); sortedMap.putAll(map); System.out.println("Sorted Map By Key "+sortedMap); //Sort HashMap by Value //Step 1 Create LinkedList from Map List<Map.Entry<String, Integer>> list = new LinkedList<>(map.entrySet()); //Step 2 Sort List by value using Comparator. Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() { @Override public int compare(Entry<String, Integer> object1, Entry<String, Integer> object2) { return object1.getValue().compareTo(object2.getValue()); } }); //Step 3 Create Map from sorted list. Map<String, Integer> sortedMapByValue = new LinkedHashMap<>(); list.forEach(x -> sortedMapByValue.put(x.getKey(), x.getValue())); System.out.println("Sorted Map By Value "+sortedMapByValue); } }

Below will be our output.

Sorted Map By Key {Ankit=4, Pratik=3, Rajesh=2, Suresh=1} Sorted Map By Value {Suresh=1, Rajesh=2, Pratik=3, Ankit=4}

Now let's see how to sort HashMap by key using java 8

map.entrySet().stream().sorted(Map.Entry.comparingByKey()) .forEach(x->System.out.println(x));

Now let's see how to sort HashMap by value using java 8

map.entrySet().stream().sorted(Map.Entry.comparingByValue()) .forEach(x->System.out.println(x));

Below is a complete program for reference.

package com.demo; import java.util.HashMap; import java.util.Map; public class SortingHashMap { public static void main(String[] args) { Map<String, Integer> map = new HashMap<String, Integer>(); map.put("Rajesh", 2); map.put("Suresh", 1); map.put("Pratik", 3); map.put("Ankit", 4); System.out.println("Sorted Map By Key "); map.entrySet().stream().sorted(Map.Entry.comparingByKey()) .forEach(x->System.out.println(x)); System.out.println("Sorted Map By Values "); map.entrySet().stream().sorted(Map.Entry.comparingByValue()) .forEach(x->System.out.println(x)); } }

Below is output

Sorted Map By Key Ankit=4 Pratik=3 Rajesh=2 Suresh=1 Sorted Map By Values Suresh=1 Rajesh=2 Pratik=3 Ankit=4

Let me know if you have any questions.

Also, you can refer below useful post

Sorting Array List In Ascending & Descending Order + Java 8 + Sorting Array List Of Custom Object

Sorting HashSet In Ascending & Descending order + Java 8

Comparator and Comparable In Java + Difference Between Comparator and Comparable + Java 8

Java 8 Stream - Terminal Operations With Examples

Java 8 Stream - Intermediate Operations With Examples

For spring refer to Spring Tutorial

Thank you

Happy Learning!