Sorting HashMap by value

In this post, We are going to discuss
one of the most common Java Interview Program to sort HashMap by value.
HashMap store the data in the form of key and value pair where the key can not be duplicate.

Steps:

• Converted the HashMap into Set storing Entry.
• Created the comparator to sort the entry based on value.
• Converted the Set to List.
• Collections.sort() is used to sort the list.

Code:

HashMapSort.java

package com.javainstance;

import java.util.ArrayList;

import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map.Entry;
import java.util.Set;

/**
 * @author javainstance
 *
 */
public class HashMapSort {

public static void main(String[] args) {
HashMap<String, Integer> unsortedMap = new HashMap<>();
unsortedMap.put("Sachin", 3);
unsortedMap.put("Rahul", 7);
unsortedMap.put("Sourav", 11);
unsortedMap.put("Laxman", 5);
unsortedMap.put("Virender", 2);
unsortedMap.put("Zaheer", 9);

printSortedHashMap(unsortedMap);

}

/**
* @param inputMap
*/
public static void printSortedHashMap(HashMap<String, Integer> inputMap) {

Set<Entry<String, Integer>> mapEntries = inputMap.entrySet();

List<Entry<String, Integer>> entriesList = new ArrayList<>(mapEntries);
MapSortComparator mapSort = new MapSortComparator();
Collections.sort(entriesList, mapSort);
for (Entry<String, Integer> entry : entriesList) {
System.out.println("Key--" + entry.getKey() + "--Value--" + entry.getValue());
}

}
}

/**
 * Comparator class to sort on value
 *
 * @author javainstance
 *
 */
class MapSortComparator implements Comparator<Entry<String, Integer>> {

@Override
public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) {
// TODO Auto-generated method stub
return o1.getValue() - o2.getValue();
}

}

Output:

Key--Viraj--Value--2
Key--Sarc--Value--3
Key--Lavan--Value--5
Key--Rajesh--Value--7
Key--Zaik--Value--9
Key--Sourav--Value--11

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