Java 8 : Sort Array Elements By Frequency

SortArrayElementsByFrequencyProgram.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
 
public class SortArrayElementsByFrequencyProgram 
{
    private static void sortArrayElementsByFrequency(int[] inputArray)
    {
         
        Map<Integer, Integer> elementCountMap = new LinkedHashMap<>();
          
         
        for (int i = 0; i < inputArray.length; i++) 
        {
            if (elementCountMap.containsKey(inputArray[i]))
            {
                //If element is present in elementCountMap, increment its value by 1
                 
                elementCountMap.put(inputArray[i], elementCountMap.get(inputArray[i])+1);
            }
            else
            {
                //If element is not present, insert this element with 1 as its value
                 
                elementCountMap.put(inputArray[i], 1);
            }
        }
         
        //Create an ArrayList to hold sorted elements
         
        ArrayList<Integer> sortedElements = new ArrayList<>();
         
        //Java 8 code to sort elementCountMap by values in reverse order
        //and put keys into sortedElements list
         
        elementCountMap.entrySet()
                        .stream()
                        .sorted(Collections.reverseOrder(Map.Entry.comparingByValue()))
                        .forEach(entry -> { 
                            for(int i = 1; i <= entry.getValue(); i++) 
                                sortedElements.add(entry.getKey());
                                });
         
        //Printing sorted array elements in descending order of their frequency
         
        System.out.println("Input Array :"+Arrays.toString(inputArray));
         
        System.out.println("Sorted Array Elements In Descending Order Of their Frequency :");
         
        System.out.println(sortedElements);
    }
     
    public static void main(String[] args) 
    {
        sortArrayElementsByFrequency(new int[] {7, 1, 3, 4, 7, 1, 7, 1, 4, 5, 1, 9, 3});
    }
}