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In this programming tutorial you will learn writing Java Program to find the frequency of each elements given in Array. To find the counting of each elements we can take a help of another array where we will store the frequency of each elements.

For example:

Given array arr = [1, 3, 3, 4, 2, 3, 3, 2, 6, 6]

So output will be like

1 -> 1

3 -> 4

4 -> 1

2 -> 2

6 -> 2

Program 1 : Find the frequency of array elements in Java

import java.util.Arrays;
import java.util.*; 
class Main
{
    public static void main(String []args)
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Java Program to count frequency of elements");
        System.out.print("Enter the size of array: ");
        int size = sc.nextInt();
        int arr[] = new int[size];
        for(int i=0; i<size; i++) {
            System.out.print("Please give value for index "+ i +" : ");
            arr[i] = sc.nextInt();
        } 
        boolean visited[] = new boolean[size];
        Arrays.fill(visited, false);
        for (int i = 0; i < size; i++) {
            if (visited[i] == true)
                continue;
            int count = 1;
            for (int j = i + 1; j < size; j++) {
                if (arr[i] == arr[j]) {
                    visited[j] = true;
                    count++;
                }
            }
            System.out.println(arr[i] + " " + count);
        }
    }
}

Output

Java Program to count frequency of elements
Enter the size of array: 5
Please give value for index 0 : 2
Please give value for index 1 : 3
Please give value for index 2 : 4
Please give value for index 3 : 4
Please give value for index 4 : 2
2 2
3 1
4 2

Program 2 : Find frequency of array elements using recursion

import java.util.Arrays;
import java.util.*; 
class Main
{
    public static void main(String []args)
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("Java Program to count frequency of elements");
        System.out.print("Enter the size of array: ");
        int size = sc.nextInt();
        int arr[] = new int[size];
        for(int i=0; i<size; i++) {
            System.out.print("Please give value for index "+ i +" : ");
            arr[i] = sc.nextInt();
        } 
        Map<Integer, Integer>map = new HashMap<>();
        for (int i = 0; i <size; i++)
        {
            if (map.containsKey(arr[i]))
            {
                map.put(arr[i], map.get(arr[i]) + 1);
            }
            else
            {
                map.put(arr[i], 1);
            }
        }
        System.out.println("Frequency of array elements are : ");
        for (Map.Entry<Integer, Integer> entry : map.entrySet())
        {
            System.out.println(entry.getKey() + " " + entry.getValue());
        }
    }
}

Output

Java Program to count frequency of elements
Enter the size of array: 6
Please give value for index 0 : 1
Please give value for index 1 : 2
Please give value for index 2 : 1
Please give value for index 3 : 3
Please give value for index 4 : 3
Please give value for index 5 : 3
Frequency of array elements are : 
1 2
2 1
3 3