Example: Array Element Frequency using HashMap in Java

// Array Element Frequency using HashMap
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        // Step 1: Initialize the array
        int[] arr = {10, 20, 20, 10, 10, 30, 40, 50, 20, 40};

        // Step 2: Create a HashMap to store element frequencies
        // The key will be the array element, and the value will be its count.
        Map<Integer, Integer> frequencyMap = new HashMap<>();

        // Step 3: Iterate through the array and update frequencies in the map
        for (int element : arr) {
            // Using getOrDefault to simplify logic:
            // If element exists as a key, get its current count and increment.
            // If element does not exist, default count to 0 and then increment to 1.
            frequencyMap.put(element, frequencyMap.getOrDefault(element, 0) + 1);
        }

        // Step 4: Print the frequencies from the HashMap
        System.out.println("Element Frequencies:");
        for (Map.Entry<Integer, Integer> entry : frequencyMap.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue() + " times");
        }
    }
}