Example: CharacterFrequencyHashMap in Java

// CharacterFrequencyHashMap
import java.util.HashMap;
import java.util.Map;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        String str = "programming";
        Map<Character, Integer> charFrequencies = new HashMap<>();

        // Step 1: Iterate through each character of the string
        for (char c : str.toCharArray()) {
            // Step 2: Use getOrDefault to safely increment count
            // If character 'c' is already in the map, get its count and add 1.
            // If not, get 0 (default value) and add 1, then put it into the map.
            charFrequencies.put(c, charFrequencies.getOrDefault(c, 0) + 1);
        }

        // Step 3: Print the character frequencies
        System.out.println("Character frequencies (HashMap):");
        for (Map.Entry<Character, Integer> entry : charFrequencies.entrySet()) {
            System.out.println(entry.getKey() + ": " + entry.getValue());
        }
    }
}