Example: Character Frequency Counter in Java

// Character Frequency Counter
import java.util.Scanner;

// Main class containing the entry point of the program
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Step 1: Prompt user for input string
        System.out.print("Enter a string: ");
        String inputString = scanner.nextLine();

        // Step 2: Define the size of the frequency array
        // We assume extended ASCII characters (0-255).
        // For full Unicode, a HashMap would be more appropriate.
        int[] frequency = new int[256]; // Array to store character counts

        // Step 3: Iterate through the string using a for loop
        // For each character, increment its count in the frequency array.
        for (int i = 0; i < inputString.length(); i++) {
            char ch = inputString.charAt(i);
            // Convert character to its ASCII value and use as index
            frequency[ch]++;
        }

        // Step 4: Iterate through the frequency array to print results
        System.out.println("Character frequencies:");
        for (int i = 0; i < frequency.length; i++) {
            // Check if the character appeared at least once
            if (frequency[i] > 0) {
                // Convert the ASCII index back to a character
                System.out.println((char) i + ": " + frequency[i]);
            }
        }

        scanner.close();
    }
}