MD5.java

package com.thealgorithms.hashes;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Scanner;

/**
 * The MD5 class provides a method to generate the MD5 hash for a given string.
 * MD5 (Message Digest Algorithm 5) is a widely used cryptographic hash function that produces
 * a 128-bit (16-byte) hash value. It is commonly used for checksums and data integrity,
 * although it is no longer considered secure for cryptographic purposes.
 * 
 * @see <a href="https://en.wikipedia.org/wiki/MD5">MD5 on Wikipedia</a>
 */
public class MD5 {

    /**
     * Generates the MD5 hash of the input string.
     *
     * @param input the string to be hashed
     * @return the MD5 hash as a hexadecimal string
     */
    public static String getMd5(String input) {
        try {
            // Create a MessageDigest instance for MD5
            MessageDigest md = MessageDigest.getInstance("MD5");

            // Compute the MD5 digest of the input string
            byte[] messageDigest = md.digest(input.getBytes());

            // Convert the byte array into a BigInteger to get the hash in hexadecimal format
            BigInteger no = new BigInteger(1, messageDigest);

            // Convert the BigInteger to a hexadecimal string
            String hashtext = no.toString(16);

            // Pad with leading zeros to ensure the hash is 32 characters long
            while (hashtext.length() < 32) {
                hashtext = "0" + hashtext;
            }

            // Return the generated MD5 hash
            return hashtext;
        } catch (NoSuchAlgorithmException e) {
            // Handle the case where MD5 algorithm is not available
            throw new RuntimeException(e);
        }
    }

    /**
     * The main method that takes user input, computes its MD5 hash, and prints the result.
     *
     * @param args command-line arguments
     * @throws NoSuchAlgorithmException if the MD5 algorithm is not available
     */
    public static void main(String args[]) throws NoSuchAlgorithmException {
        // Create a Scanner object to read input from the user
        Scanner scanner = new Scanner(System.in);

        // Prompt the user to enter a string to hash
        System.out.print("Enter the string to hash: ");

        // Read the input string from the user
        String s = scanner.nextLine();

        // Compute the MD5 hash of the input string and print it
        System.out.println("Your HashCode Generated by MD5 is: " + getMd5(s));

        // Close the Scanner object
        scanner.close();
    }
}