How can you verify the correctness of a password entered?

Checking the correctness of a password entered in Java usually involves several steps:

1. Obtaining the password from the user (for example, through a form).
2. Hashing the entered password using the same algorithm and salt as when it was stored.
3. Comparing the obtained hash with the hash stored in the database.

Example using MessageDigest for password hashing:

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

public class PasswordChecker {
    public static byte[] hashPassword(String password) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        return md.digest(password.getBytes());
    }

    public static boolean checkPassword(String inputPassword, byte[] storedHash) throws NoSuchAlgorithmException {
        byte[] inputHash = hashPassword(inputPassword);
        return Arrays.equals(inputHash, storedHash);
    }

    public static void main(String[] args) throws NoSuchAlgorithmException {
        String correctPassword = "secret123";
        byte[] storedHash = hashPassword(correctPassword);

        String userInput = "secret123";
        if (checkPassword(userInput, storedHash)) {
            System.out.println("Password is correct");
        } else {
            System.out.println("Incorrect password");
        }
    }
}

In real applications, it is recommended to use specialized libraries for password hashing, such as BCrypt, which take into account salts and make hashing more secure.