Java code for using IvParameterSpec, AES/CFB/PKCS5Padding with SecureRandom for encryption and decryption

AESUtil.java

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;
import java.util.Base64;

public class AESUtil {
    private static final String ALGORITHM = "AES";
    private static final String CIPHER_ALGORITHM = "AES/CFB/PKCS5Padding";
    private static final int KEY_SIZE = 128;
    private static final int IV_SIZE = 16;

    public static String encrypt(String key, String plainText) throws Exception {
        byte[] keyBytes = key.getBytes();
        SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, ALGORITHM);

        SecureRandom secureRandom = new SecureRandom();
        byte[] iv = new byte[IV_SIZE];
        secureRandom.nextBytes(iv);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] encrypted = cipher.doFinal(plainText.getBytes());

        byte[] encryptedWithIV = new byte[iv.length + encrypted.length];
        System.arraycopy(iv, 0, encryptedWithIV, 0, iv.length);
        System.arraycopy(encrypted, 0, encryptedWithIV, iv.length, encrypted.length);

        return Base64.getEncoder().encodeToString(encryptedWithIV);
    }

    public static String decrypt(String key, String encryptedText) throws Exception {
        byte[] encryptedWithIV = Base64.getDecoder().decode(encryptedText);
        byte[] iv = new byte[IV_SIZE];
        System.arraycopy(encryptedWithIV, 0, iv, 0, iv.length);

        byte[] encrypted = new byte[encryptedWithIV.length - iv.length];
        System.arraycopy(encryptedWithIV, iv.length, encrypted, 0, encrypted.length);

        byte[] keyBytes = key.getBytes();
        SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, ALGORITHM);

        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

        Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] decrypted = cipher.doFinal(encrypted);

        return new String(decrypted);
    }
}


public static void main(String[] args) throws Exception {
    String key = "1234567890123456";
    String plainText = "Hello, world!";

    String encryptedText = AESUtil.encrypt(key, plainText);
    String decryptedText = AESUtil.decrypt(key, encryptedText);

    System.out.println("Plain text: " + plainText);
    System.out.println("Encrypted text: " + encryptedText);
    System.out.println("Decrypted text: " + decryptedText);
}