Aiuto con java

class SimpleCrypto {

   public static String encrypt(String seed, String cleartext) throws Exception {
           byte[] rawKey = getRawKey(seed.getBytes());
           byte[] result = encrypt(rawKey, cleartext.getBytes());
           return toHex(result);
   }
   
   public static String decrypt(String seed, String encrypted) throws Exception {
           byte[] rawKey = getRawKey(seed.getBytes());
           byte[] enc = toByte(encrypted);
           byte[] result = decrypt(rawKey, enc);
           return new String(result);
   }

   private static byte[] getRawKey(byte[] seed) throws Exception {
           KeyGenerator kgen = KeyGenerator.getInstance("AES");
           SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
           sr.setSeed(seed);
       kgen.init(128, sr); // 192 and 256 bits may not be available
       SecretKey skey = kgen.generateKey();
       byte[] raw = skey.getEncoded();
       return raw;
   }

   
   private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
       SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
           Cipher cipher = Cipher.getInstance("AES");
       cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
       byte[] encrypted = cipher.doFinal(clear);
           return encrypted;
   }

   private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
       SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
           Cipher cipher = Cipher.getInstance("AES");
       cipher.init(Cipher.DECRYPT_MODE, skeySpec);
       byte[] decrypted = cipher.doFinal(encrypted);
           return decrypted;
   }

   public static String toHex(String txt) {
           return toHex(txt.getBytes());
   }
   public static String fromHex(String hex) {
           return new String(toByte(hex));
   }
   
   public static byte[] toByte(String hexString) {
           int len = hexString.length()/2;
           byte[] result = new byte[len];
           for (int i = 0; i < len; i++)
                   result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
           return result;
   }

   public static String toHex(byte[] buf) {
           if (buf == null)
                   return "";
           StringBuffer result = new StringBuffer(2*buf.length);
           for (int i = 0; i < buf.length; i++) {
                   appendHex(result, buf[i]);
           }
           return result.toString();
   }
   private final static String HEX = "0123456789ABCDEF";
   private static void appendHex(StringBuffer sb, byte b) {
           sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
   }
   
}

SimpleCrypto.encrypt("password","stringa")
SimpleCrypto.decrypt("password","stringa_criptata")