Ok ho risolto eheheh vi posto qui il codice non si sa mai dovesse servire in futuro
codice:
  private static final String HEX_DIGITS = "0123456789abcdef";

  private static String toHexString(byte[] v) {
      StringBuffer sb = new StringBuffer(v.length * 2);
      for (int i = 0; i < v.length; i++) {
        int b = v[i] & 0xFF;
        sb.append(HEX_DIGITS.charAt(b >>> 4))
          .append(HEX_DIGITS.charAt(b & 0xF));
      }
      return sb.toString();
  }

  public static void main(String[] args) throws Exception{
    String improntaOriginale = "prova";//codifica PHP =189bbbb00c5f1fb7fba9ad9285f193d1                                       
    MessageDigest md = MessageDigest.getInstance("MD5");
    byte[] impronta = md.digest(improntaOriginale.getBytes("UTF-8"));//Cripta
    System.out.println("toHexString="+toHexString(impronta));
}