How to check if a PDF is Password Protected or not

I am trying to use iText's PdfReader to check if a given PDF file is password protected or not, but am getting this exception:

Exception in thread "Main Thread" java.lang.NoClassDefFoundError:org/bouncycastle/asn1/ASN1OctetString

But when testing the same code against a non-password protected file it runs fine. Here is the complete code:

try {
    PdfReader pdf = new PdfReader("C:\\abc.pdf");
} catch (IOException e) {
    e.printStackTrace();
}