How to read a password encrypted key with java?

I have private key stored in file in PKCS8 DER format and protected by password. What is the easiest way to read it?

Here is the code I use to load unencrypted one:

InputStream in = new FileInputStream(privateKeyFilename);
byte[] privateKeydata = new byte[in.available()];
in.read(privateKeydata);
in.close();
KeyFactory privateKeyFactory = KeyFactory.getInstance("RSA");
PKCS8EncodedKeySpec encodedKeySpec = new PKCS8EncodedKeySpec(privateKeydata);
PrivateKey privateKey = privateKeyFactory.generatePrivate(encodedKeySpec);

It works fine for unencrypted keys with the same specification. By the way, I am using BouncyCastle.

I can view this private key using following openssl command

openssl pkcs8 -in ./privatekey.key -inform DER -passin pass:thisismypass

Please, Help!!!

I,ve posted some solutions in my own answer to this topic. But I keep question unanswered in case anybody can help with making it work without extra library, just BouncyCastle.