Java PKCS7 signature

GenPKCS.java

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.math.BigInteger;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.cert.X509Certificate;
import java.util.Enumeration;

import sun.security.pkcs.ContentInfo;
import sun.security.pkcs.PKCS7;
import sun.security.pkcs.SignerInfo;
import sun.security.util.DerOutputStream;
import sun.security.util.DerValue;
import sun.security.x509.AlgorithmId;
import sun.security.x509.X500Name;

public class GenPKCS {

    static final String STORENAME = "c:/fileName.p12";
    static final String STOREPASS = "password";

    public static void main(String[] args) throws Exception{

        //First load the keystore object by providing the p12 file path
        KeyStore clientStore = KeyStore.getInstance("PKCS12");
        //replace testPass with the p12 password/pin
        clientStore.load(new FileInputStream(STORENAME), STOREPASS.toCharArray());

        Enumeration<String> aliases = clientStore.aliases();
        String aliaz = "";
        while(aliases.hasMoreElements()){
            aliaz = aliases.nextElement();
            if(clientStore.isKeyEntry(aliaz)){
                break;
            }
        }
        X509Certificate c = (X509Certificate)clientStore.getCertificate(aliaz);

        //Data to sign
        byte[] dataToSign = "SigmaWorld".getBytes();
        //compute signature:
        Signature signature = Signature.getInstance("Sha1WithRSA");
        signature.initSign((PrivateKey)clientStore.getKey(aliaz, STOREPASS.toCharArray()));
        signature.update(dataToSign);
        byte[] signedData = signature.sign();

        //load X500Name
        X500Name xName      = X500Name.asX500Name(c.getSubjectX500Principal());
        //load serial number
        BigInteger serial   = c.getSerialNumber();
        //laod digest algorithm
        AlgorithmId digestAlgorithmId = new AlgorithmId(AlgorithmId.SHA_oid);
        //load signing algorithm
        AlgorithmId signAlgorithmId = new AlgorithmId(AlgorithmId.RSAEncryption_oid);

        //Create SignerInfo:
        SignerInfo sInfo = new SignerInfo(xName, serial, digestAlgorithmId, signAlgorithmId, signedData);
        //Create ContentInfo:
        ContentInfo cInfo = new ContentInfo(ContentInfo.DIGESTED_DATA_OID, new DerValue(DerValue.tag_OctetString, dataToSign));
        //Create PKCS7 Signed data
        PKCS7 p7 = new PKCS7(new AlgorithmId[] { digestAlgorithmId }, cInfo,
                new java.security.cert.X509Certificate[] { c },
                new SignerInfo[] { sInfo });
        //Write PKCS7 to bYteArray
        ByteArrayOutputStream bOut = new DerOutputStream();
        p7.encodeSignedData(bOut);
        byte[] encodedPKCS7 = bOut.toByteArray();
    }
}