http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.pkcs.bc;

import java.io.IOException;

import org.bouncycastle.asn1.pkcs.CertificationRequest;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.crypto.util.PublicKeyFactory;
import org.bouncycastle.pkcs.PKCS10CertificationRequest;
import org.bouncycastle.pkcs.PKCSException;

public class BcPKCS10CertificationRequest
    extends PKCS10CertificationRequest
{
    public BcPKCS10CertificationRequest(CertificationRequest certificationRequest)
    {
        super(certificationRequest);
    }

    public BcPKCS10CertificationRequest(byte[] encoding)
        throws IOException
    {
        super(encoding);
    }

    public BcPKCS10CertificationRequest(PKCS10CertificationRequest requestHolder)
    {
        super(requestHolder.toASN1Structure());
    }

    public AsymmetricKeyParameter getPublicKey()
        throws PKCSException
    {
        try
        {
            return PublicKeyFactory.createKey(this.getSubjectPublicKeyInfo());
        }
        catch (IOException e)
        {
            throw new PKCSException("error extracting key encoding: " + e.getMessage(), e);
        }
    }
}