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.cms;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.cms.CMSObjectIdentifiers;


a class representing null or absent content.

/**
 * a class representing null or absent content.
 */
public class CMSAbsentContent
    implements CMSTypedData, CMSReadable
{
    private final ASN1ObjectIdentifier type;

    public CMSAbsentContent()
    {
        this(CMSObjectIdentifiers.data);
    }

    public CMSAbsentContent(
        ASN1ObjectIdentifier type)
    {
        this.type = type;
    }

    public InputStream getInputStream()
    {
        return null;
    }

    public void write(OutputStream zOut)
        throws IOException, CMSException
    {
        // do nothing
    }

    public Object getContent()
    {
        return null;
    }

    public ASN1ObjectIdentifier getContentType()
    {
        return type;
    }
}