http://www.bouncycastle.org/java.html: The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.asn1;

class DERFactory
{
    static final ASN1Sequence EMPTY_SEQUENCE = new DERSequence();
    static final ASN1Set EMPTY_SET = new DERSet();

    static ASN1Sequence createSequence(ASN1EncodableVector v)
    {
        return v.size() < 1 ? EMPTY_SEQUENCE : new DLSequence(v);
    }

    static ASN1Set createSet(ASN1EncodableVector v)
    {
        return v.size() < 1 ? EMPTY_SET : new DLSet(v);
    }
}