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.
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package org.bouncycastle.asn1;


Marker interface for CHOICE objects - if you implement this in a role your
own object any attempt to tag the object implicitly will convert the tag to
an explicit one as the encoding rules require.


If you use this interface your class should also implement the getInstance()
pattern which takes a tag object and the tagging mode used.



X.690


8: Basic encoding rules


8.13 Encoding of a choice value 



The encoding of a choice value shall be the same as the encoding of a value of the chosen type.


NOTE 1 — The encoding may be primitive or constructed depending on the chosen type.




NOTE 2 — The tag used in the identifier octets is the tag of the chosen type,
as specified in the ASN.1 definition of the choice type.



/**
 * Marker interface for CHOICE objects - if you implement this in a role your
 * own object any attempt to tag the object implicitly will convert the tag to
 * an explicit one as the encoding rules require.
 * <p>
 * If you use this interface your class should also implement the getInstance()
 * pattern which takes a tag object and the tagging mode used.
 * </p>
 * <p><b>X.690</b></p>
 * <p><b>8: Basic encoding rules</b></p>
 * <p><b>8.13 Encoding of a choice value </b></p>
 * <p>
 * The encoding of a choice value shall be the same as the encoding of a value of the chosen type.
 * <blockquote>
 * NOTE 1 &mdash; The encoding may be primitive or constructed depending on the chosen type.
 * </blockquote>
 * <blockquote>
 * NOTE 2 &mdash; The tag used in the identifier octets is the tag of the chosen type,
 * as specified in the ASN.1 definition of the choice type.
 * </blockquote>
 */
public interface ASN1Choice
{
    // marker interface
}