public static boolean isSubject( @Nonnull final Packet stanza )
    {
        final Element fmuc = stanza.getElement().element(FMUC);
        if (fmuc == null) {
            throw new IllegalArgumentException( "Provided stanza must have an 'fmuc' child element (but does not).");
        }

        final boolean result = stanza instanceof Message && stanza.getElement().element("subject") != null;
        Log.trace( "Stanza from '{}' was determined to {} a stanza containing a MUC subject.", stanza.getFrom(), result ? "be" : "not be" );
        return result;
    }
Sends a stanza back to a remote, joining FMUC node that represents acceptance of a FMUC join request.

@param joinRequest The request to join that is being accepted.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/spi/FMUCHandler.java