public void setSubject(String subject) {
        this.subject = subject;
    }
Sets the last subject that some occupant set to the room. This message will only be used
when loading a room from the database.

@param subject the last known subject of the room (cannot be {@code null}).
xmppserver/src/main/java/org/jivesoftware/openfire/muc/MUCRoom.java