code: public void putMsgfunc(MsgListener listener, Object userhandle, int mask) throws LpSolveException {
  		msgListener = listener;
  		msgUserhandle = (listener != null) ? userhandle : null;
  		addLp(this);
  		registerMsgfunc(mask);
  	}
docs: Register an <code>MsgListener</code> for callback.
  
  @param listener the listener that should be called by lp_solve
  @param userhandle an arbitrary object that is passed to the listener on call