LegendTitle legendTitle = chart.getLegend();
legendTitle.setItemFont(font);
legendTitle.setNotify(true);
The setNotify() method somehow alerts the different objects dependent on the LegentTitle and update it's state. If that is not called, nothing happens. If that method is set to true that means, the current change on the chart, specifically the LegentTitle, call all dependent objects and notify of this change and properly act on it.