如果java TimeSeries只包含一个值，则不显示任何值

Question

TimeSeries series = new TimeSeries("Year Chart",Month.class);
series.add(cal.getTime,500);
TimeSeriesCollection dataset = new TimeSeriesCollection(series);

也就是说，序列只包含一个值，它不能在图形上显示任何内容

TimeSeries series = new TimeSeries("Year Chart",Month.class);
series.add(cal.getTime,100);
series.add(cal.getTime,500);
TimeSeriesCollection dataset = new TimeSeriesCollection(series);

也就是说，当它包含多个值时，它会显示在图形上

如果我想显示值，即使序列只包含一个值，该怎么办