说明：   JFreeChart是一组功能强大、灵活易用的Java绘图API，使用它可以生成多种通用性的报表，包括柱状图、饼图、曲线图、甘特图等
( JFreeChart is a powerful, flexible and easy to use Java graphics API, with which you can generate a variety of reports versatility, including bar charts, pie charts, graphs, Gantt charts, etc.)