You must have heard the old maxim that there are lies, damned lies, statistics and Excel charts - well, anyone who's ever tried to do any kind of serious reporting of statistics on the web knows that you need to be able to produce good graphs. For years there have been libraries such as JFreeChart that do a reasonable job of graph-drawing in static image way, in recent years arrival of Google Analytics (google finance's price history chart e.g.) raised the quality bar substantially. Suddenly everyone including your line manager wanted fancy line graphs that show the numbers represented by each point when you roll the mouse along the line (I am not going to use google charts as it requires internet connection to draw charts. If your application is installed in some secured environment where the outside connectivity is not allowed than you are in big trouble).