Quick Interactive Web Pages with Java Sketchpad - Conclusion

Michael E. Mays

The story goes that when tools such as Visual Basic and Delphi became available, software developers would use them to develop prototypes for products they were considering, and then when crunch time came at the end of the project timeline they would just ship the prototype.  I started using JavaSketchpad to write online laboratories for a trigonometry course with the idea of writing Java applets of comparable functionality from scratch myself, but for the most part I have stuck with the original JavaSketchpad prototypes For example, here is the JavaSketchpad version of an activity to manipulate the vertices of a right triangle, with the goal of calculating values of trig functions directly:

Sorry, this page requires a Java-compatible web browser.

This applet was generated in Sketchpad by saving the sketch as an HTML file. (Here is the gsp file to generate the sketch.)  The following applet shows the same idea implemented from scratch:

The Java applet was developed in the Integrated Development Environment Visual Cafe 4.5 (zipped Visual Cafe project files). Visual Cafe has been developed and distributed by Symantec and then by WebGain, but its current status is unclear.

So which applet is better?  There is a smoothness to the JavaSketchpad applet that the IDE applet lacks.  IDE has a distracting flicker when the points are moved, and needs to be refreshed when the applet moves offscreen or is covered up.  On the other hand, I could label the line segments in IDE without displaying midpoints as I had to in JSP, and I easily implemented a units-changing feature.   All the cosmetic objections to either version are probably fixable with a little more understanding of the platform, but there are two differences that are not:

  1. It took an hour or so to write the JavaSketchpad applet, and a couple of days to write the IDE version.  I find myself getting faster in Java with practice, but I can't see myself ever getting that fast.

  2. If I wanted to publish the applet for profit, say in a textbook ancillary, the Java license from Sun makes the IDE version mine, but the JavaSketchpad version is by default limited to non-profit use.

Students using the lab don't seem to care which version they use.  If you know how to use The Geometer's Sketchpad®, JavaSketchpad is certainly worth exploring as a way to port sketches to applets.  As additional GSP features are incorporated into JavaSketchpad, it will become even more useful.