The file start.gp from the handouts page contains a script for gnuplot to get you started. Once you generate a postscript file, use the command open file.ps to open it in a viewer. You can print it to the printer using the lpr file.ps command.
To practice, plot functions that are O(1), O(n), O(n^2). In addition, you can copy the file unknown.dat and plot the data in that file. (What do you think it represents?)
long startTime = System.currentTimeMillis(); // run test here long endTime = System.currentTimeMillis(); long duration = endTime - startTime;