jgnuplot is a Java library for interfacing with the gnuplot plotting package which outputs to X11, PostScript, PNG, GIF and other formats.
This library generates temporary gnuplot files which result in plots in specified output files. For more info, please see jgnuplot API documentation
Below are some examples that are distributed with gnuplot and which are implement using the jgnuplot library.
Below is a screenshot of jgnuplot.