if its a simple x vs f(x) plot, your best option is to simply save to a file (say myplot.png), then open the file in a program that autoupdates on change - this will always give you the latest plot that is generated.
if you have more complicated plots (and cannot use a gui), then your best option is to export the data from maple and simply plot the data to a file via a separate program (you can write very simple code using matplotlib, or even use gnuplot or equivalent). This is painful because its a two-stage process, but you can automate it by using maple's "system" or "ssystem" calls...
looking at your last screenshot, i should note that of course the best way forward is to know more about what you need to do. For example, instead of calling every command separately from java, it might easier to simply create a maple script (i.e. a text file with a .mpl extension) and call that. One can easily pass variables to such a script using the -c flag. See this post for an example: