Simple as the title states: Can you use only Java commands to take a screenshot and save it? Or, do I need to use an OS specific program to take the screenshot and then grab it off the clipboard?
Believe it or not, you can actually use java.awt.Robot
to "create an image containing pixels read from the screen." You can then write that image to a file on disk.
I just tried it, and the whole thing ends up like:
Rectangle screenRect = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
BufferedImage capture = new Robot().createScreenCapture(screenRect);
ImageIO.write(capture, "bmp", new File(args[0]));
NOTE: This will only capture the primary monitor. See GraphicsConfiguration for multi-monitor support.