How would I make a paste from java using the system clipboard?

Try this

public static void type(String characters) {
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
StringSelection stringSelection = new StringSelection( characters );
clipboard.setContents(stringSelection, instance);
//control+V is for pasting...
robot.keyPress(KeyEvent.VK_CONTROL);
robot.keyPress(KeyEvent.VK_V);
robot.keyRelease(KeyEvent.VK_V);
robot.keyRelease(KeyEvent.VK_CONTROL);
}

While the robot class would work, it's not as elegant as using the system clipboard directly, like this:

private void onPaste(){
    Clipboard c = Toolkit.getDefaultToolkit().getSystemClipboard();
    Transferable t = c.getContents(this);
    if (t == null)
        return;
    try {
        jtxtfield.setText((String) t.getTransferData(DataFlavor.stringFlavor));
    } catch (Exception e){
        e.printStackTrace();
    }//try
}//onPaste

You could use the robot class like this

try
{
    Robot r = new Robot();
    r.keyPress(KeyEvent.VK_CONTROL);
    r.keyPress(KeyEvent.VK_V);
    r.keyRelease(KeyEvent.VK_CONTROL);
    r.keyRelease(KeyEvent.VK_V);

}
catch(Exception e)
{

}