there are no functions that would draw a triangle for you, however you can use the polygon method in graphics to make any shape you like
heres how it works
int[] xPoints = {100,50,150};
int[] yPoints = {100,200,200};
g.drawPolygon(xPoints, yPoints, 3);
theres also fillPolygon in case you wish to color it in. You can find all the drawing methods
here
i notice ur setting the background color to black, make sure you set the draw color to something else cuz by defaults its black.
Damoun.H.