drawing - How to draw a directed arrow line in Java?

Question

I want to draw a directed arrow line through Java.

At present, I am using java.awt.Line2D.Double class to draw a line

g2.setStroke(new BasicStroke(2.0f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL)); // g2 is an instance of Graphics2D
g2.draw(new Line2D.Double(x1,y1,x2,y2));

But only the line appears and no directed arrow appears. BasicStroke.Join_BEVEL is used to draw a directed arrow. It is applied when two line segments meet.

The line I am drawing meets the border of a rectangle but no directed arrow is drawn. Only a simple line is drawn.

Is there anything I am missing?

Answer 1

Although Pete's post is awesomely comprehensive, I'm using this method to draw a very simple line with a little triangle at its end.

// create an AffineTransform 
// and a triangle centered on (0,0) and pointing downward
// somewhere outside Swing's paint loop
AffineTransform tx = new AffineTransform();
Line2D.Double line = new Line2D.Double(0,0,100,100);

Polygon arrowHead = new Polygon();  
arrowHead.addPoint( 0,5);
arrowHead.addPoint( -5, -5);
arrowHead.addPoint( 5,-5);

// [...]
private void drawArrowHead(Graphics2D g2d) {  
    tx.setToIdentity();
    double angle = Math.atan2(line.y2-line.y1, line.x2-line.x1);
    tx.translate(line.x2, line.y2);
    tx.rotate((angle-Math.PI/2d));  

    Graphics2D g = (Graphics2D) g2d.create();
    g.setTransform(tx);   
    g.fill(arrowHead);
    g.dispose();
}