How can I make a shape transparent in Java?

Question

I want to make a shape transparant (the shape should be semi-opaque). How can I do this in Java? This is a part of my code:

protected void paintComponent(Graphics g) {
  super.paintComponent(g);
  g.setColor(Color.red);
  g.fillOval(40, 40, 40, 40);
}

Answer 1

The color you are currently using, Color.RED , does not use alpha, which is basically how transparent your color will be.

g.setColor(new Color(255, 0, 0, 125));

This will create a new color, using RGBA. The color I created uses 255 for red, 0 for blue and 0 for green. 125 is the alpha