Java GUI draw tree using random number

How can I make this tree's angle and depth to be random by using 'random number'?

public class DrawTreeFrame extends JFrame {

public DrawTreeFrame() {
    setSize(800, 700);
    
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setVisible(true);
}

private void drawTree(Graphics g, int x1, int y1, double angle, int depth) {
    if(depth==0)
        return;
    int x2 = x1 + (int) (Math.cos(Math.toRadians(angle)) * depth * 10.0);
    int y2 = y1 + (int) (Math.sin(Math.toRadians(angle)) * depth * 10.0);
    g.drawLine(x1, y1, x2, y2);
    drawTree(g, x2, y2, angle-20, depth-1);
    drawTree(g, x2, y2, angle+20, depth-1);
}

@Override
public void paint(Graphics g) {
    g.setColor(Color.BLACK);
    drawTree(g, 400, 600, -90, 10);
}

public static void main(String[] args) {
    new DrawTreeFrame();

}

}