Java GUI draw tree by using random number

I want to change the code to randomize this tree's angle and length like this photo by using Random Number. Please help me!

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



@Override
public void paint(Graphics g) {
    g.setColor(Color.BLACK);
    int x1 = getRandomNumber(100, 400);
    int y1 = getRandomNumber(400, 800);
    double angle = getRandomNumber(-10, 70);
    int length = getRandomNumber(5, 15);
    drawTree(g, x1, y1, angle, length); 
}


 public int getRandomNumber(int min, int max) {
        return (int) ((Math.random() * (max - min)) + min);
    }


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

}

}