如何更精确地绘制此形状？

Question

I am using Graphics2D to draw shapes eg rectangles. However, I have got the code working and it draws rectangles on my GUI, but the accuracy is way off and not the size I drag it to be (the get methods return ints by default). Also it seems like the shape size and the number of shapes is random every time I click on the panel.

int a,b,a2,b2;

public void MyPaintMethod(Graphics g) {
    Graphics2D g2D = (Graphics2D) g;
    Rectangle2D rectangle = new Rectangle2D.Double(a,b,a2,b2);
    g2D.draw(rectangle);    
    repaint();
}

public void mousePressed(MouseEvent e) {
    // ML
    a = e.getX();
    b = e.getY();
}

public void mouseReleased(MouseEvent e) {
    // ML
    a2 = e.getX();
    b2 = e.getY();
}

Answer 1

Rectangle2D is constructed with (x,y,width,height). You're giving it (x1,y1,x2,y2). Try:

Rectangle2D rectangle = new Rectangle2D.Double(a, b, a2-a, b2-b);