为什么这样做？ （Java，Graphics对象）

Here's my code:

这是我的代码:

public void paint(Graphics g) {

    Graphics2D g2 = (Graphics2D) g;
    g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);

    g.drawString("This is my string", 200, 200);
}
public void paint(G