完整的程序参考

import javax.swing. * ;

import java.awt. * ;

public class sgratest {

public static void main(String[]args) {

JFrame frame = new JFrame();

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

JPanel jp = new JPanel() {

@ Override

public void paint(Graphics g) {

super.paint(g);

g.setColor(Color.RED);

g.fillArc(80, 80, 100, 100,0,270);

g.dispose();

}

};

frame.add(jp);

frame.setSize(300, 300);

frame.setVisible(true);

}

}

测试：