import javax.swing.JFrame; import java.awt.Graphics; import java.awt.Color; class Program01 extends JFrame { Program01() { setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setSize(400, 300); setVisible(true); } public static void main(String args[]) { new Program01(); } @Override public void paint(Graphics g) { g.setColor(Color.BLUE); g.fillRect(30, 30, 100, 30); } }