import java.awt.BasicStroke;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class MainClass extends JPanel {
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
BasicStroke bs = new BasicStroke(16.0f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_BEVEL);
g2.setStroke(bs);
g.drawLine(30, 20, 270, 20);
}
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.getContentPane().add(new MainClass());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
frame.setVisible(true);
}
}