Java tutorial
import java.awt.BasicStroke; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import javax.swing.JComponent; import javax.swing.JFrame; public class BasicDraw { public static void main(String[] args) { new BasicDraw(); } BasicDraw() { JFrame frame = new JFrame(); frame.add(new MyComponent()); frame.setSize(300, 300); frame.setVisible(true); } } class MyComponent extends JComponent { public void paint(Graphics g) { Graphics2D g2d = (Graphics2D) g; float strokeThickness = 5.0f; BasicStroke stroke = new BasicStroke(strokeThickness); g2d.setStroke(stroke); g2d.draw(new Rectangle(20, 20, 200, 200)); } }