import java.awt.*;
import javax.swing.*;

class Guruguru extends JPanel {
  private int r = 50;
  private int x = 110, y = 70 ;
  private double theta = 0; // 角度

  public Guruguru() {
    setPreferredSize(new Dimension(200, 180));
    Timer timer = new Timer(30, e -> {
      theta += 0.02;
      x =  60 + (int)(r * Math.cos(theta)); 
      y = 100 - (int)(r * Math.sin(theta));
      repaint();
    });
    timer.start();
    JButton startBtn = new JButton("start");
    startBtn.addActionListener(e -> timer.start());
    JButton stopBtn = new JButton("stop");
    stopBtn.addActionListener(e -> timer.stop());
    setLayout(new FlowLayout());
    add(startBtn); add(stopBtn);
  }
  
  @Override
  public void paintComponent(Graphics g) {
    super.paintComponent(g); 
    g.drawString("Hello, World!", x, y);
  }
}
void main() {
  SwingUtilities.invokeLater(() -> {
    JFrame frame = new JFrame("ぐるぐる!");
    frame.add(new Guruguru());
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  });
}