code: import java.awt.*;
  import javax.swing.*;
  
  public class UlamSpiral extends JPanel {
  
      Font primeFont = new Font("Arial", Font.BOLD, 20);
      Font compositeFont = new Font("Arial", Font.PLAIN, 16);
  
      public UlamSpiral() {
          setPreferredSize(new Dimension(640, 640));
          setBackground(Color.white);
      }
  
      private boolean isPrime(int n) {
          if (n <= 2 || n % 2 == 0)
              return n == 2;
          for (int i = 3; i * i <= n; i += 2)
              if (n % i == 0)
                  return false;
          return true;
      }
  
      @Override
      public void paintComponent(Graphics gg) {
          super.paintComponent(gg);
          Graphics2D g = (Graphics2D) gg;
          g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                  RenderingHints.VALUE_ANTIALIAS_ON);
  
          g.setStroke(new BasicStroke(2));
  
          double angle = 0.0;
          int x = 280, y = 330, dx = 1, dy = 0;
  
          g.setColor(getForeground());
          g.drawLine(x, y - 5, x + 50, y - 5);
  
          for (int i = 1, step = 1, turn = 1; i < 100; i++) {
  
              g.setColor(getBackground());
              g.fillRect(x - 5, y - 20, 30, 30);
              g.setColor(getForeground());
              g.setFont(isPrime(i) ? primeFont : compositeFont);
              g.drawString(String.valueOf(i), x + (i < 10 ? 4 : 0), y);
  
              x += dx * 50;
              y += dy * 50;
  
              if (i == turn) {
                  angle += 90.0;
  
                  if ((dx == 0 && dy == -1) || (dx == 0 && dy == 1))
                      step++;
  
                  turn += step;
  
                  dx = (int) Math.cos(Math.toRadians(angle));
                  dy = (int) Math.sin(Math.toRadians(-angle));
  
                  g.translate(9, -5);
                  g.drawLine(x, y, x + dx * step * 50, y + dy * step * 50);
                  g.translate(-9, 5);
              }
          }
      }
  
      public static void main(String[] args) {
          SwingUtilities.invokeLater(() -> {
              JFrame f = new JFrame();
              f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
              f.setTitle("Ulam Spiral");
              f.setResizable(false);
              f.add(new UlamSpiral(), BorderLayout.CENTER);
              f.pack();
              f.setLocationRelativeTo(null);
              f.setVisible(true);
          });
      }
  }
  