import java.awt.Color; import java.awt.Graphics; import java.util.ArrayList; import java.util.List; import javax.swing.JPanel; public class BubblePanel extends JPanel { private final List<Bubble> bubbles; public BubblePanel() { bubbles = new ArrayList<>(); for (int rowIndex = 0; rowIndex < 10; rowIndex++) for (int columnIndex = 0; columnIndex < 20; columnIndex++) bubbles.add(new Bubble(100 + columnIndex * 60, 100 + rowIndex * 60, 28, Color.YELLOW)); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); for (final Bubble bubble : bubbles) bubble.paintComponent(g); } }