差分

==Swing レイアウト 2==

*FlowLayout

c.gridwidth = 2; // ↓ 列数設定

c.gridx = buttonPos[i][0];

c.gridy = buttonPos[i][1];

final GridLayout gridLayout = new GridLayout(3,3);

final JPanel gridPanel = new JPanel(gridLayout);

gridPanel.add(new JButton(String.valueOf(i)));

}