GridBagLayoutを使ってレンガ状に配置

JPanel panel = new JPanel(new GridBagLayout());
panel.setBorder(BorderFactory.createTitledBorder("Brick Layout"));
GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridy = GridBagConstraints.RELATIVE;
for (int y = 0; y < YSIZE; y++) {
  // // c.gridy = GridBagConstraints.RELATIVE; // c.gridy = y;
  // int d = y & 0b1; // = y % 2 == 0 ? 0 : 1; // start x offset
  // if (d == 1) {
  //   c.gridwidth = 1;
  //   c.gridx = 0;
  //   panel.add(new JButton("a"), c);
  // }
  c.gridx = y & 0b1; // start x offset
  c.gridwidth = WIDTH;
  for (int x = 0; x < XSIZE; x++) {
    panel.add(new JButton(" "), c);
    c.gridx += WIDTH;
  }
  // if (d == 0) {
  //   c.gridwidth = 1;
  //   panel.add(new JButton("c"), c);
  // }
}
// GridBagLayout to create a board
// https://community.oracle.com/thread/1357310
// <dummy-row>
c.gridwidth = 1;
// c.gridy = GridBagConstraints.REMAINDER;
for (c.gridx = 0; c.gridx <= WIDTH * XSIZE; c.gridx++) {
  panel.add(Box.createHorizontalStrut(24), c);
}
// </dummy-row>