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>