Swing/DiagonalHeaderCellBorder のバックアップ(No.1)

int size = 32;
JTable table = new JTable(model) {
  @Override public void updateUI() {
    super.updateUI();
    setRowHeight(size);
    TableCellRenderer hr = new VerticalTableHeaderRenderer();
    TableColumnModel cm = getColumnModel();
    cm.getColumn(0).setHeaderRenderer(
        new DiagonallySplitHeaderRenderer());
    cm.getColumn(0).setPreferredWidth(size * 5);
    for (int i = 1; i < cm.getColumnCount(); i++) {
      TableColumn tc = cm.getColumn(i);
      tc.setHeaderRenderer(hr);
      tc.setPreferredWidth(size);
    }
  }
};
table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);

JScrollPane scroll = new JScrollPane(table);
scroll.setColumnHeader(new JViewport() {
  @Override public Dimension getPreferredSize() {
    Dimension d = super.getPreferredSize();
    d.height = size * 2;
    return d;
  }
});
// ...

class DiagonallySplitBorder extends MatteBorder {
  protected DiagonallySplitBorder(
      int top, int left, int bottom, int right, Color matteColor) {
    super(top, left, bottom, right, matteColor);
  }

  @Override public void paintBorder(
      Component c, Graphics g, int x, int y, int width, int height) {
    super.paintBorder(c, g, x, y, width, height);
    Graphics2D g2 = (Graphics2D) g.create();
    g2.translate(x, y);
    g2.setRenderingHint(
        RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
    g2.setPaint(getMatteColor());
    g2.drawLine(0, 0, c.getWidth() - 1, c.getHeight() - 1);
    g2.dispose();
  }
}