JListでウィークカレンダーを作成してヒートマップを表示する

JList<Contribution> weekList = new JList<Contribution>() {
  @Override public void updateUI() {
    setCellRenderer(null);
    super.updateUI();
    setLayoutOrientation(JList.VERTICAL_WRAP);
    setVisibleRowCount(DayOfWeek.values().length); // ensure 7 rows in the list
    setFixedCellWidth(size.width);
    setFixedCellHeight(size.height);
    setCellRenderer(new ContributionListRenderer());
    getSelectionModel().setSelectionMode(ListSelectionModel.SINGLE_INTERVAL_SELECTION);
    setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 2));
  }
};
// ...
private class ContributionListRenderer implements ListCellRenderer<Contribution> {
  private final Icon emptyIcon = new ColorIcon(Color.WHITE);
  private final ListCellRenderer<? super Contribution> renderer
    = new DefaultListCellRenderer();
  @Override public Component getListCellRendererComponent(
      JList<? extends Contribution> list, Contribution value, int index,
      boolean isSelected, boolean cellHasFocus) {
    JLabel l = (JLabel) renderer.getListCellRendererComponent(
        list, null, index, isSelected, cellHasFocus);
    if (value.date.isAfter(currentLocalDate)) {
      l.setIcon(emptyIcon);
      l.setToolTipText(null);
    } else {
      l.setIcon(activityIcons.get(value.activity));
      String actTxt = value.activity == 0 ? "No" : Objects.toString(value.activity);
      l.setToolTipText(actTxt + " contribution on " + value.date.toString());
    }
    return l;
  }
}