public class MyClass extends VerticalLayout {

    LocalDate[] date = {LocalDate.now(), LocalDate.now(), LocalDate.now()};
    Boolean[] isPresent = {true, false, false, true, true, false, false, true, true};
    Map<LocalDate, Boolean[]> trainingsMap = new HashMap<>();
    Grid<Map<LocalDate, Boolean[]>> grid = new Grid();
    Icon icon;

    public MyClass() {

        for (int i = 0; i < date.length; i++) {
            trainingsMap.put(date[i], isPresent);
        }

        for (Map.Entry<LocalDate, Boolean[]> entry : trainingsMap.entrySet()) {

            grid.addColumn(new ComponentRenderer<>(createIsPresent(entry.getValue()))
                    .setHeader(new LocalDateTimeRenderer<>(entry.getKey(), "dd/MM")));

            add(grid);
        }
    }

    private Component createIsPresent(Boolean[] isPresent) {
        for (Boolean b : isPresent) {
            if (b) {
                icon = UIUtils.createPrimaryIcon(VaadinIcon.CHECK);
            } else {
                icon = UIUtils.createDisabledIcon(VaadinIcon.CLOSE);
            }
        }
        return icon;
    }
}