});
columns.add(new PropertyColumn<Contact, String>(new Model<>("Home Phone"), "homePhone"));
columns.add(new PropertyColumn<Contact, String>(new Model<>("Cell Phone"), "cellPhone"));
DataTable dataTable = new DefaultDataTable<>("table", columns,
new SortableContactDataProvider(), 8);
dataTable.addBottomToolbar(new ExportToolbar(dataTable).addDataExporter(new CSVDataExporter()));
add(dataTable);
DataTable tableWithColGroup = new DataTable<>("tableWithColGroup", columns,
new SortableContactDataProvider(), 8);
add(tableWithColGroup);
ColGroup colgroup = tableWithColGroup.getColGroup();
colgroup.add(AttributeModifier.append("style", "border: solid 1px green;"));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: lightblue;")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: lightgreen")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: pink")));
colgroup.addCol(colgroup.new Col(AttributeModifier.append("style", "background-color: yellow")));