Take a look at the new interface:

As you can see, now the component is displayed as an assortment of checkboxes and the getValue method (of both OptionGroup and Property) returns a Java Collection (actually a Set). This happens when we activate multiselect mode.

Try changing the OptionGroup example application to show a message informing whether the answer is correct or not. Here is a quick hint: cast the value to a Java Set instance.

Instead of the OptionGroup component we can use TwinColSelect. We can change OptionGroup for TwinColSelect in the previous example:

TwinColSelect og = new TwinColSelect(
    "Two kinds of EJBs in Java EE are:", answers);

With this, we get an interesting component for selection:

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Vaadin includes a nice date/time picker with multiple configuration options. You can add a date picker using this:

DateField dateField = new DateField("Select a date");

This will display a field to directly type the date and a button to open a convenient calendar:

The getValue method of DateField returns a java.util.Date object. You can configure the resolution of DateField. For example, to allow users select only a year, we can do this:

dateField.setResolution(Resolution.YEAR);

This will show a more restrictive component:

A date format can be specified using the setDateFormat method:

dateField.setDateFormat("yyyy-MM-dd");