Remove Item From Table?

I'm trying to make a calendar that, when you click on the date, the result are stored in a map and visualized in a table that refers to a container.

I successfully created the map mechanism, but I have a problem on the list....

I add the rows in this way:

Object newItemId = container.addItem();
Item riga = container.getItem(newItemId);
riga.getItemProperty("Timestamp").setValue(fara);
riga.getItemProperty("Date").setValue(asa);
.
How can I delete a row in the list, when all I have in input is the "Timestamp" information, in a Long value?

BTY, I'm using NetBeans with Vaadin extension