Memory-footprint combobox (search autocomplete)

Solution 1:

Vaadin 7 lacks built-in generic lazy backend support. Thus ComboBox loads all items at once. One of the main benefits of Vaadin 8 and other newer Vaadin versions over Vaadin 7 is added support for callbacks data providers, which makes it clearly better when implementing something you are trying to do.

With Vaadin 7 there exists mixed set of add-on solutions in Vaadin's Directory to tackle this short coming. Specific for your case is for example the AutocompleteField. There is also more generic solution of Lazy Query Container, that can be use with various components accepting container data source (Table, Grid and ComboBox).