IdCreator is a helper for creating unique id's in your Vaadin UI.
If you're doing TestBench or JMeter testing in your application, you have to set sane, unique id's for your UI components. But in a dynamic UI this can be more difficult than it needs to be.
IdCreator helps in this by creating "component paths" that are automatically used as id's. The component paths are created by using simple interfaces that your components can implement, so only the components you choose participate in building the full path for a single component.
As an example (from the demo), given the UI is set as the id path root, and there are id path components "container" and "innerlayout", calling IdCreator.setId(field, "textfield") would set "demoUI-container-child-0-innerlayout-textfield" as the id of the field.