Each ui component class is available with its fluent counter part working out-of-the-box. Each setter has also its fluent version prefixed with the word "with" instead of "set". Each fluent class implements a fluent interface which adds the fluent methods. Therefore, it's easy to add fluent functionality to an existing component : just implement the right interface. Lets say you have a custom ComboBox doing fancy stuff in your project and you want to add fluent way to code it. Implement the FluentComboBox interface.