THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
...
Replace it with standard Java 8 java.util.function.Supplier<T> which is virtually identical.
Deprecate org.apache.wicket.util.IContextProvider
Replace IContextProvider<T, C> with standard Java 8 java.util.function.Function<C, T> which is virtually identical.
As a consequence IPageManagerProvider, IPageRendererProvider and IRequestCycleProvider now override #apply() method instead of #get().
IGenericComponent's setter methods now return the current instance for method chaining
All specialization classes return their type.
AjaxFallback** components now use java.util.Optional
All AjaxFallback** components and the containers which use internally AjaxFallback** components, like AjaxTabbedPanel, RatingPanel and TableTree, have been reworked to pass Optional<AjaxRequestTarget> instead of just AjaxRequestTarget to their onXyz() callback methods. This way the application developer should not forget to check that the AjaxRequestTarget is not null.
Behavior changes
FormComponentPanel delegates the call to #clearInput to its FormComponent children
FormComponent#clearInput() has been made non-final, so that now containers like FormComponentPanel could override this method and call #clearInput() on its children of type FormComponent.
Removals
...