Skip to content

Tag: interface

Not able to create generic bounded class objects with interface

I am trying to use bounded types with generics to create generic objects of subclasses (these implement an interface). But I am getting type mismatch errors when initializing objects with the subclasses. Here is the interface: Here’s the class that implements this interface: Now I created 2 classes (SegmentPageScanResult and ItemProcessor) with the bounded generic type as: and When I

Creating an object based on the interface

I have class Button in package “pl.components” and I created interface IButoon in package “pl.icomponents”. I would like to create a button based on this interface. This button only has methods that are in the interface. So, I guess when I do Then my ibutton will only be able to use setToolTip. The only problem I have to do is

How can I override object methods inside interface?

All classes in java extend the Object class implicitly. But that doesn’t concern interfaces. Interfaces can only extend other interfaces, but no classes. However, I can override object class methods inside my interface. Can you please explain in simple words how is this even possible? Is there any use case for this? Answer Interface is a just contract. It says

Selecting default implementation from indirectly inherited Interface not working

I have 4 Classes that look like this: Why can’t I access the default implementation coming from extending Bar? Answer BarImpl can not invoke Foo’s default method explicitly, as BarImpl is not directly implementing Foo. It’s extending Bar which directly implements Foo, hence, it’s Bar’s decision to override Foo’s default method or not. BarImpl can only invoke Bar’s isEmpty() method

Using an Interface as a super type for Enum classes – problem with accessing Enum-specific methods

I’ve been attempting to implement an interface in my enums in order to have rules for a simulation I’m making. I am trying to access enum-methods such as values() and ordinal() (on objects). However, even with upper-bounding my classes with my interface name, I still cannot access these methods without overriding them in my interface, which won’t work. I’m trying

How to cast an object of an ArrayList of objects (of type superclass) to an object of type subclass

If I have a superclass, let’s call it Car, with the constructor parameters String name, String color, double wheelSize, and a subclass of this, let’s call it Truck, with the constructor parameters String name, String color, double wheelSize, and double truckBedArea, and in the subclass (Truck), I have a method called modifyCar with the paramaters Car car, String newName, String