I have a class SimpHisto that takes in an array of generic type SL, and returns the size and the count of a specific element of that array. My code is provided down below. After I tried to run my code using the snippet down below… I get an error saying: Can someone please explain what’s wrong with…
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 (Seg…
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 se…
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 c…
Calling an abstract method from an interface without overriding it
I am working on a Java project and want to understand the source code before implementing mine into it. The problem im facing is, how can the source code uses the abstract method from an interface without actually overriding it? At first, I came to this statement: DeviceService deviceService = context.deviceS…
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 overr…
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 wi…
How to get the File from an Upload component in Vaadin
I’m new with Vaadin, and I don’t know how to get the File from the Upload component, I’m always having a server error. I don’t think I understand properly how this works. Any help will be welcome. This is my code. Answer Here’s a code sample from one of my projects FlieUploader.j…
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 …
Is there a faster way to create 12 buttons?
I am doing a task where I need to create a 3×4 GridLayout with 12 buttons. The task is when I click any of the buttons, all other buttons change the value to 1. Now, this is how I did it: My question is – is there a faster way to do this than just copying the same lines 12