扩展抽象类的类

Question

I have a problem, i have abstract class which implements interface, and one more class which extends this first abstract class, but i got an error it says that i my second class must inherit methods from interface, and i dont want that, i also can change it to abstract class too, but then i can't call constructor from that class in some third class, how can i fix this? I searched for answer on internet but couldnt find it, and i dont understand abstract classes rly good so i can't solve it.Please help (ps sorry for my english, it is really bad)

Edit: I have an assignment where it is requiered that my second class needs to extend abstract class, and i am implementing interface because they also gave me main class in which they are making object from constructor in my second class and then they are using it with type of interface, i dont know if this makes any sense, code is pretty long, but i will give some lines: Here is my main class (NationalTeam bulgaria = new NationalTeam("Bulgaria", Formation.F352, "Bulgaria"); nationalManager.setManagingTeam(bulgaria);) (bulgaria must be type of interface), also here is my constructor from second class which extends abstract class:(public NationalTeam(String name,Formation formation,String country){ super(name,formation); this.country=country; })

Answer 1

Abstract class:Abstract classes may have abstract methods which means methods are methods without implementations.

when you are extending a abstract class A, methods of class A must be implemented by your subclass lets say B unless you make your child class B an anstract class.

Answer 2

You need to think how want to design the system not how compiler forces you.

If design says second class should be abstract then do it and then ultimately implement your abstract methods in your implementation.

On the other way, if second class is your implementation not abstract, the you have to provide implementation to make object of it

Answer 3

my second class must inherit methods from interface, and i dont want that

Really? Then why did you declare the interface in the first place? Why the abstract class needs to implement the interface?

Interfaces are supposed to be a higher level of abstraction. It is a contract between the client code and the library. It creates a interface between the client code and the library. It's like saying "I have the abilities to do the things the interface requires me to do". And you say you don't want to?

So there are two good ways and one bad way to fix this:

Good

1. Don't extend the abstract class. Because if you do, it probably does not make sense.

2. The abstract class don't extend the interface.

Bad ( This is really really bad )

Add the methods in the interface and leave the body blank or return a random value. Again, don't do this if you don't have to .