Extends and Interface has same method with the same parameters but different return types

Question

In java I have to create a class that extends another class and implements an interface. This is the class I have to extend

public class Cell  {

    public void receiveRat(RatInterface pRat) {     
    
    } 
}

This is the interface that I have to implement

public interface HoleInterface {    
    public int[] receiveRat(RatInterface pRat);
}

I have made the class

public class Hole extends Cell  implements HoleInterface {

    public Hole() {
    
    }

    @Override
    public int[] receiveRat(RatInterface pRat) {
        // TODO Auto-generated method stub
        return null;    
    }

The int[] in the hole class doesn't work because Hole extends the Cell and Cell has a method like that with the return type void. What am I suppose to do?

Answer 1

As far as I know, that is not possible. The return types clash. What you could do, is either rename one of the methods to something like public void getRat(RatInterface pRat){...} or let Cell implement HoleInterface, removing the public void receiveRat(RatInterface pRat) {...} method and replacing it with the @Override public int[] receiveRat(RatInterface pRat) {...} method. If then Hole extends Cell, it indirectly also implements HoleInterface. Like this:

public class Cell implements HoleInterface {
    @Override
    public int[] receiveRat(RatInterface pRat) {
        return null;
    }

//Now indirectly implements HoleInterface through Cell
public class Hole extends Cell{
    public Hole() {
    
    }
    @Override
    public int[] receiveRat(RatInterface pRat) {
        return null;    
    }

But thats just an idea... How to fix your problem depends on the specific task or problem you want to solve.